Question

Copper crystallises in a face-centred cubic lattice with a unit cell length of $361\text{pm}$. What is the radius of copper atom in $\text{pm}$?

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

Answer 1

The correct option is D $128$

Since, $Cu$ crystallises in a face centered cubic lattice,
atomic radius will be, $r=\frac{a}{2\sqrt{2}}(a=\text{edge length})\therefore r=\frac{361\text{pm}}{2\sqrt{2}}=127.6\text{pm}\approx 128\text{pm}$