Question

The edge length of a face centered cubic cell of an ionic substance is 508pm. If the radius of cation is 110pm, the radius of anion is:

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

Answer 1

Answer: (D)

144 pm

Given,

$r^{+}=110pm$

$a=508pm$

For FCC structure,

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

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

$2r^{-}=508-220=288pm$

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

The correct option is D.