A metaphosphate ion is an oxyanion that has the empirical formula PO3−. The structure of a metaphosphate ion can be described as being made up of PO4 structural units in which each unit shares two corners with another unit. This can come about in two ways.
- Formation of a ring, as in trimetaphosphate, illustrated.
- Formation of an infinite chain, with the same structure as in ammonium metavanadate