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
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
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
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