Question

An ionic compound AB has ZnS type structure. If the radius $A^{+}$ is $22.5$ pm, then the ideal radius (in pm) of $B^{-}$ would be :

• A. $54$
• B. $100$
• C. $145$
• D. none of the above

Answer 1

The correct option is B $100$

$B^{-}$ occupies ccp while $A^{+}$ occupies alternate tetrahedral voids.

$r=0.225R$

Where r is the radius of $A^{+}$ and R is the radius of $B^{-}$

$22.5=0.225R$

$R=100$ pm

Hence, the ideal radius of $B^{-}$ would be $100$ pm.

Hence, the correct option is $\text{B}$