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)

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