Phosphorus ($\mathrm{P}$, $Z=15$)

The chemical element with atomic number fifteen.

A form of elemental phosphorus distinct from molecular white phosphorus.

A molecular allotrope consisting of tetrahedral ${\mathrm{P}}_4$ molecules. Every vertex has three P–P bonds and one lone pair; its $60^{\circ }$ P–P–P angles produce substantial angle strain.