Chemistry - A Molecular Science

Chapter 4 The Ionic Bond

4.0 Introduction

4.5 Polyatomic Ions

4.1 Ionic Bonding

4.6 Naming Ionic Compounds

4.2 Naming and Predicting Ions

4.7 Structure of Ionic Compounds

4.3 Relative Sizes of Ions

4.8 Chapter Summary and Objectives

4.0

INTRODUCTION

The valence electrons in metals are at relativ

ely high potential energies, so metals have

low ionization energies, while the unfilled valen

ce orbitals in nonmetals are at relatively

low potential energies, so nonmetals have high

electronegativities. Electrons seek to lower

their potential energy whenever possible, so

when metal atoms combine with nonmetal

atoms, the high-energy valence electrons of the metal are

transferred

to the low-energy

orbitals of the nonmetal. The result is that

the metal becomes a cation and the nonmetal

becomes an anion. The oppositely charged ions are held together by an electrostatic force called an

ionic bond

, and the compounds between me

tals and nonmetals are called

ionic

compounds

. Ionic compounds are not molecular becau

se each cation in an ionic solid is

surrounded by a number of anions, none of whic

h is uniquely associated with the cation.

The situation is quite different in the

bonds between two nonmetals because the energy

difference between the valence orbitals of tw

o nonmetals is relatively small. Thus, when

nonmetals bond to one another, the valence electrons are

shared

rather than transferred.

The resulting bond is known as a

covalent bond

, and compounds composed only of

nonmetals are called

covalent

• or

molecular

, as individual molecules are readily

identified. The properties of ionic and molecular substances are quite different. In this chapter, we discuss the ionic bond and ionic compounds. The covalent bond and molecular compounds will be discussed in Chapters 5 and 6.

4.4 Oxidation States

4.9 Exercises

* Although covalent compounds are not

discussed until the next chapter,

we define them here so that we c

an compare ionic compounds to them

in this chapter.

THE OBJECTIVES OF CHAPTER 4 ARE TO: •

discuss the properties of ions;

(^) •
define oxidation states and show how they are determined in ions and molecules;
(^) •
demonstrate how to name ionic compounds;
(^) •
explain how to predict the formulas of binary ionic compounds; and
(^) •
explain why ionic compounds are not molecular.
Chapter 4 The Ionic Bond
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