Question

The edge length of a $fcc$ ionic crystal is 508 pm. If the radius of cation is 110 pm, the radius of anion will be

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

Answer 1

Answer: (C)

144 pm

Answer 2

For ionic compounds,
Edge length $(a) = 2(r_+ + r_-)$
$508 = 2(110 + r_-)$
$508 = 220 + 2r_-$
$2r- = 508 - 220 = { 288\, pm}$
$r_- = {144 \,pm}$