Question

Copper crystallises in fcc with a unit cell length of 361 pm. What is the radius of copper atom ?

• A. 127 pm
• B. 157 pm
• C. 181 pm
• D. 108 pm

Answer 1

Answer: (A)

127 pm

Answer 2

In fcc unit cell 4r = $\sqrt { 2 } a$ [r = radius of Cu atom, a = edge length]

So r = $\frac{\sqrt{2}a}{4}$

r = $\frac{\sqrt{2} \times 361}{4}$= 127 pm.