Chemistry Reference
In-Depth Information
negative charges. They are called oxoanions but were formerly known as oxyan-
ions. For the seven most important oxoanions, the name is that of the root of the
central element with the ending -
ate
added. They are listed in the third column
of Table 6.3. Once we have learned the names and formulas of these ions, we
can deduce the formulas of the corresponding ions with fewer or more oxygen
atoms. Ions ending in -
ite
have one fewer oxygen atom than the corresponding
-
ate
ions. In four cases, removal of two oxygen atoms from an ion ending in -
ate
results in an ion named with the prefix
hypo
- and the ending -
ite
. For three ions
that end with -
ate,
addition of one oxygen atom yields an ion named with the
prefix
per
- and the ending -
ate
. Note in Table 6.3 that all the ions with a given
central atom have the same charge. Note also that the charge on each third
through fifth period oxoanion is equal to the classical group number minus 8,
just as for the monatomic anions, but the charge on each
second
period oxoan-
ion has
two fewer
negative charges
Oxoanions of even group
elements have even charges
( ) and those of odd group
elements have odd charges
(
2
1
r
3
).
(CO
3
2
, NO
3
NO
2
).
,
and
See Figure 5.13.
EXAMPLE 6.12
Br
, BrO
3
, BrO
2
, BrO
,
BrO
4
.
Name
and
Solution
The names are bromide ion, bromate ion, bromite ion, hypobromite ion, and
perbromate ion.
Practice Problem 6.12
Write the formula for (a) iodite ion and
(b) hypoiodite ion.
EXAMPLE 6.13
What are the formulas for (a) sulfate ion and (b) carbonate ion?
Solution
SO
4
2
CO
3
2
.
The formulas are (a)
and (b)
Practice Problem 6.13
Write the formula for each of the follow-
ing ions:
(a) Sulfite ion
(b) Chlorate ion
(c) Nitrate ion
(d) Nitrite ion
SPECIAL ANIONS
Other important anions that don't fit into the prior two categories are called spe-
cial anions in this topic. They are listed in Table 6.4. Names for anions that con-
tain oxygen but are not included in Table 6.3 may sometimes be determined
because of a periodic relationship between their central element and that of an
ion in that table. For example, is analogous to because both cen-
tral elements are in periodic groups numbered VII. Its name is permanganate,
MnO
4
ClO
4
