106
Formulas and Nomenclature
acid there must be one negative charge left on the residue. For example, if HBr
loses its H
+ , the Br~ has a minus-one charge; if H 2 SO 4 loses its two H
+ , the
SOj" has a minus-two charge, and so on. The names and formulas of acids that
you should know in this course are listed in two separate groups below, because
the traditional method of naming them depends on whether or not the molecule
contains oxygen.
Acids That Do Not Contain Oxygen
These acids are named by putting the prefix hydro- before the rest of the name
of the characteristic element (or elements) and adding the suffix -ic.
HF
hydrofluoric acid
HCN
hydrocyanic acid
HC1
hydrochloric acid
H 2 S
hydrosulfuric acid
HBr
hydrobromic acid
HN 3
hydrazoic acid
HI
hydriodic acid
Acids That Contain Oxygen
If the characteristic element forms only one oxygen acid, the name is that of the
characteristic element followed by the suffix -ic. Thus H 2 CO :i is carbonic acid.
If the characteristic element forms two oxygen acids, the name of the one with
the larger number of oxygen atoms ends in-/c, and the name of the one with the
smaller number of oxygen atoms ends in -ous. Thus HNO :! is nitric acid, and
HNO 2 is nitrous acid.
If there are several oxygen acids, there is a systematic terminology to indicate more or less oxygen atoms than the number assigned to the acid whose
name ends in -ic. This can be illustrated by the oxygen acids of chlorine:
HC1O 4
perchloric acid
one more oxygen than the -ic acid
HClO 3
chloric acid
arbitrarily given the -ic ending
HClO 2
chlorous acid
one less oxygen than the -ic acid
HC1O
hypochlorous acid
one less oxygen than the -ous acid
Table 8-3 includes the common acids that contain oxygen.
The prefix thio- indicates that sulfur is present, usually as a replacement for
one or more oxygen atoms in a compound whose name is familiar. For example,
in thiosulfuric acid, one O atom of sulfuric acid has been replaced by an S atom;
in thiocyanic acid, the only O atom of cyanic acid has been replaced; in thioarsenic acid, all of the O atoms of arsenic acid have been replaced by S. The rules
of naming do not normally show how many O atoms are replaced. HSCN is
placed in Table 8-3 because of the many similarities between oxygen and sulfur.
Formulas and Nomenclature
acid there must be one negative charge left on the residue. For example, if HBr
loses its H
+ , the Br~ has a minus-one charge; if H 2 SO 4 loses its two H
+ , the
SOj" has a minus-two charge, and so on. The names and formulas of acids that
you should know in this course are listed in two separate groups below, because
the traditional method of naming them depends on whether or not the molecule
contains oxygen.
Acids That Do Not Contain Oxygen
These acids are named by putting the prefix hydro- before the rest of the name
of the characteristic element (or elements) and adding the suffix -ic.
HF
hydrofluoric acid
HCN
hydrocyanic acid
HC1
hydrochloric acid
H 2 S
hydrosulfuric acid
HBr
hydrobromic acid
HN 3
hydrazoic acid
HI
hydriodic acid
Acids That Contain Oxygen
If the characteristic element forms only one oxygen acid, the name is that of the
characteristic element followed by the suffix -ic. Thus H 2 CO :i is carbonic acid.
If the characteristic element forms two oxygen acids, the name of the one with
the larger number of oxygen atoms ends in-/c, and the name of the one with the
smaller number of oxygen atoms ends in -ous. Thus HNO :! is nitric acid, and
HNO 2 is nitrous acid.
If there are several oxygen acids, there is a systematic terminology to indicate more or less oxygen atoms than the number assigned to the acid whose
name ends in -ic. This can be illustrated by the oxygen acids of chlorine:
HC1O 4
perchloric acid
one more oxygen than the -ic acid
HClO 3
chloric acid
arbitrarily given the -ic ending
HClO 2
chlorous acid
one less oxygen than the -ic acid
HC1O
hypochlorous acid
one less oxygen than the -ous acid
Table 8-3 includes the common acids that contain oxygen.
The prefix thio- indicates that sulfur is present, usually as a replacement for
one or more oxygen atoms in a compound whose name is familiar. For example,
in thiosulfuric acid, one O atom of sulfuric acid has been replaced by an S atom;
in thiocyanic acid, the only O atom of cyanic acid has been replaced; in thioarsenic acid, all of the O atoms of arsenic acid have been replaced by S. The rules
of naming do not normally show how many O atoms are replaced. HSCN is
placed in Table 8-3 because of the many similarities between oxygen and sulfur.