Question

The edge of face centred unit cubic cell is $508$ pm. If the radius of the cation is $110$ pm, the radius of the anion is:

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

Answer 1

The correct option is A $144$ pm

Let us consider the problem.

For an fcc solid,edge length,$a=2(r^{+}+r^{-})$

$2\left(100+r^{-}\right)=508$

$\therefore 220+2r^{-}=508$

$\therefore 2r^{-}=508-220$

$\therefore 2r^{-}=288$

Therefore

$r^{-}=144pm$