Question

Copper crystalises in an fcc lattice with a unit cell length of $360pm$. Find the radius of $Cu$ atom in $pm$.

Answer 1

(Refer to Image)

$4r=\sqrt{2}a$

where $a$ is the side of the square and $r$ is the radius

$2\sqrt{2}r=a\Rightarrow r=\frac{a}{2\sqrt{2}}=\frac{360}{2\sqrt{2}}pm$

$r=\frac{180}{\sqrt{2}}pm=127.3pm$