Question

A cation is in the centre touches three anions. Assume that the anions also touch each other. The limiting radius ratio, $r^{+}/r^{-}$ is

• A. $0.1547$
• B. $0.4141$
• C. $0.7322$
• D. $0.2252$

Answer 1

Answer: (A)

$\frac{r^{+}+r^{-}}{r^{-}}=\frac{2}{\sqrt{3}}$
$\frac{r+}{r+}+1=\frac{2}{\sqrt{3}}$
$\frac{r+}{r-}+1=1.1547$
$\frac{r+}{r-}=0.1547$