The Foundations of Chemistry

260 CHAPTER 6: Chemical Periodicity

Metal Nonmetal

Oxide 
Oxide 88n Salt

calcium oxide

sulfur trioxide CaO(s) SO 3 (
) 88nCaSO 4 (s) calcium sulfate

magnesium oxide

carbon dioxide MgO(s) CO 2 (g) 88nMgCO 3 (s) magnesium carbonate

sodium oxide

tetraphosphorus decoxide 6Na 2 O(s)P 4 O 10 (s) 88n4Na 3 PO 4 (s) sodium phosphate

 2

 2

 1

 6

 4

 5

 2

 2

 1

 6

 4

 5

EXAMPLE 6-8 Acidic Character of Oxides

Arrange the following oxides in order of increasing molecular (acidic) character: SO 3 , Cl 2 O 7 ,

CaO, and PbO 2.

Plan

Molecular (acidic) character of oxides increases as nonmetallic character of the element that is

combined with oxygen increases (see Figure 6-8).

increasing nonmetallic character

888888888888888888888888n

CaPb S  Cl

Periodic group: IIA IVA VIA VIIA

Solution

increasing molecular character

888888888888888888888888n

Thus, the order is CaOPbO 2 SO 3 Cl 2 O 7

EXAMPLE 6-9 Basic Character of Oxides

Arrange the oxides in Example 6-8 in order of increasing basicity.

Plan

The greater the molecular character of an oxide, the more acidic it is. Thus, the most basic

oxides have the least molecular (most ionic) character (see Figure 6-8).

Solution

increasing basic character

8888888888888888888n

molecular Cl 2 O 7 SO 3 PbO 2 CaO ionic

EXAMPLE 6-10 Predicting Reaction Products

Predict the products of the following pairs of reactants. Write a balanced equation for each

reaction.

(a) Cl 2 O 7 (
)H 2 O(
)88n

Reactions of Metal Oxides with Nonmetal Oxides

Another common kind of reaction of oxides is the combination of metal oxides (basic anhy-

drides) with nonmetal oxides (acid anhydrides), with no change in oxidation states, to form salts.