Question

A solid AB has ZnS type structure. If the radius of the anion $B^{-}$ is $100$ pm, then the minimum radius (in pm) of the cation $A^{+}$ will be :

• A. $192.3$
• B. $414$
• C. $22.5$
• D. $44.4$

Answer 1

The correct option is C $22.5$

AB has ZnS structure (ccp structure).
$Z{n}^{+}$ ions has tetrahedral voids and radius of tetrahedral $=0.225$
$r_{A^{+}}=0.225\times r_{B^{-}}$
$r_{A^{+}}=0.225\times 100$
$r_{A^{+}}=22.5$ pm
Hence, the minimum radius of the cation $A^{+}$ will be $22.5$ pm.