Question

In sodium chloride, $C{l}^{-}$ ions form ccp arrangement. Which site will $N{a}^{+}$ ions occupy in this structure?

• A. cubic
• B. tetragonal
• C. octahedral
• D. trigonal bipyramidal

Answer 1

The correct option is C octahedral

In sodium chloride, $C{l}^{-}$ ions form ccp arrangement. $N{a}^{+}$ ions will occupy octahedral voids in this structure. It will have coordination number of $6$.

This can be confirmed from the radius ratio. For octahedral voids, the radius ratio is $\frac{r}{R}=0.414$. The radius ratio is the ratio of the radius (r) of the atom or ion which can exactly fit in the octahedral void formed by spheres of radius R.

$\frac{r}{R}=\frac{95}{181}=0.524$