Naming Inorganic Binary Compounds

A comprehensive guide to naming inorganic binary compounds including ionic compounds (Type I and II), polyatomic ions, and covalent compounds with reference tables and naming rules.

Ionic Compounds

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

Naming Rules:

  1. The cation is always named first and the anion second
  2. A cation takes its name from the element name (e.g., K⁺ is potassium)
  3. An anion is named by taking the first part of the element name and adding -ide (e.g., Br⁻ is bromide)

Monatomic Ions

CationCation NameAnionAnion Name
Al³⁺AluminiumBr⁻Bromide
Ba²⁺BariumCl⁻Chloride
Be²⁺BerylliumF⁻Fluoride
Ca²⁺CalciumH⁻Hydride
Cs⁺CesiumI⁻Iodide
H⁺HydrogenN³⁻Nitride
Li⁺LithiumO²⁻Oxide
Mg²⁺MagnesiumP³⁻Phosphide
K⁺PotassiumS²⁻Sulfide
Rb⁺Rubidium
Ag⁺Silver
Na⁺Sodium
Sr²⁺Strontium
Zn²⁺Zinc

Polyatomic Ions

Polyatomic ions contain more than one atom. For oxyanion series:

  • With 2 members: -ite for fewer O atoms, -ate for more O atoms
  • With 3+ members: hypo- prefix for fewest O atoms, per- prefix for most O atoms
IonIon NameIonIon Name
NH₄⁺AmmoniumMnO₄⁻Permanganate
C₂H₃O₂⁻AcetateNO₂⁻Nitrite
CO₃²⁻CarbonateNO₃⁻Nitrate
HCO₃⁻Hydrogen carbonate (bicarbonate)OH⁻Hydroxide
ClO⁻HypochloriteO₂²⁻Peroxide
ClO₂⁻ChloritePO₄³⁻Phosphate
ClO₃⁻ChlorateHPO₄²⁻Hydrogen phosphate
ClO₄⁻PerchlorateH₂PO₄⁻Dihydrogen phosphate
CN⁻CyanideSO₃²⁻Sulfite
CrO₄²⁻ChromateSO₄²⁻Sulfate
Cr₂O₇⁻DichromateHSO₄⁻Hydrogen sulfate (bisulfate)

Type I Binary Ionic Compounds

Type I compounds contain a metal that forms only one type of cation (e.g., Na⁺, Ca²⁺).

Naming: [Cation Name] [Anion Name]

CompoundIons PresentName
CaSCa²⁺, S²⁻Calcium sulfide
CsBrCs⁺, Br⁻Cesium bromide
Li₃NLi⁺, N³⁻Lithium nitride
MgOMg²⁺, O²⁻Magnesium oxide
KFK⁺, F⁻Potassium fluoride
AgIAg⁺, I⁻Silver iodide
NaClNa⁺, Cl⁻Sodium chloride

Type II Binary Ionic Compounds

Type II compounds contain metals that can form more than one type of cation (e.g., Fe²⁺ and Fe³⁺).

Naming: Use Roman numerals to indicate charge (e.g., iron(II) for Fe²⁺, iron(III) for Fe³⁺)

Alternate naming: -ous suffix for lower charge, -ic suffix for higher charge

IonSystematic NameAlternate 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
Hg²⁺Mercury(II)Mercuric
Sn²⁺Tin(II)Stannous
Sn⁴⁺Tin(IV)Stannic

Covalent Compounds

Covalent compounds contain two nonmetals.

Naming Rules:

  1. Name the first element using the full element name
  2. Name the second element as if it were an anion (-ide suffix)
  3. Use prefixes to denote the numbers of atoms: mono-, di-, tri-, tetra-, penta-, hexa-, hepta-, octa-
  4. Never use mono- prefix for the first element
  5. Drop the vowel from a prefix when the second element begins with a vowel (e.g., mono- + oxide = monoxide)

Naming Pattern:

[Prefix][First Nonmetal] [Prefix][Second Nonmetal]-ide

CompoundSystematic NameCommon Name
NONitrogen monoxideNitric oxide
NO₂Nitrogen dioxide
N₂ODinitrogen monoxideNitrous oxide
N₂O₃Dinitrogen trioxide
N₂O₄Dinitrogen tetroxide
N₂O₅Dinitrogen pentoxide