Question

The edge length of rock salt type unit cell is $508pm$. If the radius of the cation is $110pm$, the radius of the anion assuming $NaCl$ type structure is:

• A. $144pm$
• B. $398pm$
• C. $288pm$
• D. $618pm$

Answer 1

The correct option is A $144pm$

In $NaCl$ type structure

$2(r_{N{a}^{+}}+r_{C{l}^{-}})=508pm$ (along edge length)

$r_{N{a}^{+}}=110$

$\Rightarrow r_{C{l}^{-}}=254-110=144$ $pm$