Calcium monophosphide

Calcium monophosphide is the inorganic compound with the formula CaP. It is sometimes also known as "calcium phosphide", which also describes a different compound with composition Ca₃P₂. Calcium monophosphide is a black solid.

Calcium monophosphide

Names
Other names Calcium phosphide
Identifiers
CAS Number	39373-03-0 Y
3D model (JSmol)	Interactive image
ECHA InfoCard	100.049.465
EC Number	254-431-6
InChI InChI=1S/2Ca.P2/c;;1-2/q2*+1;-2 Key: ZNARFUPPJCLHKN-UHFFFAOYSA-N
SMILES [Ca+2].[P-2][P-2].[Ca+2]
Properties
Chemical formula	CaP (Ca2P2)
Appearance	black solid
Solubility in water	decomposes
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H260, H300, H311, H318, H330, H400
Precautionary statements	P223, P231+P232, P260, P264, P270, P271, P273, P280, P284, P301+P310, P302+P352, P304+P340, P305+P351+P338, P310, P312, P320, P321, P322, P330, P335+P334, P361, P363, P370+P378, P391, P402+P404, P403+P233, P405, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

Structure and properties

The structures of CaP and sodium peroxide (Na₂O₂) are very similar.^[1] The solid is described as a salt: (Ca²⁺)₂P₂⁴⁻, or Ca₂P₂. Since the bonding is ionic, the diphosphide centers carry negative charge and are easily protonated. Upon hydrolysis this material releases diphosphine (P₂H₄):^[2]

Ca₂P₂ + 4 H₂O → 2 Ca(OH)₂ + P₂H₄

The hydrolyses of CaP and calcium carbide (CaC₂) are similar, except that diphosphine spontaneously ignites in air. Thus, CaP must be protected from air.

CaP decomposes to Ca₃P₂ at about 600 °C.

3 CaP → Ca₃P₂ + 1/4 P₄