Question

The maximum packing efficiency of an ionic solid, $A{B}_2$ (fluorite structure) is about $\left(\frac{r_{A^{2+}}}{r_{B^{-}}}=\sqrt{3}-1\right)$

• A. $0.52$
• B. $0.76$
• C. $0.63$
• D. $0.79$

Answer 1

Answer: (C)

$P.E.=\frac{4\times \frac{4}{3}{r}_{A^{2+}}^3+8\times \frac{4}{3}\pi r_{B^{-}}^3}{{\left(\left[\frac{4}{\sqrt{3}}\left(r_{A^{2+}}+r_{B^{-}}\right)\right]\right)}^3}\approx 0.63$