Question

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

• A. 157 pm
• B. 128 pm
• C. 108 pm
• D. 181 pm

Answer 1

Answer: (B)

128 pm

Answer 2

For FCC,
$r=\frac{\sqrt{2}a}{4}=\frac{a}{2 \sqrt{2}}=0.3535 a$
given $a = 361 \,pm$
$r=0.3535 \times361$
$= 128 \,pm$