The Foundations of Chemistry

WW

e know a great deal about the molecular structures of many thousands of

compounds, all based on reliable experiments. In our discussion of theories

of covalent bonding, we must keep in mind that the theories represent an

attempt to explain and organize experimental observations.For bonding theories to be valid,

they must be consistent with the large body of experimental observations about molec-

OUTLINE

8-1 A Preview of the Chapter

8-2 Valence Shell Electron Pair

Repulsion (VSEPR) Theory

8-3 Polar Molecules: The Influence

of Molecular Geometry

8-4 Valence Bond (VB) Theory

Molecular Shapes and Bonding

8-5 Linear Electronic Geometry:

AB 2 Species (No Lone Pairs

of Electrons on A)

8-6 Trigonal Planar Electronic

Geometry: AB 3 Species (No

Lone Pairs of Electrons on A)

8-7 Tetrahedral Electronic

Geometry: AB 4 Species (No

Lone Pairs of Electrons on A)

8-8 Tetrahedral Electronic

Geometry: AB 3 U Species (One

Lone Pair of Electrons on A)

8-9 Tetrahedral Electronic

Geometry: AB 2 U 2 Species (Two

Lone Pairs of Electrons on A)

8-10 Tetrahedral Electronic

Geometry: ABU 3 Species

(Three Lone Pairs of Electrons

on A)

8-11 Trigonal Bipyramidal Electronic

Geometry: AB 5 , AB 4 U, AB 3 U 2 ,

and AB 2 U 3

8-12 Octahedral Electronic

Geometry: AB 6 , AB 5 U, and

AB 4 U 2

8-13 Compounds Containing Double

Bonds

8-14 Compounds Containing Triple

Bonds

8-15 A Summary of Electronic and

Molecular Geometries

OBJECTIVES

After you have studied this chapter, you should be able to

• Describe the basic ideas of the valence shell electron pair repulsion (VSEPR) theory


• Use the VSEPR theory to predict the electronic geometry of polyatomic molecules and
  ions


• Use the VSEPR theory to predict the molecular geometry of polyatomic molecules and
  ions


• Describe the relationships between molecular shapes and molecular polarities


• Predict whether a molecule is polar or nonpolar


• Describe the basic ideas of the valence bond (VB) theory


• Analyze the hybrid orbitals used in bonding in polyatomic molecules and ions


• Use hybrid orbitals to describe the bonding in double and triple bonds

A computer model of a polar
molecule of wood alcohol, or

methanol, CH 3 OH (C, gray;
H, white; O, red). The ball-and-

stick model is shown inside a
computer-generated molecular

surface. The surface is color-coded to
show how charge ranges from very

positive (red)to very negative
(blue).