The Foundations of Chemistry

Notice that H 2 N 2 O 2 has a 11 ratio of
nitrogen to oxygen, as would the
hypothetical HNO.

166 CHAPTER 4: Some Types of Chemical Reactions

Ternary acids that have one fewer O atom than the “-ous” acids (two fewer O atoms

than the “-ic” acids) are named using the prefix “hypo-” and the suffix “-ous.” These are

acids in which the oxidation state of the central nonmetal is lower by 2than that of the

central nonmetal in the “-ous acids.”

Formula Ox. No. Name

HClO 
 1 hypochlorousacid

H 3 PO 2 
 1 hypophosphorousacid

HIO 
 1 hypoiodousacid

H 2 N 2 O 2 
 1 hyponitrousacid

Acids containing one more oxygen atomper central nonmetal atom than the normal

“-ic acid” are named “perstemic” acids.

Formula Ox. No. Name

HClO 4 
 7 perchloricacid

HBrO 4 
 7 perbromicacid

HIO 4 
 7 periodicacid

The oxoacids of chlorine can be summarized as follows:

Formula Ox. No. Name

HClO 
 1 hypochlorousacid

HClO 2 
 3 chlorousacid

HClO 3 
 5 chloricacid

HClO 4 
 7 perchloricacid

Ternary saltsare compounds that result from replacing the hydrogen in a ternary acid

with another ion. They usually contain metal cations or the ammonium ion. As with binary

compounds, the cation is named first. The name of the anion is based on the name of the

ternary acid from which it is derived.

An anion derived from a ternary acid with an “-ic” ending is named by dropping the

“-ic acid” and replacing it with “-ate.” An anion derived from an “-ous acid” is named by

replacing the suffix “-ous acid” with “-ite.” The “per-” and “hypo-” prefixes are retained.

Formula Name

(NH 4 ) 2 SO 4 ammonium sulfate (SO 42 , from sulfuric acid, H 2 SO 4 )

KNO 3 potassium nitrate (NO 3 , from nitric acid, HNO 3 )

Ca(NO 2 ) 2 calcium nitrite (NO 2 , from nitrous acid, HNO 2 )

LiClO 4 lithium perchlorate (ClO 4 , from perchloric acid, HClO 4 )

FePO 4 iron(III) phosphate (PO 43 , from phosphoric acid, H 3 PO 4 )

NaClO sodium hypochlorite (ClO, from hypochlorous acid, HClO)

Acidic salts contain anions derived from ternary polyprotic acids in which one or more

acidic hydrogen atoms remain. These salts are named as if they were the usual type of

ternary salt, with the word “hydrogen” or “dihydrogen” inserted after the name of the

cation to show the number of acidic hydrogen atoms.