Naming Inorganic Binary Compounds

Rules for naming inorganic ionic and covalent types of chemical compounds.

Ionic compounds

Binary ionic compounds contain a positiv ion (cation) and a negative ion (anion). The cation is a metal in most cases, and is always written first in the formula. The anion is a nonmetal in most cases.

In the naming, these rules must be followed:

The cation is always named first and the anion second.
A cation takes its name from the name of the element. Example: K⁺ is called potassium in the names of compounds containing this ion.
An anion is named by taking the first part of the element name and adding -ide. Example: the Br^- ion is called bromide.

A monatomic ion is an ion consisting of a single atom. Examples are given in the table:

Naming Inorganic Binary Compounds
Monatomic Cations and Anions
Cation	Name	Anion	Name
Al³⁺	Aluminium	Br^-	Bromide
Ba²⁺	Barium	Cl^-	Chloride
Be²⁺	Beryllium	F^-	Fluoride
Ca²⁺	Calcium	H^-	Hydride
Cs⁺	Cesium	I^-	Iodide
H⁺	Hydrogen	N^3-	Nitride
Li⁺	Lithium	O^2-	Oxide
Mg²⁺	Magnesium	P^3-	Phosphide
K⁺	Potassium	S^2-	Sulfide
Rb⁺	Rubidium
Ag⁺	Silver
Na⁺	Sodium
Sr²⁺	Strontium
Zn²⁺	Zinc

A polyatomic ion contains more than one atom, these atoms can be of the same element or of different elements.

There are polyatomic anion series with one given element together with different numbers of oxygen atoms, called oxyanions:

In oxyanion series with two members, the name of the one with the smaller number of oxygen atoms ends in -ite.
The name of the one with the larger number ends in -ate.
When more than two oxyanions make up a series,

hypo- (less than) are used as prefix to name the member of the series with the fewest oxygen atoms.
per- (more than) are used as prefix to name the member of the series with the most oxygen atoms.

Naming Inorganic Binary Compounds
Polyatomic Ions
Ion	Name	Ion	Name
NH₄⁺	Ammonium	MnO4-	Permanganate
C₂H₃O₂^-	Acetate	NO₂^-	Nitrite
CO₃^2-	Carbonate	NO₃^-	Nitrate
HCO₃^-	Hydrogen carbonate (or bicarbonate)	OH^-	Hydroxide
ClO^-	Hypochlorite	O₂^2-	Peroxide
ClO₂^-	Chlorite	PO₄^3-	Phosphate
ClO₃^-	Chlorate	HPO₄^2-	Hydrogen phosphate
ClO₄^-	Perchlorate	H₂PO₄^2-	Dihydrogen phosphate
CN^-	Cyanide	SO₃^2-	Sulfite
CrO₄^2-	Chromate	SO₄^2-	Sulfate
Cr₂O₇^-	Dichromate	HSO₄^-	Hydrogen sulfate (or bisulfate)

Type I binary ionic compounds contains a metal that forms only one type of cation. Examples: Na⁺ and Ca²⁺. Examples of naming of compounds type I is given in the table:

Naming Inorganic Binary Compounds
Type I Compounds, Naming Examples
Compound	Ions present	Name
CaS	Ca²⁺, S^2-	Calcium sulfide
CsBr	Cs⁺, Br^-	Cesium bromide
Li3N	Li⁺, N^3-	Lithium nitride
MgO	Mg²⁺, O^2-	Magnesium oxide
KF	K⁺, F^-	Potassium fluoride
AgI	Ag⁺, I^-	Silver iodide
NaCl	Na⁺, Cl^-	Sodium chloride

Type II binary ionic compounds can form more than one type of cation. Examples: Fe²⁺ and Fe³⁺, Pb²⁺ and Pb⁴⁺.

For type II compounds the charge of the metal ion must be specified, and this is systematically done with Roman numeral indication.

Example: iron(II) for Fe²⁺ and iron(III) for Fe³⁺. Then, the compounds with formula FeCl₂ and FeCl₃ are called iron(II) chloride and iron(III) chloride, respectively.

An older way to separate between metal ions that forms two different charges:

The ion with the lower charge has a name ending in -ous and the one with the higher charge has a name ending in -ic.

Naming Inorganic Binary Compounds
Type II Cations
Ion	Systematic name	Alternate name
Co²⁺	Cobalt(II)	Cobaltous
Co³⁺	Cobalt(III)	Cobaltic
Cu⁺	Copper(I)	Cuprous
Cu²⁺	Copper(II)	Cupric
Fe²⁺	Iron(II)	Ferrous
Fe³⁺	Iron(III)	Ferric
Pb²⁺	Lead(II)	Plumbous
Pb⁴⁺	Lead(IV)	Plumbic
Hg⁺	Mercury(I)	Mercurous
Hg2²⁺*	Mercury(II)	Mercuric
Sn²⁺	Tin(II)	Stannous
Sn⁴⁺	Tin(IV)	Stannic

Covalent compounds (contain two nonmetals)

Rules for naming binary covalent compounds:

Nonmetal X + Nonmetal Y + "-ide"

The first element in the formula is named first, using the full element name
The second element is named as if it were an anion.
Prefixes are used to denote the numbers of atoms present (mono-, di-, tri-, tetra-, penta-, hexa-, hepta-, octa-)
The prefix mono- is never used for naming the first element. Example: CO is called carbon monoxide (not monocarbon monoxide).
Some elements beginning with vowels (Oxygen, for example) replace the vowel ending -o or -a of its prefix; mono- + Oxide = Monoxide, O₄ = Tetroxide, O₅ = Pentoxide, and so on.

Naming Inorganic Binary Compounds
Examples of Naming Covalent Compounds with Nitrogen and Oxygen
Compound	Systematic name	Common name
NO	Nitrogen monoxide	Nitric oxide
NO₂	Nitrogen dioxide
N₂O	Dinitrogen monoxide	Nitrous oxide
N₂O₃	Dinitrogen trioxide
N₂O₄	Dinitrogen tetroxide
N₂O₅	Dinitrogen pentoxide