Question

Copper crystallizes in fcc with a unit cell length of $361$ pm. What is the radius (in pm) of copper atom?

• A. $109$
• B. $127$
• C. $157$
• D. $181$

Answer 1

Answer: (B)

$127$

For FCC the relation between radius and the edge length is as follows

$\sqrt{2}a=4r$

$\therefore r=\frac{\sqrt{2}\times a}{4}=\frac{\sqrt{2}\times 361}{4}=127.6$ pm
Option B is correct.