bonding
DESCRIPTION
Bonding. How do compounds benefit society? Which type of compound is the most useful to you and why?. Octet Rule. In compounds, atoms tend to achieve noble gas electron configurations Metals lose to achieve octet in lower energy level Non-metals gain to get 8 if combine with metal - PowerPoint PPT PresentationTRANSCRIPT
1
Bonding
How do compounds benefit society
Which type of compound is the most useful to you and why
2
Octet Rule
In compounds atoms tend to achieve noble gas electron configurations Metals lose to achieve octet in lower energy level Non-metals gain to get 8 if combine with metal
or can share with other non-metals
Metal cation + non-metal anion
= ionic bond (chapter 7) 2 non-metals = covalent bond (chapter 8) 2 metals = metallic bond (also chapter 7)
3
81 Molecular Compounds
Covalent bonds Sharing of electrons to hold atoms together Between 2 non-metals Neutral Makes molecules Bond dissociation energy is the amount of energy
required to break a covalent bond between atoms A large bond dissociation energy corresponds to a
strong covalent bond Double and triple bonds are stronger than single cov bonds
4
Molecular compounds
Chemical formula = molecular formula Not lowest whole number just actual number of
atoms of each element Properties
Comprised of two or more non-metals Not good conductors of heat and electric current Lower melting and boiling points than ionic
Diatomic molecules Molecule of 2 identical atoms H2 O2 N2 Cl2 Br2 I2 F2
5
Nomenclature
The same elements can combine in multiple ways via different numbers of atoms to form different molecules Ex CO vs CO2
ndashide suffix on second element just like ionic Use prefixes to indicate number of each
Mono- di- tri- tetra- penta- hexa- hepta- octa- nona- deca-
No mono- for first element Ex carbon monoxide and carbon dioxide
6
Naming molecular compounds
Practice SiO2
Silicon dioxide SO3
sulfur trioxide XeF4
Xenon tetrafluoride Phosphorus pentachloride
PCl5 Dinitrogen monoxide
N2O
7
82 Nature of covalent bonding Still obeys octet rule
Share as many electrons as needed for 8 Single covalent bond
Share one pair of electrons (1 from each atom) Ex H-H
Double covalent bond Share two pairs of electrons (2 from each)
Ex O=O Triple covalent bond
Share 3 pairs of electrons (3 from each) Ex NequivN
Coordinate covalent bond Share pair of electrons (usually only 1) but both from 1 atom
Ex C + Ouml CequivO (often drawn C=O )
8
Recall electron configurations
Valence electrons Highest occupied energy level Largely determine chemical properties Corresponds to American group number
Exception = He Used for chemical bonds Shown in electron-dot structuresdiagrams
Ex H
9
Electron Dot Diagrams
Practice Na F He Cl Mg
S B Li Ne
C Kr N Si O
Al P Ca Find a
trend
10
Structures
Dot structures can be made for covalent bonds Place shared electrons between the 2 symbols
either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in cov bond Structural formulas use dashes but also
show spatial arrangement of atoms
How Covalent Bonds Form
Draw the Lewis dot diagrams for all the atoms in CH4
Draw 1 carbon diagram
Draw 4 hydrogen diagrams
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
C
Bonding in Methane
H HH
H
C
Bonding in Methane
HH
HH
Draw the following compounds
PCl3 H2O
SF2 AlCl3
Do NowGet out your homework to be stamped and
be prepared to answer
What is a covalent bond
What types of elements do covalent bonds form between
What are valence electrons
How many electrons are in a bond
Single Bond
Two electrons are shared between two atoms
1 electron pair
Represented by 1 line between the atoms
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Double Bond
Four electrons are shared between two atoms
2 electron pairs
Represented by 2 lines between the atoms
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Double bonds Try ItDouble bonds Try It
Draw the Lewis dot diagram for
O3
CO2
CF2S
Triple Bond
Six electrons are shared between two atoms
3 electron pairs
Represented by 3 lines between the atoms
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
2
Octet Rule
In compounds atoms tend to achieve noble gas electron configurations Metals lose to achieve octet in lower energy level Non-metals gain to get 8 if combine with metal
or can share with other non-metals
Metal cation + non-metal anion
= ionic bond (chapter 7) 2 non-metals = covalent bond (chapter 8) 2 metals = metallic bond (also chapter 7)
3
81 Molecular Compounds
Covalent bonds Sharing of electrons to hold atoms together Between 2 non-metals Neutral Makes molecules Bond dissociation energy is the amount of energy
required to break a covalent bond between atoms A large bond dissociation energy corresponds to a
strong covalent bond Double and triple bonds are stronger than single cov bonds
4
Molecular compounds
Chemical formula = molecular formula Not lowest whole number just actual number of
atoms of each element Properties
Comprised of two or more non-metals Not good conductors of heat and electric current Lower melting and boiling points than ionic
Diatomic molecules Molecule of 2 identical atoms H2 O2 N2 Cl2 Br2 I2 F2
5
Nomenclature
The same elements can combine in multiple ways via different numbers of atoms to form different molecules Ex CO vs CO2
ndashide suffix on second element just like ionic Use prefixes to indicate number of each
Mono- di- tri- tetra- penta- hexa- hepta- octa- nona- deca-
No mono- for first element Ex carbon monoxide and carbon dioxide
6
Naming molecular compounds
Practice SiO2
Silicon dioxide SO3
sulfur trioxide XeF4
Xenon tetrafluoride Phosphorus pentachloride
PCl5 Dinitrogen monoxide
N2O
7
82 Nature of covalent bonding Still obeys octet rule
Share as many electrons as needed for 8 Single covalent bond
Share one pair of electrons (1 from each atom) Ex H-H
Double covalent bond Share two pairs of electrons (2 from each)
Ex O=O Triple covalent bond
Share 3 pairs of electrons (3 from each) Ex NequivN
Coordinate covalent bond Share pair of electrons (usually only 1) but both from 1 atom
Ex C + Ouml CequivO (often drawn C=O )
8
Recall electron configurations
Valence electrons Highest occupied energy level Largely determine chemical properties Corresponds to American group number
Exception = He Used for chemical bonds Shown in electron-dot structuresdiagrams
Ex H
9
Electron Dot Diagrams
Practice Na F He Cl Mg
S B Li Ne
C Kr N Si O
Al P Ca Find a
trend
10
Structures
Dot structures can be made for covalent bonds Place shared electrons between the 2 symbols
either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in cov bond Structural formulas use dashes but also
show spatial arrangement of atoms
How Covalent Bonds Form
Draw the Lewis dot diagrams for all the atoms in CH4
Draw 1 carbon diagram
Draw 4 hydrogen diagrams
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
C
Bonding in Methane
H HH
H
C
Bonding in Methane
HH
HH
Draw the following compounds
PCl3 H2O
SF2 AlCl3
Do NowGet out your homework to be stamped and
be prepared to answer
What is a covalent bond
What types of elements do covalent bonds form between
What are valence electrons
How many electrons are in a bond
Single Bond
Two electrons are shared between two atoms
1 electron pair
Represented by 1 line between the atoms
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Double Bond
Four electrons are shared between two atoms
2 electron pairs
Represented by 2 lines between the atoms
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Double bonds Try ItDouble bonds Try It
Draw the Lewis dot diagram for
O3
CO2
CF2S
Triple Bond
Six electrons are shared between two atoms
3 electron pairs
Represented by 3 lines between the atoms
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
3
81 Molecular Compounds
Covalent bonds Sharing of electrons to hold atoms together Between 2 non-metals Neutral Makes molecules Bond dissociation energy is the amount of energy
required to break a covalent bond between atoms A large bond dissociation energy corresponds to a
strong covalent bond Double and triple bonds are stronger than single cov bonds
4
Molecular compounds
Chemical formula = molecular formula Not lowest whole number just actual number of
atoms of each element Properties
Comprised of two or more non-metals Not good conductors of heat and electric current Lower melting and boiling points than ionic
Diatomic molecules Molecule of 2 identical atoms H2 O2 N2 Cl2 Br2 I2 F2
5
Nomenclature
The same elements can combine in multiple ways via different numbers of atoms to form different molecules Ex CO vs CO2
ndashide suffix on second element just like ionic Use prefixes to indicate number of each
Mono- di- tri- tetra- penta- hexa- hepta- octa- nona- deca-
No mono- for first element Ex carbon monoxide and carbon dioxide
6
Naming molecular compounds
Practice SiO2
Silicon dioxide SO3
sulfur trioxide XeF4
Xenon tetrafluoride Phosphorus pentachloride
PCl5 Dinitrogen monoxide
N2O
7
82 Nature of covalent bonding Still obeys octet rule
Share as many electrons as needed for 8 Single covalent bond
Share one pair of electrons (1 from each atom) Ex H-H
Double covalent bond Share two pairs of electrons (2 from each)
Ex O=O Triple covalent bond
Share 3 pairs of electrons (3 from each) Ex NequivN
Coordinate covalent bond Share pair of electrons (usually only 1) but both from 1 atom
Ex C + Ouml CequivO (often drawn C=O )
8
Recall electron configurations
Valence electrons Highest occupied energy level Largely determine chemical properties Corresponds to American group number
Exception = He Used for chemical bonds Shown in electron-dot structuresdiagrams
Ex H
9
Electron Dot Diagrams
Practice Na F He Cl Mg
S B Li Ne
C Kr N Si O
Al P Ca Find a
trend
10
Structures
Dot structures can be made for covalent bonds Place shared electrons between the 2 symbols
either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in cov bond Structural formulas use dashes but also
show spatial arrangement of atoms
How Covalent Bonds Form
Draw the Lewis dot diagrams for all the atoms in CH4
Draw 1 carbon diagram
Draw 4 hydrogen diagrams
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
C
Bonding in Methane
H HH
H
C
Bonding in Methane
HH
HH
Draw the following compounds
PCl3 H2O
SF2 AlCl3
Do NowGet out your homework to be stamped and
be prepared to answer
What is a covalent bond
What types of elements do covalent bonds form between
What are valence electrons
How many electrons are in a bond
Single Bond
Two electrons are shared between two atoms
1 electron pair
Represented by 1 line between the atoms
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Double Bond
Four electrons are shared between two atoms
2 electron pairs
Represented by 2 lines between the atoms
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Double bonds Try ItDouble bonds Try It
Draw the Lewis dot diagram for
O3
CO2
CF2S
Triple Bond
Six electrons are shared between two atoms
3 electron pairs
Represented by 3 lines between the atoms
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
4
Molecular compounds
Chemical formula = molecular formula Not lowest whole number just actual number of
atoms of each element Properties
Comprised of two or more non-metals Not good conductors of heat and electric current Lower melting and boiling points than ionic
Diatomic molecules Molecule of 2 identical atoms H2 O2 N2 Cl2 Br2 I2 F2
5
Nomenclature
The same elements can combine in multiple ways via different numbers of atoms to form different molecules Ex CO vs CO2
ndashide suffix on second element just like ionic Use prefixes to indicate number of each
Mono- di- tri- tetra- penta- hexa- hepta- octa- nona- deca-
No mono- for first element Ex carbon monoxide and carbon dioxide
6
Naming molecular compounds
Practice SiO2
Silicon dioxide SO3
sulfur trioxide XeF4
Xenon tetrafluoride Phosphorus pentachloride
PCl5 Dinitrogen monoxide
N2O
7
82 Nature of covalent bonding Still obeys octet rule
Share as many electrons as needed for 8 Single covalent bond
Share one pair of electrons (1 from each atom) Ex H-H
Double covalent bond Share two pairs of electrons (2 from each)
Ex O=O Triple covalent bond
Share 3 pairs of electrons (3 from each) Ex NequivN
Coordinate covalent bond Share pair of electrons (usually only 1) but both from 1 atom
Ex C + Ouml CequivO (often drawn C=O )
8
Recall electron configurations
Valence electrons Highest occupied energy level Largely determine chemical properties Corresponds to American group number
Exception = He Used for chemical bonds Shown in electron-dot structuresdiagrams
Ex H
9
Electron Dot Diagrams
Practice Na F He Cl Mg
S B Li Ne
C Kr N Si O
Al P Ca Find a
trend
10
Structures
Dot structures can be made for covalent bonds Place shared electrons between the 2 symbols
either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in cov bond Structural formulas use dashes but also
show spatial arrangement of atoms
How Covalent Bonds Form
Draw the Lewis dot diagrams for all the atoms in CH4
Draw 1 carbon diagram
Draw 4 hydrogen diagrams
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
C
Bonding in Methane
H HH
H
C
Bonding in Methane
HH
HH
Draw the following compounds
PCl3 H2O
SF2 AlCl3
Do NowGet out your homework to be stamped and
be prepared to answer
What is a covalent bond
What types of elements do covalent bonds form between
What are valence electrons
How many electrons are in a bond
Single Bond
Two electrons are shared between two atoms
1 electron pair
Represented by 1 line between the atoms
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Double Bond
Four electrons are shared between two atoms
2 electron pairs
Represented by 2 lines between the atoms
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Double bonds Try ItDouble bonds Try It
Draw the Lewis dot diagram for
O3
CO2
CF2S
Triple Bond
Six electrons are shared between two atoms
3 electron pairs
Represented by 3 lines between the atoms
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
5
Nomenclature
The same elements can combine in multiple ways via different numbers of atoms to form different molecules Ex CO vs CO2
ndashide suffix on second element just like ionic Use prefixes to indicate number of each
Mono- di- tri- tetra- penta- hexa- hepta- octa- nona- deca-
No mono- for first element Ex carbon monoxide and carbon dioxide
6
Naming molecular compounds
Practice SiO2
Silicon dioxide SO3
sulfur trioxide XeF4
Xenon tetrafluoride Phosphorus pentachloride
PCl5 Dinitrogen monoxide
N2O
7
82 Nature of covalent bonding Still obeys octet rule
Share as many electrons as needed for 8 Single covalent bond
Share one pair of electrons (1 from each atom) Ex H-H
Double covalent bond Share two pairs of electrons (2 from each)
Ex O=O Triple covalent bond
Share 3 pairs of electrons (3 from each) Ex NequivN
Coordinate covalent bond Share pair of electrons (usually only 1) but both from 1 atom
Ex C + Ouml CequivO (often drawn C=O )
8
Recall electron configurations
Valence electrons Highest occupied energy level Largely determine chemical properties Corresponds to American group number
Exception = He Used for chemical bonds Shown in electron-dot structuresdiagrams
Ex H
9
Electron Dot Diagrams
Practice Na F He Cl Mg
S B Li Ne
C Kr N Si O
Al P Ca Find a
trend
10
Structures
Dot structures can be made for covalent bonds Place shared electrons between the 2 symbols
either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in cov bond Structural formulas use dashes but also
show spatial arrangement of atoms
How Covalent Bonds Form
Draw the Lewis dot diagrams for all the atoms in CH4
Draw 1 carbon diagram
Draw 4 hydrogen diagrams
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
C
Bonding in Methane
H HH
H
C
Bonding in Methane
HH
HH
Draw the following compounds
PCl3 H2O
SF2 AlCl3
Do NowGet out your homework to be stamped and
be prepared to answer
What is a covalent bond
What types of elements do covalent bonds form between
What are valence electrons
How many electrons are in a bond
Single Bond
Two electrons are shared between two atoms
1 electron pair
Represented by 1 line between the atoms
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Double Bond
Four electrons are shared between two atoms
2 electron pairs
Represented by 2 lines between the atoms
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Double bonds Try ItDouble bonds Try It
Draw the Lewis dot diagram for
O3
CO2
CF2S
Triple Bond
Six electrons are shared between two atoms
3 electron pairs
Represented by 3 lines between the atoms
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
6
Naming molecular compounds
Practice SiO2
Silicon dioxide SO3
sulfur trioxide XeF4
Xenon tetrafluoride Phosphorus pentachloride
PCl5 Dinitrogen monoxide
N2O
7
82 Nature of covalent bonding Still obeys octet rule
Share as many electrons as needed for 8 Single covalent bond
Share one pair of electrons (1 from each atom) Ex H-H
Double covalent bond Share two pairs of electrons (2 from each)
Ex O=O Triple covalent bond
Share 3 pairs of electrons (3 from each) Ex NequivN
Coordinate covalent bond Share pair of electrons (usually only 1) but both from 1 atom
Ex C + Ouml CequivO (often drawn C=O )
8
Recall electron configurations
Valence electrons Highest occupied energy level Largely determine chemical properties Corresponds to American group number
Exception = He Used for chemical bonds Shown in electron-dot structuresdiagrams
Ex H
9
Electron Dot Diagrams
Practice Na F He Cl Mg
S B Li Ne
C Kr N Si O
Al P Ca Find a
trend
10
Structures
Dot structures can be made for covalent bonds Place shared electrons between the 2 symbols
either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in cov bond Structural formulas use dashes but also
show spatial arrangement of atoms
How Covalent Bonds Form
Draw the Lewis dot diagrams for all the atoms in CH4
Draw 1 carbon diagram
Draw 4 hydrogen diagrams
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
C
Bonding in Methane
H HH
H
C
Bonding in Methane
HH
HH
Draw the following compounds
PCl3 H2O
SF2 AlCl3
Do NowGet out your homework to be stamped and
be prepared to answer
What is a covalent bond
What types of elements do covalent bonds form between
What are valence electrons
How many electrons are in a bond
Single Bond
Two electrons are shared between two atoms
1 electron pair
Represented by 1 line between the atoms
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Double Bond
Four electrons are shared between two atoms
2 electron pairs
Represented by 2 lines between the atoms
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Double bonds Try ItDouble bonds Try It
Draw the Lewis dot diagram for
O3
CO2
CF2S
Triple Bond
Six electrons are shared between two atoms
3 electron pairs
Represented by 3 lines between the atoms
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
7
82 Nature of covalent bonding Still obeys octet rule
Share as many electrons as needed for 8 Single covalent bond
Share one pair of electrons (1 from each atom) Ex H-H
Double covalent bond Share two pairs of electrons (2 from each)
Ex O=O Triple covalent bond
Share 3 pairs of electrons (3 from each) Ex NequivN
Coordinate covalent bond Share pair of electrons (usually only 1) but both from 1 atom
Ex C + Ouml CequivO (often drawn C=O )
8
Recall electron configurations
Valence electrons Highest occupied energy level Largely determine chemical properties Corresponds to American group number
Exception = He Used for chemical bonds Shown in electron-dot structuresdiagrams
Ex H
9
Electron Dot Diagrams
Practice Na F He Cl Mg
S B Li Ne
C Kr N Si O
Al P Ca Find a
trend
10
Structures
Dot structures can be made for covalent bonds Place shared electrons between the 2 symbols
either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in cov bond Structural formulas use dashes but also
show spatial arrangement of atoms
How Covalent Bonds Form
Draw the Lewis dot diagrams for all the atoms in CH4
Draw 1 carbon diagram
Draw 4 hydrogen diagrams
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
C
Bonding in Methane
H HH
H
C
Bonding in Methane
HH
HH
Draw the following compounds
PCl3 H2O
SF2 AlCl3
Do NowGet out your homework to be stamped and
be prepared to answer
What is a covalent bond
What types of elements do covalent bonds form between
What are valence electrons
How many electrons are in a bond
Single Bond
Two electrons are shared between two atoms
1 electron pair
Represented by 1 line between the atoms
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Double Bond
Four electrons are shared between two atoms
2 electron pairs
Represented by 2 lines between the atoms
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Double bonds Try ItDouble bonds Try It
Draw the Lewis dot diagram for
O3
CO2
CF2S
Triple Bond
Six electrons are shared between two atoms
3 electron pairs
Represented by 3 lines between the atoms
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
8
Recall electron configurations
Valence electrons Highest occupied energy level Largely determine chemical properties Corresponds to American group number
Exception = He Used for chemical bonds Shown in electron-dot structuresdiagrams
Ex H
9
Electron Dot Diagrams
Practice Na F He Cl Mg
S B Li Ne
C Kr N Si O
Al P Ca Find a
trend
10
Structures
Dot structures can be made for covalent bonds Place shared electrons between the 2 symbols
either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in cov bond Structural formulas use dashes but also
show spatial arrangement of atoms
How Covalent Bonds Form
Draw the Lewis dot diagrams for all the atoms in CH4
Draw 1 carbon diagram
Draw 4 hydrogen diagrams
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
C
Bonding in Methane
H HH
H
C
Bonding in Methane
HH
HH
Draw the following compounds
PCl3 H2O
SF2 AlCl3
Do NowGet out your homework to be stamped and
be prepared to answer
What is a covalent bond
What types of elements do covalent bonds form between
What are valence electrons
How many electrons are in a bond
Single Bond
Two electrons are shared between two atoms
1 electron pair
Represented by 1 line between the atoms
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Double Bond
Four electrons are shared between two atoms
2 electron pairs
Represented by 2 lines between the atoms
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Double bonds Try ItDouble bonds Try It
Draw the Lewis dot diagram for
O3
CO2
CF2S
Triple Bond
Six electrons are shared between two atoms
3 electron pairs
Represented by 3 lines between the atoms
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
9
Electron Dot Diagrams
Practice Na F He Cl Mg
S B Li Ne
C Kr N Si O
Al P Ca Find a
trend
10
Structures
Dot structures can be made for covalent bonds Place shared electrons between the 2 symbols
either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in cov bond Structural formulas use dashes but also
show spatial arrangement of atoms
How Covalent Bonds Form
Draw the Lewis dot diagrams for all the atoms in CH4
Draw 1 carbon diagram
Draw 4 hydrogen diagrams
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
C
Bonding in Methane
H HH
H
C
Bonding in Methane
HH
HH
Draw the following compounds
PCl3 H2O
SF2 AlCl3
Do NowGet out your homework to be stamped and
be prepared to answer
What is a covalent bond
What types of elements do covalent bonds form between
What are valence electrons
How many electrons are in a bond
Single Bond
Two electrons are shared between two atoms
1 electron pair
Represented by 1 line between the atoms
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Double Bond
Four electrons are shared between two atoms
2 electron pairs
Represented by 2 lines between the atoms
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Double bonds Try ItDouble bonds Try It
Draw the Lewis dot diagram for
O3
CO2
CF2S
Triple Bond
Six electrons are shared between two atoms
3 electron pairs
Represented by 3 lines between the atoms
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
10
Structures
Dot structures can be made for covalent bonds Place shared electrons between the 2 symbols
either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in cov bond Structural formulas use dashes but also
show spatial arrangement of atoms
How Covalent Bonds Form
Draw the Lewis dot diagrams for all the atoms in CH4
Draw 1 carbon diagram
Draw 4 hydrogen diagrams
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
C
Bonding in Methane
H HH
H
C
Bonding in Methane
HH
HH
Draw the following compounds
PCl3 H2O
SF2 AlCl3
Do NowGet out your homework to be stamped and
be prepared to answer
What is a covalent bond
What types of elements do covalent bonds form between
What are valence electrons
How many electrons are in a bond
Single Bond
Two electrons are shared between two atoms
1 electron pair
Represented by 1 line between the atoms
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Double Bond
Four electrons are shared between two atoms
2 electron pairs
Represented by 2 lines between the atoms
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Double bonds Try ItDouble bonds Try It
Draw the Lewis dot diagram for
O3
CO2
CF2S
Triple Bond
Six electrons are shared between two atoms
3 electron pairs
Represented by 3 lines between the atoms
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
How Covalent Bonds Form
Draw the Lewis dot diagrams for all the atoms in CH4
Draw 1 carbon diagram
Draw 4 hydrogen diagrams
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
C
Bonding in Methane
H HH
H
C
Bonding in Methane
HH
HH
Draw the following compounds
PCl3 H2O
SF2 AlCl3
Do NowGet out your homework to be stamped and
be prepared to answer
What is a covalent bond
What types of elements do covalent bonds form between
What are valence electrons
How many electrons are in a bond
Single Bond
Two electrons are shared between two atoms
1 electron pair
Represented by 1 line between the atoms
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Double Bond
Four electrons are shared between two atoms
2 electron pairs
Represented by 2 lines between the atoms
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Double bonds Try ItDouble bonds Try It
Draw the Lewis dot diagram for
O3
CO2
CF2S
Triple Bond
Six electrons are shared between two atoms
3 electron pairs
Represented by 3 lines between the atoms
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
C
Bonding in Methane
H HH
H
C
Bonding in Methane
HH
HH
Draw the following compounds
PCl3 H2O
SF2 AlCl3
Do NowGet out your homework to be stamped and
be prepared to answer
What is a covalent bond
What types of elements do covalent bonds form between
What are valence electrons
How many electrons are in a bond
Single Bond
Two electrons are shared between two atoms
1 electron pair
Represented by 1 line between the atoms
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Double Bond
Four electrons are shared between two atoms
2 electron pairs
Represented by 2 lines between the atoms
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Double bonds Try ItDouble bonds Try It
Draw the Lewis dot diagram for
O3
CO2
CF2S
Triple Bond
Six electrons are shared between two atoms
3 electron pairs
Represented by 3 lines between the atoms
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
C
Bonding in Methane
H HH
H
C
Bonding in Methane
HH
HH
Draw the following compounds
PCl3 H2O
SF2 AlCl3
Do NowGet out your homework to be stamped and
be prepared to answer
What is a covalent bond
What types of elements do covalent bonds form between
What are valence electrons
How many electrons are in a bond
Single Bond
Two electrons are shared between two atoms
1 electron pair
Represented by 1 line between the atoms
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Double Bond
Four electrons are shared between two atoms
2 electron pairs
Represented by 2 lines between the atoms
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Double bonds Try ItDouble bonds Try It
Draw the Lewis dot diagram for
O3
CO2
CF2S
Triple Bond
Six electrons are shared between two atoms
3 electron pairs
Represented by 3 lines between the atoms
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
CH
Bonding in Methane
H H H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
C
Bonding in Methane
H HH
H
C
Bonding in Methane
HH
HH
Draw the following compounds
PCl3 H2O
SF2 AlCl3
Do NowGet out your homework to be stamped and
be prepared to answer
What is a covalent bond
What types of elements do covalent bonds form between
What are valence electrons
How many electrons are in a bond
Single Bond
Two electrons are shared between two atoms
1 electron pair
Represented by 1 line between the atoms
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Double Bond
Four electrons are shared between two atoms
2 electron pairs
Represented by 2 lines between the atoms
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Double bonds Try ItDouble bonds Try It
Draw the Lewis dot diagram for
O3
CO2
CF2S
Triple Bond
Six electrons are shared between two atoms
3 electron pairs
Represented by 3 lines between the atoms
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
C
Bonding in Methane
H HH
H
C
Bonding in Methane
HH
HH
Draw the following compounds
PCl3 H2O
SF2 AlCl3
Do NowGet out your homework to be stamped and
be prepared to answer
What is a covalent bond
What types of elements do covalent bonds form between
What are valence electrons
How many electrons are in a bond
Single Bond
Two electrons are shared between two atoms
1 electron pair
Represented by 1 line between the atoms
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Double Bond
Four electrons are shared between two atoms
2 electron pairs
Represented by 2 lines between the atoms
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Double bonds Try ItDouble bonds Try It
Draw the Lewis dot diagram for
O3
CO2
CF2S
Triple Bond
Six electrons are shared between two atoms
3 electron pairs
Represented by 3 lines between the atoms
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
C
Bonding in Methane
H HH
H
C
Bonding in Methane
HH
HH
Draw the following compounds
PCl3 H2O
SF2 AlCl3
Do NowGet out your homework to be stamped and
be prepared to answer
What is a covalent bond
What types of elements do covalent bonds form between
What are valence electrons
How many electrons are in a bond
Single Bond
Two electrons are shared between two atoms
1 electron pair
Represented by 1 line between the atoms
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Double Bond
Four electrons are shared between two atoms
2 electron pairs
Represented by 2 lines between the atoms
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Double bonds Try ItDouble bonds Try It
Draw the Lewis dot diagram for
O3
CO2
CF2S
Triple Bond
Six electrons are shared between two atoms
3 electron pairs
Represented by 3 lines between the atoms
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
CH
Bonding in Methane
H H
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
C
Bonding in Methane
H HH
H
C
Bonding in Methane
HH
HH
Draw the following compounds
PCl3 H2O
SF2 AlCl3
Do NowGet out your homework to be stamped and
be prepared to answer
What is a covalent bond
What types of elements do covalent bonds form between
What are valence electrons
How many electrons are in a bond
Single Bond
Two electrons are shared between two atoms
1 electron pair
Represented by 1 line between the atoms
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Double Bond
Four electrons are shared between two atoms
2 electron pairs
Represented by 2 lines between the atoms
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Double bonds Try ItDouble bonds Try It
Draw the Lewis dot diagram for
O3
CO2
CF2S
Triple Bond
Six electrons are shared between two atoms
3 electron pairs
Represented by 3 lines between the atoms
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
C
Bonding in Methane
H HH
H
C
Bonding in Methane
HH
HH
Draw the following compounds
PCl3 H2O
SF2 AlCl3
Do NowGet out your homework to be stamped and
be prepared to answer
What is a covalent bond
What types of elements do covalent bonds form between
What are valence electrons
How many electrons are in a bond
Single Bond
Two electrons are shared between two atoms
1 electron pair
Represented by 1 line between the atoms
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Double Bond
Four electrons are shared between two atoms
2 electron pairs
Represented by 2 lines between the atoms
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Double bonds Try ItDouble bonds Try It
Draw the Lewis dot diagram for
O3
CO2
CF2S
Triple Bond
Six electrons are shared between two atoms
3 electron pairs
Represented by 3 lines between the atoms
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
C
Bonding in Methane
H HH
H
C
Bonding in Methane
HH
HH
Draw the following compounds
PCl3 H2O
SF2 AlCl3
Do NowGet out your homework to be stamped and
be prepared to answer
What is a covalent bond
What types of elements do covalent bonds form between
What are valence electrons
How many electrons are in a bond
Single Bond
Two electrons are shared between two atoms
1 electron pair
Represented by 1 line between the atoms
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Double Bond
Four electrons are shared between two atoms
2 electron pairs
Represented by 2 lines between the atoms
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Double bonds Try ItDouble bonds Try It
Draw the Lewis dot diagram for
O3
CO2
CF2S
Triple Bond
Six electrons are shared between two atoms
3 electron pairs
Represented by 3 lines between the atoms
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
CH
Bonding in Methane
HH
H
CH
Bonding in Methane
HH
H
C
Bonding in Methane
H HH
H
C
Bonding in Methane
HH
HH
Draw the following compounds
PCl3 H2O
SF2 AlCl3
Do NowGet out your homework to be stamped and
be prepared to answer
What is a covalent bond
What types of elements do covalent bonds form between
What are valence electrons
How many electrons are in a bond
Single Bond
Two electrons are shared between two atoms
1 electron pair
Represented by 1 line between the atoms
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Double Bond
Four electrons are shared between two atoms
2 electron pairs
Represented by 2 lines between the atoms
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Double bonds Try ItDouble bonds Try It
Draw the Lewis dot diagram for
O3
CO2
CF2S
Triple Bond
Six electrons are shared between two atoms
3 electron pairs
Represented by 3 lines between the atoms
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
CH
Bonding in Methane
HH
H
C
Bonding in Methane
H HH
H
C
Bonding in Methane
HH
HH
Draw the following compounds
PCl3 H2O
SF2 AlCl3
Do NowGet out your homework to be stamped and
be prepared to answer
What is a covalent bond
What types of elements do covalent bonds form between
What are valence electrons
How many electrons are in a bond
Single Bond
Two electrons are shared between two atoms
1 electron pair
Represented by 1 line between the atoms
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Double Bond
Four electrons are shared between two atoms
2 electron pairs
Represented by 2 lines between the atoms
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Double bonds Try ItDouble bonds Try It
Draw the Lewis dot diagram for
O3
CO2
CF2S
Triple Bond
Six electrons are shared between two atoms
3 electron pairs
Represented by 3 lines between the atoms
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
C
Bonding in Methane
H HH
H
C
Bonding in Methane
HH
HH
Draw the following compounds
PCl3 H2O
SF2 AlCl3
Do NowGet out your homework to be stamped and
be prepared to answer
What is a covalent bond
What types of elements do covalent bonds form between
What are valence electrons
How many electrons are in a bond
Single Bond
Two electrons are shared between two atoms
1 electron pair
Represented by 1 line between the atoms
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Double Bond
Four electrons are shared between two atoms
2 electron pairs
Represented by 2 lines between the atoms
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Double bonds Try ItDouble bonds Try It
Draw the Lewis dot diagram for
O3
CO2
CF2S
Triple Bond
Six electrons are shared between two atoms
3 electron pairs
Represented by 3 lines between the atoms
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
C
Bonding in Methane
HH
HH
Draw the following compounds
PCl3 H2O
SF2 AlCl3
Do NowGet out your homework to be stamped and
be prepared to answer
What is a covalent bond
What types of elements do covalent bonds form between
What are valence electrons
How many electrons are in a bond
Single Bond
Two electrons are shared between two atoms
1 electron pair
Represented by 1 line between the atoms
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Double Bond
Four electrons are shared between two atoms
2 electron pairs
Represented by 2 lines between the atoms
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Double bonds Try ItDouble bonds Try It
Draw the Lewis dot diagram for
O3
CO2
CF2S
Triple Bond
Six electrons are shared between two atoms
3 electron pairs
Represented by 3 lines between the atoms
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
Draw the following compounds
PCl3 H2O
SF2 AlCl3
Do NowGet out your homework to be stamped and
be prepared to answer
What is a covalent bond
What types of elements do covalent bonds form between
What are valence electrons
How many electrons are in a bond
Single Bond
Two electrons are shared between two atoms
1 electron pair
Represented by 1 line between the atoms
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Double Bond
Four electrons are shared between two atoms
2 electron pairs
Represented by 2 lines between the atoms
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Double bonds Try ItDouble bonds Try It
Draw the Lewis dot diagram for
O3
CO2
CF2S
Triple Bond
Six electrons are shared between two atoms
3 electron pairs
Represented by 3 lines between the atoms
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
Do NowGet out your homework to be stamped and
be prepared to answer
What is a covalent bond
What types of elements do covalent bonds form between
What are valence electrons
How many electrons are in a bond
Single Bond
Two electrons are shared between two atoms
1 electron pair
Represented by 1 line between the atoms
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Double Bond
Four electrons are shared between two atoms
2 electron pairs
Represented by 2 lines between the atoms
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Double bonds Try ItDouble bonds Try It
Draw the Lewis dot diagram for
O3
CO2
CF2S
Triple Bond
Six electrons are shared between two atoms
3 electron pairs
Represented by 3 lines between the atoms
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
Single Bond
Two electrons are shared between two atoms
1 electron pair
Represented by 1 line between the atoms
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Double Bond
Four electrons are shared between two atoms
2 electron pairs
Represented by 2 lines between the atoms
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Double bonds Try ItDouble bonds Try It
Draw the Lewis dot diagram for
O3
CO2
CF2S
Triple Bond
Six electrons are shared between two atoms
3 electron pairs
Represented by 3 lines between the atoms
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Double Bond
Four electrons are shared between two atoms
2 electron pairs
Represented by 2 lines between the atoms
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Double bonds Try ItDouble bonds Try It
Draw the Lewis dot diagram for
O3
CO2
CF2S
Triple Bond
Six electrons are shared between two atoms
3 electron pairs
Represented by 3 lines between the atoms
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
Letrsquos Make FLetrsquos Make F22
FF
Letrsquos Make FLetrsquos Make F22
FF
Double Bond
Four electrons are shared between two atoms
2 electron pairs
Represented by 2 lines between the atoms
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Double bonds Try ItDouble bonds Try It
Draw the Lewis dot diagram for
O3
CO2
CF2S
Triple Bond
Six electrons are shared between two atoms
3 electron pairs
Represented by 3 lines between the atoms
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
Letrsquos Make FLetrsquos Make F22
FF
Double Bond
Four electrons are shared between two atoms
2 electron pairs
Represented by 2 lines between the atoms
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Double bonds Try ItDouble bonds Try It
Draw the Lewis dot diagram for
O3
CO2
CF2S
Triple Bond
Six electrons are shared between two atoms
3 electron pairs
Represented by 3 lines between the atoms
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
Double Bond
Four electrons are shared between two atoms
2 electron pairs
Represented by 2 lines between the atoms
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Double bonds Try ItDouble bonds Try It
Draw the Lewis dot diagram for
O3
CO2
CF2S
Triple Bond
Six electrons are shared between two atoms
3 electron pairs
Represented by 3 lines between the atoms
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Double bonds Try ItDouble bonds Try It
Draw the Lewis dot diagram for
O3
CO2
CF2S
Triple Bond
Six electrons are shared between two atoms
3 electron pairs
Represented by 3 lines between the atoms
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Double bonds Try ItDouble bonds Try It
Draw the Lewis dot diagram for
O3
CO2
CF2S
Triple Bond
Six electrons are shared between two atoms
3 electron pairs
Represented by 3 lines between the atoms
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
Letrsquos Make O2
OO
Letrsquos Make O2
OO
Double bonds Try ItDouble bonds Try It
Draw the Lewis dot diagram for
O3
CO2
CF2S
Triple Bond
Six electrons are shared between two atoms
3 electron pairs
Represented by 3 lines between the atoms
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
Letrsquos Make O2
OO
Double bonds Try ItDouble bonds Try It
Draw the Lewis dot diagram for
O3
CO2
CF2S
Triple Bond
Six electrons are shared between two atoms
3 electron pairs
Represented by 3 lines between the atoms
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
Double bonds Try ItDouble bonds Try It
Draw the Lewis dot diagram for
O3
CO2
CF2S
Triple Bond
Six electrons are shared between two atoms
3 electron pairs
Represented by 3 lines between the atoms
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
Triple Bond
Six electrons are shared between two atoms
3 electron pairs
Represented by 3 lines between the atoms
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
Letrsquos Make N2
NN
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
Letrsquos Make N2
Letrsquos Make N2
NN
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
Letrsquos Make N2
NN
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
Triple bonds Try ItTriple bonds Try It
Draw the Lewis Dot Diagram for
HCN
N2O
C2H2
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
Lewis Structures summaryLewis Structures summary Place shared electrons between the 2
symbols either as pair of dots or dashes Ex H-H or Ouml=Ouml or NequivN
Each dash represents a single covalent bond Unshared pairs lone pairs non-bonding
pairs = valence e- pairs not in covalent bond
Structural formulas use dashes but also show spatial arrangement of atoms Oriented to maximize distance between e-
pairs (bonded or unshared)43
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
44
Polyatomic ions
Even though overall charged polyatomic ions are covalently bonded together
Overall charge comes from extra electrons either gained or lost in order to achieve an octet for all constituent atoms
Ex SO32-
O S O O
Use brackets to denote total charge
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
Polyatomic IonsPolyatomic Ions
Covalently bonded With additional or removed electrons
Cations lose and anions gain in e- count
NO31- SO3
2-
PO43- CN1-
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum Polyatomic ion
Divide Determine
Always ____ never ____________ _______ ldquobullyrdquoMake Complete
Except Give
Not enough pairs Ionic compound bc ____________ is central
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
Making SenseMaking Sense
General Steps to Lewis StructuresGeneral Steps to Lewis Structures
Sum total val e-Polyatomic ion Add e- if anion or Subtract e- if cation
Divide by 2 for of pairsDetermine central atom
Always Carbon never ldquoone armrdquo elements least ldquobullyrdquoMake single bondsComplete octet on external atoms
Except HydrogenGive left over pairs to the central atom for octet
Not enough pairs Make double or triple bondsIonic compound bc metal is central No octet needed
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
48
Resonance structures
Occur when possible to draw two or more valid electron dot structures for a molecule Originally thought that electrons would flip back and
forth (resonate) between the options Actual bonding is a hybrid (mixture) of the options All valid structures are separated by double headed
arrow Ex O3 (ozone)
Ouml = Ouml ndash Ouml harr Ouml - Ouml = Ouml
˙˙ ˙˙
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
49
Exceptions to Octet Rule If total of valence e- for compound is odd the
octet rule cannot be satisfied Nitrogen dioxide
Phosphorus pentachloride
Sulfur hexafluoride
Boron trifluoride readily reacts with NH3
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
50
VSEPR Theory
Valence-shell electron-pair repulsion theory States the repulsion between electron pairs
cause molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible
Non-bonding pairs are important because they will repel the other e- pairs more No other atom stakes claim therefore held closer to
the central nucleus and will squeeze out the others
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
51
Common Molecular shapes
bonds (σ) lone pairs Shape Bond lt s
2 0 Linear 180
2 2 Bent 105
3 0 Trigonal planar 120
3 1 Pyramidal 107
3 2 T shaped 90180
4 0 tetrahedral 1095
4 2 Square planar 90180
5 0 Trigonal bipyramidal 12090
6 0 octahedral 90
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
52
httpwwwchempurdueedugchelpvseprrule3ex2html
SciLink VSEPR Rules
Draw the Lewis structure for the molecule or ion Count the total number of regions of high electron
density (bonding and unshared electron pairs) around the central atom Double and triple bonds count as ONE REGION OF HIGH
ELECTRON DENSITY An unpaired electron counts as ONE REGION OF HIGH
ELECTRON DENSITY For molecules or ions that have resonance structures you
may use any one of the resonance structures Examples Test My Knowledge
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
53
VSPER rules continued
Identify the most stable arrangement of the regions of high electron density as ONE of the molecular shapes Examples
Determine the positions of the atoms based on the types of electron pairs present (ie bonding pairs vs unshared pairs)
Identify the molecular structure based on the positions of the ATOMS (NOT on the regions of high electron density)
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
54
Letrsquos try
Practice CO2 BF3
Linear triatomic (180) trigonal planar (120) H2O CH4
bent triatomic (105) tetrahedral (1095) NH3 PCl5
Pyramid (107) trigonal bipyramidal (90120) SF6 XeF4
Octahedral (90) square planar (90180) ClF3
T-shaped (90180)
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
55
84 Polar Bonds and Molecules
Think back to electronegativityhellip The amount of pull one atom has over the shared electrons in a
bond (please consult new table with values) If the electronegativity values are the same or really close
(ex two identical atoms) then the bond is said to be non-polar covalent because they are sharing the electrons equally
However if the atoms are sharing unequally due to one atom having a higher electronegativity value the bonds are said to be polar covalent The more electronegative atom pulls the electrons closer to its
own nucleus thus forming an uneven electron cloud
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
56
Bond Types
Table 83 on page 238 describes the bond types based upon electronegativity value differences 00-04 non-polar covalent 04-20 polar covalent 20-40 ionic bond
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
57
ldquoSlightrdquo charges
The more electronegative atom has a slightly negative (δ-) charge
The less electronegative atom has a slightly positive (δ+) charge The slight charge is denoted by the lower case
Greek letter delta (δ) above the element symbol An arrow with a vertical line (+rarr) points away
from the δ+ atom towards the δ- atom above the bond dash to show the e- movement in a bond
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
58
Polar Molecules A molecule can only be polar if its constituent bonds
are polar A symmetrical molecule with polar bonds is non-
polar since the bonds will negate each other If not symmetrical there will be a general δ+ and δ-
region to the molecule A polar molecule with 2 polar regions is called a
dipole Use your table of electronegativity to decide if each
of your molecular geometry practice compounds have polar or non-polar bonds and if they are polar or non-polar molecules
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
Ionic bonds
If electronegativity difference is greater than 20 the bond is ionic Metal + Nonmetal
Cation + Anion
59
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
60
Cations
Atom becomes positively charged particle Name is identical to the element + ion Ex Na Na+ + 1e-
ldquoSodiumrdquo ionized to ldquosodium ionrdquo or ldquosodium cationrdquo Properties are drastically different
Main group metals form cations with charge equal to group number for noble-gas configs
Transition metals can only achieve lsquopseudo noble-gas electron configurationsrsquo
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
61
Anions
Non-metal atoms gain electrons to become negatively charged
Value equals American group number - 8 Name usually has ndashide suffix
Ex chlorine + e- chloride Ions have noble-gas electron configurations
of noble gas in same period
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
62
72 Ionic bonds amp compounds
Compounds are comprised of cations and anions Usually metal cation and non-metal anion
Unless made with polyatomic ions (quizzes ) Electrically neutral
MUST be balanced Held together by electrostatic forces
Called ionic bonds Like north and south magnets
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
63
Chemical Formula
Uses element symbols and subscripts Symbol of elements in compound Subscript is number of each in compound
Ionic compounds use ldquoformula unitsrdquo =lowest whole-number ratio of ions in a neutral
compound Ex Sodium sulfide
Na2S (2 Na1+ needed to balance 1S2-)
Unlike sugar because in repeating crystal structure
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
64
Properties
Crystalline solids at room temperature Table salt
High melting points Conduct electric current when melted or
dissolved in water Batteries Faucet water
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
Na Cl
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
Na Cl
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
Can you have 2 bonds
Letrsquos make BeCl2
Be ClCl
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
Can it make 2 bonds
Letrsquos make BeCl2
Be ClCl
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
Letrsquos make Mg(OH)2
OMgO
H H
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
Letrsquos make Mg(OH)2
OMgO
H H
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
O
H
Letrsquos make Mg(OH)2
Mg O
H
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
72
73 Bonding in Metals
Metallic bond Attraction of free floating valence electrons with
close packed metal cations Valence electrons = sea of electrons
Free floating and mobile Allows for conductivity ductility and malleability
Able to shift and rearrange both cations and electrons
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
73
Crystalline structure
Metal cations arrange in very compact and orderly patterns Body-centered
8 neighbors Na K Fe W Cr
Face- centered 12 neighbors
Au Ag Al Pb Cu Hexagonal close-packed
12 neighbors Cd Zn Mg
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces
74
Alloys
Mixtures of 2 or more elementsndash at least 1 is a metal
Important for properties superior to those of component elements Substitutional
Similar sized element fits into crystal pattern Brass Zn partakes in Cu atomic crystal
Interstitial Smaller sized atom fits into nooks (interstices) or
spaces formed within crystal structure Steel C fits into Fe spaces