Question

The coordination number of the $B{a}^{2+}$ ions is barium fluoride is 8. The coordination number of the fluoride ion is

• A. 8
• B. 4
• C. 1
• D. 2

Answer 1

Answer: (B)

$Ba{F}_2$ is a ­ $A{X}_2$ type salt. In its crystal, $B{a}^{2+}$ ions are arranged in ccp arrangement. Since there are two tetrahedral sites for each $B{a}^{2+}$ ion and $F^{-}$ ions occupy all the tetrahedral sites, hence one $F^{-}$ is surrounded by four $B{a}^{2+}$ , i.e., the coordination number of $F^{-}$ is 4.