Ch. 6 & 7 - Covalent BondingCh. 6 & 7 - Covalent Bonding

Molecular or Covalent CompoundsMolecular or Covalent Compounds

(p. 164 – 17(p. 164 – 1755, 211 – 213), 211 – 213)

Sharing Valence ElectronsSharing Valence Electrons

Nonmetals OnlyNonmetals Only

MoleculesMolecules

Water moleculeH2O

Oxygen molecule,O2

Sucrose molecule,C12H22O11

Molecular NomenclatureMolecular Nomenclature

Prefix System Prefix System (binary compounds)(binary compounds)

1.1. Less eLess e--neg atom neg atom comes first. comes first.

2.2. Add prefixes to indicate # of atoms. Omit Add prefixes to indicate # of atoms. Omit mono- prefix on first element.mono- prefix on first element.

3.3. Change the ending of the Change the ending of the second element to -ide.second element to -ide.

PREFIXPREFIXmono-mono-

di-di-

tri-tri-

tetra-tetra-

penta-penta-

hexa-hexa-

hepta-hepta-

octa-octa-

nona-nona-

deca-deca-

NUMBERNUMBER11

22

33

44

55

66

77

88

99

1010

Molecular NomenclatureMolecular Nomenclature

Name TheseName These

NN22OO

NONO22

ClCl22OO77

CBrCBr44

COCO22

BaClBaCl22

Write formulas for theseWrite formulas for these

diphosphorus pentoxidediphosphorus pentoxidetetraiodine nonoxidetetraiodine nonoxidesulfur hexaflouridesulfur hexaflouridenitrogen trioxidenitrogen trioxideCarbon tetrahydrideCarbon tetrahydridephosphorus trifluoridephosphorus trifluoridealuminum chloridealuminum chlorideh.w. p. 235 # 10,11 h.w. p. 235 # 10,11

The TerminologyThe Terminology

The smallest entity of a covalent compound is called a ___________.

A bond is formed when one pair of electrons is shared.

Some elements,( nitrogen, carbon, and oxygen) can share more than one pair of electrons and form

bonds.

The TerminologyThe Terminology

A bond is produced when two pairs of electrons are shared.A bond is produced when three pairs of electrons are shared.Covalent bonding can also occur between two atoms of the same nonmetal. This forms a molecule.

N O F

Cl

Br

I

H

Diatomic ElementsDiatomic Elements

There are seven diatomic elements:There are seven diatomic elements:

HH22 N N22 O O22 F F22 Cl Cl2 2 Br Br2 2 I I22

Lewis StructuresLewis Structures

Octet RuleOctet Rule

– Most atoms form bonds in order to obtain 8 valence eMost atoms form bonds in order to obtain 8 valence e --

– Full energy level stability ~ Noble GasesFull energy level stability ~ Noble Gases

Ne

Lewis StructuresLewis Structures

Electron dot notations that Electron dot notations that represent compounds.represent compounds.Pairs of dots represent shared Pairs of dots represent shared electrons between bonded atomselectrons between bonded atomsAnd unshared pairs or lone pairs And unshared pairs or lone pairs that belong exclusively to one that belong exclusively to one atomatom

Drawing Lewis StructuresDrawing Lewis Structures

Determine the type and number of Determine the type and number of atoms in the molecule.atoms in the molecule.

Write the electron dot notation for Write the electron dot notation for each atom.each atom.

Determine the total number of Determine the total number of valence electrons in the atomsvalence electrons in the atoms

Drawing Lewis StructuresDrawing Lewis Structures

Arrange the atoms to form a skeleton Arrange the atoms to form a skeleton structure for the molecule. If carbon is structure for the molecule. If carbon is present, it is central - otherwise the present, it is central - otherwise the least electronegative element is least electronegative element is central. (hydrogen is never central) central. (hydrogen is never central) Then connect the atoms by electron Then connect the atoms by electron pair bonds.pair bonds.

Drawing Lewis StructuresDrawing Lewis Structures

Add lone pairs so that hydrogen has Add lone pairs so that hydrogen has a duet and each other nonmetal has a duet and each other nonmetal has an octetan octet

Count the electrons to be sure that Count the electrons to be sure that the number of valence electrons used the number of valence electrons used is equal to the number available.is equal to the number available.

Drawing Lewis StructuresDrawing Lewis Structuressingle bondssingle bonds

CFCF441 C × 4e1 C × 4e-- = 4e = 4e--

4 F × 7e4 F × 7e-- = = 28e28e--

32e32e--

FF C F

F

Each wants an octet:Each wants an octet:1 C × 8e1 C × 8e-- = 8e = 8e--

4 F × 8e4 F × 8e-- = = 32e32e--

40e40e--

-32e-32e--

must share must share 8e8e--

Practice Single BondsPractice Single Bonds

CHCH33II

HH22

FF22

HH22OO

HClHCl

NHNH33

HH22SS

CHCH44

H.W. p. 197 # 39

Drawing Lewis StructuresDrawing Lewis Structuresmultiple bondsmultiple bonds

Multiple bonds between nitrogen, carbon, and oxygen are possible

Drawing Lewis DiagramsDrawing Lewis Diagramsmultiple bondsmultiple bonds

COCO221 C × 4e1 C × 4e-- = 4e = 4e--

2 O × 6e2 O × 6e-- = = 12e12e--

16e16e--

O C OEach wants an octet:Each wants an octet:

1 C × 8e1 C × 8e-- = 8e = 8e--

2 O × 8e2 O × 8e-- = = 16e16e--

24e24e--

-16e-16e--

must share must share 8e8e--

Practice Multiple BondsPractice Multiple Bonds

CC22HH22

CHCH22OO

HCNHCN

CHCH44

CClCCl44

h.w. p. 197 #41

Polyatomic Ions ( are held together Polyatomic Ions ( are held together by covalent bonds)by covalent bonds)

To find total # of valence eTo find total # of valence e--::

– Add 1eAdd 1e-- for each negative charge. for each negative charge.

– Subtract 1eSubtract 1e-- for each positive charge. for each positive charge.

Place brackets around the ion and label the Place brackets around the ion and label the charge.charge.

Polyatomic IonsPolyatomic IonsClOClO44

--

1 Cl × 7e1 Cl × 7e-- = 7e = 7e--

4 O × 6e4 O × 6e-- = = 24e24e--

31e31e

OO Cl O

O

+ 1e+ 1e--

32e32e--

Each wants an octet:Each wants an octet:1 Cl × 8e1 Cl × 8e-- = 8e = 8e--

4 O × 8e4 O × 8e-- = = 32e32e--

40e40e--

-32e-32e--

must share must share 8e8e--

NHNH44++

1 N × 5e1 N × 5e-- = 5e = 5e--

4 H × 1e4 H × 1e-- = = 4e4e--

9e9e--

HH N H

H

- 1e- 1e--

8e8e--

44 H × 2e H × 2e-- = 8e = 8e--

1 N × 8e1 N × 8e-- = = 8e8e--

16e16e--

- 8e- 8e--

must share must share 8e8e--

Polyatomic IonsPolyatomic Ions

Practice Polyatomic IonsPractice Polyatomic Ions

PhosphatePhosphate

SulfateSulfate

NitrateNitrate

ChlorateChlorate

ChloriteChlorite

HypochloriteHypochlorite

h.w. p. 197 #42

Resonance StructuresResonance Structures

Molecules that can’t be correctly Molecules that can’t be correctly represented by a single Lewis diagram.represented by a single Lewis diagram.

Actual structure is an average of all the Actual structure is an average of all the possibilities.possibilities.

Show possible structures separated by a Show possible structures separated by a double-headed arrow.double-headed arrow.

AcidsAcids

AcidsAcids

– Compounds that form HCompounds that form H++ in water. in water.

– Formulas usually begin with ‘H’.Formulas usually begin with ‘H’.

Examples:Examples:

– HCl – hydrochloric acidHCl – hydrochloric acid

– HNOHNO33 – nitric acid – nitric acid

– HH22SOSO44 – sulfuric acid – sulfuric acid

Naming Binary acidsNaming Binary acids

Includes hydrogen and another nonmetalIncludes hydrogen and another nonmetal

use the prefix hydro- and change -ide to -use the prefix hydro- and change -ide to -ic acidic acid

HCl - hydrogen ion and chloride ionHCl - hydrogen ion and chloride ion

hydrochloric acidhydrochloric acid

HH22S hydrogen ion and sulfide ionS hydrogen ion and sulfide ion

hydrosulfuric acidhydrosulfuric acid

Naming OxyacidsNaming Oxyacids

Includes hydrogen and a polyatomic ion Includes hydrogen and a polyatomic ion containing oxygencontaining oxygenDo not include hydro- in the name.Do not include hydro- in the name.If the polyatomic ion ends in -ate, change If the polyatomic ion ends in -ate, change it to -ic acidit to -ic acidHNOHNO33 - Hydrogen and nitrate ions - Hydrogen and nitrate ionsNitric acidNitric acidIf the polyatomic ion ends in -ite, If the polyatomic ion ends in -ite, change it to -ous acidchange it to -ous acidHNOHNO22 Hydrogen and nitrite ions Hydrogen and nitrite ionsNitrous acidNitrous acid

Acid NomenclatureAcid Nomenclature

h yd ro - p re fix-ic en d in g

2 e lem en ts

-a te en d in gb ecom es-ic en d in g

-ite en d in gb ecom es

-o u s en d in g

n o h yd ro - p re fix

3 e lem en ts

AC ID Ss ta rt w ith 'H '

oxyacidsbinary acids

Name these acidsName these acids

HFHF

HH33PP

HH22SOSO44

HH22SOSO33

HCNHCN

HH22CrOCrO44

Writing Formulas Binary AcidsWriting Formulas Binary Acids

hydro- nonmetal root-ic acidhydro- nonmetal root-ic acid

Will include hydrogen and a nonmetalWill include hydrogen and a nonmetal

Criss-cross to make the charges cancel Criss-cross to make the charges cancel out. (the charge on the other element out. (the charge on the other element becomes the subscript for hydrogen)becomes the subscript for hydrogen)

Ex. Hydrochloric acidEx. Hydrochloric acid

Hydrogen and chlorideHydrogen and chloride HClHCl

Writing Formulas OxyacidsWriting Formulas Oxyacids

If acid end in –ic, then polyatomic ion If acid end in –ic, then polyatomic ion ends in –ate.ends in –ate.

If acid end in –ous, then polyatomic ion If acid end in –ous, then polyatomic ion ends in –ite.ends in –ite.

Criss-cross to make the charges cancel Criss-cross to make the charges cancel out. (the charge on the polyatomic ion out. (the charge on the polyatomic ion becomes the subscript for hydrogen)becomes the subscript for hydrogen)

Ex. Iodic acidEx. Iodic acid

hydrogen and iodatehydrogen and iodate HIOHIO33

Write formulas for theseWrite formulas for these

hydrobromic acidhydrobromic acidhydrofluoric acidhydrofluoric acidphosphoric acidphosphoric acidbromic acidbromic acidHypochlorous acidHypochlorous acidhydroiodic acidhydroiodic acidacetic acidacetic acidcarbonic acidcarbonic acidphosphorous acidphosphorous acidOxalic acidOxalic acid

h.w. p. 235 #14,15h.w. p. 235 #14,15

Bell RingerBell Ringer

p. 235 # 12