Q55 / 197 · NEET 2009 (Mains) · Chemistry

Lithium metal crystallizes 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 lithium will be :

  • A
    $300.5 \mathrm{pm}$
  • B
    $240.8 \mathrm{pm}$
  • Correct answer
    C
    $151.8 \mathrm{pm}$
  • D
    $75.5 \mathrm{pm}$

Solution

For bcc type of unit cell $$ \begin{aligned} \sqrt{3} \mathrm{a} & =4 \mathrm{r} \\ \mathrm{r} & =\frac{\sqrt{3}}{4} \mathrm{a} \\ & =\frac{1.732 \times 351}{4} \\ & =151.98 \end{aligned} $$

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

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