Question

What are the coordination numbers $(C.N.)$ of $C{a}^{2+}$ and $F^{-}$ ion in calcium fluoride $(Ca{F}_2)$ crystal structure ?

• A. $C.N$ . of $C{a}^{2+}=4$ and $F=8$
• B. $C.N$ . of $C{a}^{2+}=6$ and $F^{-}=6$
• C. $C.N$ . of $C{a}^{2+}=8$ and $F^{-}=8$
• D. $C.N$ . of $C{a}^{2+}=8$ and $F^{-}=4$

Answer 1

Answer: (D)

Each $C{a}^{2+}$ ion is surrounded by $8F^{-}$ ions and each $F^{-}$ ion by $4C{a}^{2+}$ ions. Thus, coordination number of $C{a}^{2+}$ is $8$ and $F^{-}$ is $4$