Question

The edge length of an FCC cell of a salt $X$ is $508pm$. If the radius of the cation is $110pm$, the radius of an anion is:

• A. $110pm$
• B. $220pm$
• C. $285pm$
• D. $144pm$

Answer 1

The correct option is D $144pm$

For FCC type, (NaCl type structure)

The relation between edge length and radius of cation and anion is given as:

$2(r^{+}+r^{-})=a$

$2(110+r^{-})=508$

$r^{-}=\frac{288}{2}=144pm$

Hence, Option "D" is the correct answer.