Past exam of the chemistry B course of the University of Cambridge / 2022 / Paper 2 / B9 / a / i / Solution

P${}_4$ is a tetrahedron of four phosphorus atoms, with a P–P bond along every edge. Each P has three P–P sigma bonds and one lone pair. The P–P–P angles are $60^{\circ }$, so these are strained, bent bonds rather than four independent tetrahedral electron-pair arrangements with ideal bond angles. This molecular unit is characteristic of white phosphorus.