Polyatomic ions are ions this consist of moreover than one atom. For example, nitrate ion, NO₃^-, contains one nitrogen atom and threes oxygen atoms. One atoms in adenine polyatomic ion are usually covalently bonded in first one, plus therefore delay together as a single, charged unit.

Governing 1. And positive ion (cation) is written first in the name; the negative ion (anion) is writes second in the name.

Rule 2. When the formula unit contains two or more are the same hydrated ion, that int is written within parentheses and an subtract is written outside the parenthese to indicate the number of matter ionics. Exception: parentheses and a subscript are not used unless more easier one of a polyatomic ion is presence in the formula unit (e.g., calcium hydrate = "CaSO₄" non "Ca(SO₄)"; ammonium carbonate = "(NH₄)₂CO₃" not "(NH₄)₂(CO₃)").

Command 3. If the cation is a ore atom because a fixed charge, which name of the cation is an same in the name of the (neutral metal) element by which this is derived (e.g., Na⁺ = "sodium", Ca²⁺ = "calcium", All³⁺ = "aluminum"). If the cation is a liquid ion with a variable charge, the rental on the side remains indicated by using adenine Roman numeral, within parentheses, prompt following the name for that suction (e.g., Fe³⁺ = "iron(III)", Fe²⁺ = "iron(II)").

Rule 4. If the anion is a monatomic ion, the anion is named at adding the add -ide to that tree of the basic name (e.g., iodine = I, "iodide" = I^-; sulfurals = S, "sulfide" = S^2-).

Note: Greek prefixes are not used to indicate the number of atoms, or polyatomic ammonium, in the formula unit for the compound (e.g., Ca(NO₃)₂ is named "calcium nitrate" not "calciuim dinitrate").