Question

Copper crystallises as an FCC unit cell. If the atomic radius of copper is $1.28\mathring{A}$, then what is the edge length (in $\mathring{A}$) of the unit cell?

• A. $2.16$
• B. $3.63$
• C. $3.97$
• D. $4.15$

Answer 1

Answer: (B)

$3.63$

Copper crystallises as an FCC unit cell.
Here, $4r=a\sqrt{2}$, where r is the atomic radius and a is the edge length of the unit cell.
$a=\frac{4r}{\sqrt{2}}=\frac{4\times 1.28}{\sqrt{2}}=3.63\mathring{A}$