Petrucci • Harwood • Herring • Madura
GENERAL
CHEMISTRY
Ninth
Edition
Principles and Modern Applications
Chapter 10: Chemical Bonding I:
Basic Concepts
Philip Dutton
University of Windsor, Canada
Prentice-Hall © 2007
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General Chemistry: Chapter 10
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Contents
10-1
10-2
10-3
10-4
10-5
10-6
10-7
10-8
10-9
Lewis Theory: An Overview
Covalent Bonding: An Introduction
Polar Covalent Bonds
Writing Lewis Structures
Resonance
Exceptions to the Octet Rule
The Shapes of Molecules
Bond Order and Bond Lengths
Bond Energies
 Focus On Molecules in Space: Measuring Bond Lengths
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General Chemistry: Chapter 10
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10-1 Lewis Theory: An Overview
 Valence e- play a
fundamental role in
chemical bonding.
 e- transfer leads to
ionic bonds.
 Sharing of e- leads to
covalent bonds.
 e- are transferred of
shared to give each atom
a noble gas configuration
 the octet.
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General Chemistry: Chapter 10
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Lewis Symbols
A chemical symbol represents the nucleus
and the core e-.
Dots around the symbol represent valence e-.
•
• Si •
•
• Al •
•
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• As •
•
P•
•
••
• Se
•
•
••
••
• Bi •
•
• Sb •
•
••
I
••
•
General Chemistry: Chapter 10
••
Ar
••
•
••
••
•N•
•
••
••
••
••
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EXAMPLE 10-2
Writing Lewis Structures of Ionic Compounds. Write Lewis
structures for the following compounds: (a) BaO; (b) MgCl2 ;
(c) aluminum oxide.
• O•
••
2+ ••
Ba
O
••
2-
••
Ba•
••
••
BaO
•
Note the use of the ―fishhook‖ arrow to denote a
single electron movement. A ―double headed‖
arrow means that two electrons move.
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General Chemistry: Chapter 10
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EXAMPLE 10-2
••
••
2+
Mg
••
2 Cl
••
-
••
• Cl
••
••
••
Mg •
••
MgCl2
•
• Cl
••
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General Chemistry: Chapter 10
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10-2 Covalent Bonding: An Introduction
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General Chemistry: Chapter 10
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Coordinate Covalent Bonds
+
H
Cl
H N H
H
••
Cl
••
-
••
••
H N
H
••
H
H
Note the ―double headed‖ arrow
showing that two electrons move.
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General Chemistry: Chapter 10
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Multiple Covalent Bonds
•O
••
• C•
•
••
•
•
•
••
•
••
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••
••
O C O
•
•
•
••
•
••
O C O
••
••
O•
•
••
••
••
••
••
•
••
•
O C O
General Chemistry: Chapter 10
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Multiple Covalent Bonds
•
•
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••
••
N N
•
•
•
•
••
N N
N N
General Chemistry: Chapter 10
••
••
•
••
•N
•
N•
••
•
••
•
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Paramagnetism of Oxygen
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General Chemistry: Chapter 10
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10-3 Polar Covalent Bonds and
Electrostatic Potential Maps
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General Chemistry: Chapter 10
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Polar Molecules
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General Chemistry: Chapter 10
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Electronegativity
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General Chemistry: Chapter 10
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Percent Ionic Character
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General Chemistry: Chapter 10
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10-4 Writing Lewis Structures
All the valence e- of atoms must appear.
Usually, the e- are paired.
Usually, each atom requires an octet.
 H only requires 2 e-.
Multiple bonds may be needed.
 Readily formed by C, N, O, S, and P.
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General Chemistry: Chapter 10
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Skeletal Structure
Identify central and terminal atoms.
H
H C
H
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H
C O H
H
General Chemistry: Chapter 10
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Skeletal Structure
 Hydrogen atoms are always terminal atoms.
 Central atoms are generally those with the lowest
electronegativity.
 Carbon atoms are always central atoms.
 Generally structures are compact and symmetrical.
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General Chemistry: Chapter 10
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Strategy for
Writing Lewis
Structures
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General Chemistry: Chapter 10
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EXAMPLE10-7
Writing a Lewis Structure for a Polyatomic Ion. Write the
Lewis structure for the nitronium ion, NO2+.
Step 1:
Total valence e- = 5 + 6 + 6 – 1 = 16 e-
Step 2:
Identify the central and terminal atoms
Step 3:
Plausible structure:
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to terminal atoms:
General Chemistry: Chapter 10
••
O—N—O
••
••
••
Add
••
••
Step 4:
e-
O—N—O
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EXAMPLE 10-7
16 – 4 – 12 = 0
Step 5:
Determine e- left over:
Step 6:
Use multiple bonds to satisfy octets.
••
••
••
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••
••
O—N—O
••
••
••
+
O=N=O
••
••
General Chemistry: Chapter 10
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Formal Charge
FC = #valence e- - #lone pair e- ••
1
2
#bond pair e-
+ ••
O=N=O
••
••
1
FC(O) = 6 - 4 –
(4) = 0
2
FC(N) = 5 - 0 –
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1
(8) = +1
2
General Chemistry: Chapter 10
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Alternative Lewis Structure
••
••
••
O—N—O
••
+
O
+
N
••
O
••
-
••
••
••
••
1
FC(O≡) = 6 - 2 –
(6) = +1
2
FC(N) = 5 - 0 –
1
(8) = +1
2
1
FC(O—) = 6 - 6 –
(2) = -1
2
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General Chemistry: Chapter 10
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Alternative Lewis Structures
 Sum of FC is the overall charge.
 FC should be as small as possible.
 Negative FC usually on most electronegative elements.
 FC of same sign on adjacent atoms is unlikely.
+
+
•• -
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••
••
O≡N—O
••
General Chemistry: Chapter 10
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EXAMPLE 10-7
Using the Formal Charge in Writing Lewis Structures. Write
the most plausible Lewis structure of nitrosyl chloride, NOCl,
one of the oxidizing agents present in aqua regia.
2+
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2-
-
2+
-
General Chemistry: Chapter 10
-
+
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10-5 Resonance
••+ •• -
-½ ••
••
O
O O
••
••
- ••
••+ ••
O
O O
••
••
••
••
••+ •• -½
O
O O
••
••
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General Chemistry: Chapter 10
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10-6 Exceptions to the Octet Rule
Odd e- species.
••
••
•
N=O
••
H
••
•
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General Chemistry: Chapter 10
O—H
••
•
H—C—H
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Exceptions to the Octet Rule
Incomplete octets.
••
••
••
F
+ F
••
••
••
B
B
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F
F
F
F
••
••
••
+
-
F
General Chemistry: Chapter 10
F
-
B
F
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Exceptions to the Octet Rule
Expanded octets.
P
Cl
F
S
P
Cl
Cl
Cl
F
F
F
F
••
Cl
••
••
Cl
F
••
Cl
••
••
Cl
••
••
••
••
••
••
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General Chemistry: Chapter 10
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Expanded Valence Shell
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General Chemistry: Chapter 10
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10-7 The Shapes of Molecules
H
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O
General Chemistry: Chapter 10
H
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Terminology
 Bond length – distance between nuclei.
 Bond angle – angle between adjacent bonds.
 VSEPR Theory
 Electron pairs repel each other whether they are in
chemical bonds (bond pairs) or unshared (lone pairs).
Electron pairs assume orientations about an atom to
minimize repulsions.
 Electron group geometry – distribution of e- pairs.
 Molecular geometry – distribution of nuclei.
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General Chemistry: Chapter 10
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Balloon Analogy
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General Chemistry: Chapter 10
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Methane, Ammonia and Water
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General Chemistry: Chapter 10
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Table 10.1 Molecular Geometry as a
Function of Electron Group Geometry
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General Chemistry: Chapter 10
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General Chemistry: Chapter 10
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General Chemistry: Chapter 10
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General Chemistry: Chapter 10
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General Chemistry: Chapter 10
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General Chemistry: Chapter 10
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Applying VSEPR Theory
 Draw a plausible Lewis structure.
 Determine the number of e- groups and identify
them as bond or lone pairs.
 Establish the e- group geometry.
 Determine the molecular geometry.
 Multiple bonds count as one group of electrons.
 More than one central atom can be handled
individually.
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General Chemistry: Chapter 10
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Dipole Moments
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General Chemistry: Chapter 10
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Dipole Moments
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General Chemistry: Chapter 10
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Bond Order and Bond Length
Bond Order
 Single bond, order = 1
 Double bond, order = 2
Bond Length
 Distance between two nuclei
Higher bond order
 Shorter bond
 Stronger bond
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General Chemistry: Chapter 10
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General Chemistry: Chapter 10
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Bond Energies
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General Chemistry: Chapter 10
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General Chemistry: Chapter 10
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EXAMPLE 10-15
Calculating an Enthalpy of Reaction from Bond Energies.
The reaction of methane (CH4) and chlorine produces a mixture
of products called chloromethanes. One of these is
monochloromethane, CH3Cl, used in the preparation of silicones.
Calculate H for the reaction.
ΔHrxn =  ΔH(product bonds) - ΔH(reactant bonds)
=  ΔH bonds formed -  ΔH bonds broken
= -770 kJ/mol – (657 kJ/mol) = -113 kJ/mol
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General Chemistry: Chapter 10
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Focus on Molecules in Space: Measuring
Bond Lengths
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General Chemistry: Chapter 10
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End of Chapter Questions
•Testing your decisions:
–If you get an error or a nonsense result, then
climb back to an intersection where you KNOW
you were correct, and take another route.
a
b
c
d?
e?!#
e
f
Answer
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General Chemistry: Chapter 10
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