Copper crystallizes in a face-centred cubic lattice with a unit cell length of $361 \mathrm{pm}$. What is…

Copper crystallizes in a face-centred cubic lattice with a unit cell length of $361 \mathrm{pm}$. What is the radius of copper atom in pm?
  1. 108
  2. 128
  3. 157
  4. 181

Solution

$\mathrm{Cu} \rightarrow$ fcc lattice $\begin{aligned} &4 r=\sqrt{2} a\\ &\mathbf{r}=\frac{1}{2 \sqrt{2}} \mathbf{a}\\ &r=\frac{1}{2 \sqrt{2}} \times 361=128 \end{aligned}$

Asked in: NEET 2009 (Mains)

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