Question

AB is an ionic solid. If the ratio of ionic radii of ${\text{A}}^{\text{+}}$ and ${\text{B}}^{-}$ is 0.52, what is the coordination number of ${\text{B}}^{-}$ ?

• A. 2
• B. 3
• C. 6
• D. 8

Answer 1

Answer: (C)

Radius ratio $r^{+}/r^{-}$
Coordination number
0.155-0.225
3
0.225-0.414
4
0.414-0.732
6
0.732-1.00
8
Hence, if the ratio of ionic radii is 0.52, then the coordination number of $B^{-}$ is 6.