Polyatomic ion

Polyatomic ion

A polyatomic ion is an ion consisting of multiple atoms associated together by covalent bonds which can be considered as acting as a single unit in the context of acid/base chemistry or in the formation of salts. Note that in this context, a polyatomic ion is also referred to as a radical.

Some commonly-occurring polyatomic ions and their charges are indicated below

 carbonate    CO₃^2-

 bicarbonate  HCO₃^-

 nitrate      NO₃^-

 phosphate    PO₄^3-

 sulfate      SO₄^2-

 acetate      CH₃C(=O)O^-

 ammonium     NH₄⁺

 hydroxide    OH^-

 pyridinium[?]   C₅H₅NH⁺

The atoms of a polyatomic ion are always associated with each other via covalent or coordinate-covalent bonds.

A polyatomic ion that is primarily associated with other atoms by covalent, rather than ionic, forces might more properly be referred to as a functional group.