Calculate the energy $($in $e\frac{V}{?}/$atom$)$ for vacancy formation in some metal, M $,$ given that the equilibrium number of vacancies at $231C$ is

$5\mathrm{.}20{10}^{23}{m}^{-3}.$ The density and atomic weight $($at $231C)$ for this metal are $13\mathrm{.}7\frac{g}{c}{m}^3$ and $87\mathrm{.}20\frac{g}{m}ol,$ respectively.

$Q_v=$

i

eV$/$atom