Calcium monophosphide


Calcium monophosphide is the inorganic compound with the formula CaP. The term "calcium phosphide" also describes the composition Ca3P2, which is also called calcium phosphide. CaP and Ca3P2 are completely different materials. CaP is black, Ca3P2 is red-brown. The monophosphide decomposes to Ca3P2 at about 600 °C.

Structure and properties

The structures of CaP and sodium peroxide are very similar. The solid is described as a salt: 2P24−, or Ca2P2. Since the bonding is ionic, the diphosphide centers carry negative charge and are easily protonated. Upon hydrolysis this material releases diphosphine :
The hydrolyses of CaP and calcium carbide are similar, except that diphosphine spontaneously ignites in air. Thus, CaP must be protected from air.