6.0 Introduction
6.4 Valence Bond Theory and Hybridization
6.1 Molecular Shapes
6.5 Molecular Orbital Theor
y and Delocalized Bon
ds
6.2 Central Atoms with Expanded Valence
Shells
6.6 Chapter Summary and Objectives
6.3 Larger Molecules
6.7 Exercises
Chapter 6 Molecular Structure & Bonding
6.0
INTRODUCTION
A molecule is characterized by its three-dime
nsional structure, which is the arrangement
of its nuclei. The positions of the nuclei
are determined by the lengths of the bonds
between them and the angles at which those bon
ds intersect. A molecular structure plays a
key role in determining both the physical a
nd chemical properties of the molecule. The
positions, strengths, and polarities of the bonds
influence a molecule's reactivity. Size and
shape are primary factors in governing the ce
llular processes in which biomolecules, like
proteins and DNA, participate. The structure of
a molecule dictates whether it is a solid,
liquid, or gas at a given set of conditions.
In this chapter, we apply increasingly sophisticated models to the study of structure
and bonding. We first use the valence-shell
electron-pair repulsion model (electrostatic
arguments) to describe the arrangements of
electron groups around an atom. Then we
explain how and why bonds are formed w
ith valence bond theory. We conclude the
chapter with a brief introduction into molecular orbital theory to explain shortcomings in the valence bond theory and to introduce
the electronic structure of molecules.
THE OBJECTIVES OF CHAPTER 6 ARE TO: •
explain the VSEPR (
valence-
shell
electron-
pair r
epulsion) model and demonstrate how to use
it to predict the geometry of the electron regions around a central atom;
(^) •
show how to extend the VSEPR model to larger molecules;
(^) •
describe valence bond theory;
(^) •
distinguish between sigma and pi bonding;
(^) •
define hybridization and show how it is used;
(^) •
use molecular orbital theory to explain delocalized bonding; and
(^) •
infer the structure and bonding in a
molecule from its Lewis structure.
Chapter 6 Molecular Structure & Bonding
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State
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