Question

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

• A. $110pm$
• B. $144pm$
• C. $618pm$
• D. $398pm$

Answer 1

The correct option is B $144pm$

Distance between centres of cation and anion $=\frac{d}{2}=\frac{508}{2}=254pm$

$r_c+r_a=254pm$

or $110+r_a=254$

or $r_a=144pm$.