Question

An ionic compound AB has a $ZnS$ type of structure, if the radius $A^{+}$ is 22.5 pm, then the ideal radius of $B^{-}$ so as not to cause any distortion is (in pm):

Answer 1

Since, the ionic compound AB has a $ZnS$ type of structure, therefore it has tetrahedral holes, for which
$\frac{\text{Radius of Cation}}{\text{Radius of Anion}}=0.225$
$\frac{r^{+}}{r^{-}}=0.225$
$\frac{22.5}{r^{-}}=0.225$
$\therefore r^{-}$ = 100 pm