Question

Given: Radius of $A^{2+}$ = 100 pm; Radius of $C^{+}$ = 240 pm; Radius of $B^{2-}$ = 300 pm; Radius of $D^{-}$ = 480 pm. Which is/are correct statement?

• A. The coordination number of $A^{2+}$ in compound AB is 4.
• B. The coordination number of $A^{2+}$ in compound AB is 6.
• C. The coordination number of $C^{+}$ in compound CD is 6.
• D. The coordination number of $C^{+}$ in compound CD is 8.

Answer 1

Answer: (A), (C)

The correct options are
A The coordination number of $A^{2+}$ in compound AB is 4.
C The coordination number of $C^{+}$ in compound CD is 6.

Radius ratio = $\frac{r^{+}}{r^{-}}$
In AB, radius ratio = 0.33, the cation sits in the tetrahedral void, coordination number is 4.
In CD, radius ratio = 0.5, the cation sits in the octahedral void, coordination number is 6.