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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