Question

A solid $XY$ has $NaCl$ structure. If radius of $X^{+}$ is $100\text{pm}$, what is the radius of $Y^{-}$ ion?

Answer 1

$\text{For}NaCl\text{type crystal}$

$\frac{r_{+}}{r_{-}}=0.414\text{to}0.732$

$r_{-}=\frac{r_{+}}{0.414}=\frac{100}{0.414}=241.54\text{pm}$

$r_{-}=\frac{r_{+}}{0.732}=\frac{100}{0.732}=136.6\text{pm}$

ie., $r_{-}=136.6\text{to}241.54\text{pm}$