text: From the commercial perspective, the most important phosphite salt is basic lead phosphite. Many salts containing the phosphite ion have been investigated structurally, these include sodium phosphite pentahydrate (NaHPO·5HO). (NH)HPO·HO, CuHPO·HO, SnHPO and Al(HPO)·4HO. The structure of  is approximately tetrahedral.
   has a number of canonical resonance forms making it isoelectronic with bisulfite ion, , which has a similar structure.