Q51 / 197 · NEET 2009 (Mains) · Chemistry
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?
- A108
- Correct answerB128
- C157
- D181
Solution
$\mathrm{Cu} \rightarrow$ fcc lattice
$$ \begin{aligned} &4 r=\sqrt{2} a\\ &\mathbf{r}=\frac{1}{2 \sqrt{2}} \mathbf{a}\\ &r=\frac{1}{2 \sqrt{2}} \times 361=128 \end{aligned} $$
$$ \begin{aligned} &4 r=\sqrt{2} a\\ &\mathbf{r}=\frac{1}{2 \sqrt{2}} \mathbf{a}\\ &r=\frac{1}{2 \sqrt{2}} \times 361=128 \end{aligned} $$
Hence, the correct answer is option: 'B'.