Solid State - Result Question 14
####14. Sodium metal crystallises in a body centred cubic lattice with a unit cell edge of $4.29 \AA$. The radius of sodium atom is approximately
(a) $1.86 \AA$
(b) $3.22 \AA$
(c) $5.72 \AA$
(d) $0.93 \AA$
(2015 Main)
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Answer:
Correct Answer: 14. (a)
Solution:
- For bcc unit cell, $\sqrt{3} a=4 a$
$$ \begin{aligned} r & =\frac{\sqrt{3}}{4} a \\ & =\frac{\sqrt{3}}{4} \times 4.29 \AA=1.85 \AA \\ r & =1.85 \AA \approx 1.86 \AA \end{aligned} $$
