Chemical Nomenclature

The following summarizes the distinguishing features of different kinds of formulas and names.

Binary Covalent Compounds

General Formula

AaBb

For example, N2O5 or CO2  

General Name

(prefix unless mono)(name of first element in formula) (prefix)(root of second element)ide

For example, dinitrogen pentoxide or carbon dioxide

 

Binary Ionic Compounds

General Formula

MaAb

For example, NaCl or FeCl3

General Name

(name of metal) (root of nonmetal)ide

or (name of metal)(Roman #) (root of nonmetal)ide

For example, sodium chloride or iron(III) chloride

Ionic Compounds with Polyatomic Ion(s)

General Formula

MaXb or (NH4)aXb  

X = recognized formula of polyatomic ion

For example, Li2HPO4 or CuSO4 or NH4Cl or (NH4)2SO4

General Name

(name of metal) (name of polyatomic ion)

or (name of metal)(Roman #) (name of polyatomic ion)

or ammonium (root of nonmetal)ide

or ammonium (name of polyatomic ion)

For example, lithium hydrogen phosphate or copper(II) sulfate or ammonium chloride or ammonium sulfate

 

Ionic Compounds with Polyatomic Ion(s)

General Formula

MaXb or (NH4)aXb  

X = recognized formula of polyatomic ion

For example, Li2HPO4 or CuSO4 or NH4Cl or (NH4)2SO4

General Name

(name of metal) (name of polyatomic ion)

or (name of metal)(Roman #) (name of polyatomic ion)

or ammonium (root of nonmetal)ide

or ammonium (name of polyatomic ion)

For example, lithium hydrogen phosphate or copper(II) sulfate or ammonium chloride or ammonium sulfate

 

Binary Acids

General Formula

HX(aq)

For example, HCl(aq)

General Name

hydro(root)ic acid

For example, hydrochloric acid

 

Oxyacids

General Formula

HaXbOc

For example, HNO3 or H2SO4 or H3PO4

General Name

(root)ic acid

For example, nitric acid or sulfuric acid or phosphoric acid

 

The following links take you to pages that have more information about writing names and formulas for compounds.

Binary Covalent Nomenclature

Ionic Nomenclature

Cation Names and Formulas

Anion Names and Formulas

Acid Nomenclature