Phosphorus oxoacid

Some of them are unstable and have not been isolated, but the derived anions and organic groups are present in stable salts and esters.

The most important ones—in biology, geology, industry, and chemical research—are the phosphoric acids, whose esters and salts are the phosphates.

In general, any hydrogen atom bonded to an oxygen atom is acidic, meaning that the –OH group can lose a proton H+ leaving a negatively charged –O− group and thus turning the acid into a phosphorus oxoanion.

Two or more of these PO4 tetrahedra may be connected by shared single-bonded oxygens, forming linear or branched chains, cycles, or more complex structures.

These acids, and their esters and salts ("phosphates") include some of the best-known and most important compounds of phosphorus.