Question

In which of the following pairs, the cations occupy, same type of site?

• A. $NaCl,CsCl$
• B. Zinc blende $\left(ZnS\right),N{a}_{2}O$
• C. $N{a}_{2}O,Ca{F}_2$
• D. $CsCl,$ Zinc blende $\left(ZnS\right)$

Answer 1

The correct option is B Zinc blende $\left(ZnS\right),N{a}_{2}O$

Both Zinc blende $\left(ZnS\right)$ and $N{a}_{2}O$ crystalize in ccp structure.
In Zinc blende,
$S^{2-}$ ions forms the fcc lattice. Thus, it occupies the corners and face centre of the cubic unit cell.
$Z{n}^{2+}$ occupies the 4 alternate tetrahedral voids. The coordination number of Zinc blende is 4:4

In $N{a}_{2}O,$ oxide ions form the ccp lattice and sodium ions occupying tetrahedral voids with coordination number of 4:8.
$Z{n}^{2+}\text{and}N{a}^{+}$ possess same coordination number and occupy the same tetrahedral sites.

In $CsCl$ and $CsBr$, the cation occupies the cubical void.
In $Ca{F}_2,C{a}^{2+}$ form the ccp lattice.
In $NaCl,N{a}^{+}$ occupies all the octahedral voids.

Thus, the correct option is (d).