Most ionic compounds contain a single anion and a single cation. For the purpose of naming the compound, it is important to be able to recognize the atom groups that are the formulae of the common polyatomic ions.
K2SO4
contains sulfate ion
NaHCO3
contains hydrogen carbonate ion
Mg(NO3)2
contains nitrate ion
CaCO3
contains carbonate ion
Note that when more than one formuia unit of the ion is present, as in Mg(NO
3)
2. the ion formula is enclosed in brackets.
The name of these has the
cation name followed by the
anion name.
CaCO3 contains
carbonate ions (CO32–) and calcium ions (Ca2+).
The name of this compound is calcium carbonate.
Mg(NO3)2 contains
magnesium ions (Mg2+) and nitrate ions (NO3–).
The name of this compound is magnesium nitrate.
Note that the name of ionic compounds does NOT indicate the relative numbers of the two ions that are present. This is because the relative numbers of the two types of ions can be deduced from their charges.