How do you name simple ionic compounds?

1 Answer

The name of an ionic compound is
name of cation + name of anion

You have to memorize the formulas of the common ions. One you have done that, you follow these rules to generate the names.


Cations in of metals in Groups 1 and 2 have the same name as the metal (e.g., sodium or magnesium). There is one common polyatomic cation — NH₄⁺ ammonium.
Transition metals form cations with more than one charge. To the names of these ions, we add the charge as a capital Roman numeral in parentheses.
Fe²⁺ is iron(II); Fe³⁺ is iron(III); Cu⁺ is copper(I); Cu²⁺ is copper(II)
Note that there are no spaces between the letters and the parentheses.


a. Monatomic anions

The name of a monatomic anion is
stem of element name + ide
H⁻ hydride
F⁻ fluoride
O²⁻ oxide
S²⁻ sulfide
N³⁻ nitride
P³⁻ phosphide

b. Naming Oxyanions

Oxyanions are polyatomic anions that contain oxygen. When an element forms two oxyanions, the one with less oxygen is given a name ending in -ite and the one with more oxygen is given a name that ends in -ate.
NO₂⁻ nitrite
NO₃⁻ nitrate
SO₃²⁻ sulfite
SO₄²⁻ sulfate

The halogens can form four oxyanions. In this case, the two in the middle use the -ite and -ate suffixes. The one with the fewest oxygen atoms adds the prefix hypo-, and the one with the most oxygen gets the prefix per-.
ClO⁻ hypochlorite
ClO₂⁻ chlorite
ClO₃⁻ chlorate
ClO₄⁻ perchlorate

Some polyatomic oxyanions also contain one or two hydrogen atoms. We name these ions by adding the word hydrogen or dihydrogen in front of the name of the anion.
HCO₃⁻ hydrogen carbonate
HSO₄⁻ hydrogen sulfate
HPO₄²⁻ hydrogen phosphate
H₂PO₄⁻ dihydrogen phosphate

Here are some examples of ionic compounds and their names.
MgO = Mg²⁺ + O²⁻ magnesium oxide
FeS = Fe²⁺ + S²⁻ iron(II) sulfide
LiH = Li⁺ +H⁻ lithium hydride
H₂S = H⁺ + S²⁻ hydrogen sulfide
NaOH = Na⁺ + OH⁻ sodium hydroxide
CaCO₃ = Ca²⁺ + CO₃²⁻ calcium carbonate
FeSO₄ = Fe²⁺ + SO₄²⁻ iron(II) sulfate
FeSO₃ = Fe²⁺ + SO₃²⁻ iron(II) sulfite
(NH₄)₃PO₄ = NH₄⁺ + PO₄³⁻ ammonium phosphate
Mg(HCO₃)₂ = Mg²⁺ + HCO₃⁻ magnesium hydrogen carbonate