Question

KF has ccp structure. How many $F^{-}$ ions and octahedral voids are there in this unit cell respectively?

• A. 4 and 4
• B. 4 and 8
• C. 8 and 4
• D. 6 and 6

Answer 1

The correct option is A 4 and 4

In $KF$, FCC structure, the anions occupy corners and face atom which contributes $6\times \left(1/2\right)+8\times \left(1/8\right)=4$ atoms.

Since the charge must be balanced, there must be 4 $K^{+}$ atoms that occupy octahedral voids.

So $F^{-}$ ions and octahedral voids are $4,4.$

Hence, the correct option is $A$