Oxyanion

An oxyanion or oxoanion is a chemical compound with the generic formula A_xO_yz− (where A represents a chemical element and O represents an oxygen atom). Oxoanions are formed by a large majority of the chemical elements. The formulae of simple oxoanions are determined by the octet rule. The structures of condensed oxoanions can be rationalized in terms of AO_n polyhedral units with sharing of corners or edges between polyhedra. The phosphate and polyphosphate esters AMP, ADP and ATP are important in biology.