Q75 / 200 · NEET 2009 (Screening) · Chemistry

Lithium metal crystallises in a body centred cubic crystal. If the length of the side of the unit cell of lithium is $351 \mathrm{pm}$, the atomic radius of the lithium will be

  • A
    $240.8 \mathrm{pm}$
  • Correct answer
    B
    $151.98 \mathrm{pm}$
  • C
    $75.5 \mathrm{pm}$
  • D
    $300.5 \mathrm{pm}$

Solution

In case of body centred cubic (bcc) crystal, $\mathrm{a} \sqrt{3}=4 \mathrm{r}$ Hence, atomic radius of lithium, $\mathrm{r}=\frac{\mathrm{a} \sqrt{3}}{4}$ $\begin{aligned} & =\frac{351 \times 1.732}{4} \\ & =151.98 \mathrm{pm} \end{aligned}$

Hence, the correct answer is option: 'B'.

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