Chemistry - Solid State Question with Solution | TestHub

In face centred cubic, packing efficiency

$=\frac{\text{Volume occupied by 4 atoms in the unit cell}\times 100}{\text{Volume of the unit cell}}$

$=\frac{4\times \left(4/3\right)\mathrm{\pi r}{}^3\times 100}{{\left(2\sqrt{2}\mathrm{r}\right)}^3}=\frac{\left(16/3\right)\mathrm{\pi r}{}^3\times 100}{16\sqrt{2}\mathrm{r}{}^3}=74\text{\%}$