Chemistry - Solid State Question with Solution | TestHub

$\mathrm{C}{\mathrm{l}}^{-}$ions form ccp lattice i.e 8 at corners + 6 at face centres.

$\Rightarrow 8\times \frac{8}{18}+6\times \frac{1}{2}=4\mathrm{ }\mathrm{C}{\mathrm{l}}^{-}\mathrm{ }\mathrm{i}\mathrm{o}\mathrm{n}\mathrm{s}$

$\mathrm{N}{\mathrm{a}}^{+}$at octahedral voids 12 at centre edges plus one at body centre.

$\Rightarrow 12\times \frac{1}{4}+1=4\mathrm{N}{\mathrm{a}}^{+}\mathrm{ }\mathrm{i}\mathrm{o}\mathrm{n}\mathrm{s}$

i.e$\text{4NaCl}$molecules per unit cell.