Question

Which is not the correct statement for ionic solids in which positive and negative ions are held by strong electrostatic attractive forces?

• A. The radius ratio $r^{+}/r^{-}$ increases as coordination number increases
• B. As the difference in size of ions increases coordination number increases
• C. When coordination number is eight, the $r^{+}/r^{-}$ ratio lies between $0.225$ to $0.414$
• D. In ionic solid of the type $AX$ ($ZnS$, Wurtzite) the coordination number of ${Zn}^{2+}$ and $S^{2-}$ respectively are $4$ and $4$

Answer 1

The correct option is C When coordination number is eight, the $r^{+}/r^{-}$ ratio lies between $0.225$ to $0.414$

A) Radius ratio increases from 0.155-1 as coordination no. increases.

B) The difference in the size of ions increases as coordination number increases that is why in the CsCl structure having high coordination no. of 8, the size of the cation and anion is almost similar.

C) When radius ratio lies between $0.225$ to $0.414$ then coordination number is $4$. Coordination no. is 8 when the radius ration is 0.732-1.

D) Statement is correct.

Option C is the correct answer.