Question

A metal crystallises as fcc crystal structure. If edge length of unit cell is 320 pm then the radius of the metal atom approximately will be:

• A. 139 pm
• B. 178 pm
• C. 160 pm
• D. 113 pm

Answer 1

The correct option is D 113 pm

For fcc unit cell
$\sqrt{2}a=4r$
(where a = edge length, r = radius of atom)

Or, $r=\frac{\sqrt{2}}{4}a=\frac{\sqrt{2}}{4}\times 320r=113pm$