Question

Two ions $A^+$ and $B^-$ have radii 104 and 200 pm respectively, in a cubic close packed crystal of compound AB. The co-ordination no. of A is

• A. 4
• B. 8
• C. 6
• D. 3

Answer 1

Answer: (C)

6

Answer 2

Radius ratio= $\frac{r_+}{r_-} = \frac{104 \, pm}{200 \, pm} = 0.52$ As it lies in the range 0.414 - 0.732, the coordination number will be 6