Question

The coordination number of cation and anion in flourite $Ca{F}_2$ and anti-flourite $N{a}_{2}O$ are respectively:

• A. $8:4$ and $6:3$
• B. $6:3$ and $4:4$
• C. $8:4$ and $4:8$
• D. $4:8$ and $8:4$

Answer 1

The correct option is C $8:4$ and $4:8$

In case of $Ca{F}_2$, the $C{a}^{2+}$ ions are present in FCC manner and the $F^{-}$ ions are present at the tetrahedral sites. So, the coordination number of $C{a}^{2+}$ is $8$ and of $F^{-}$ is $4$.
In case of $N{a}_{2}O$, the $O^{2-}$ ions are present in FCC manner and the $N{a}^{+}$ ions are present at the tetrahedral sites. So, the coordination number of $N{a}^{+}$ is $4$ and of $O^{2-}$ is $8$.