Solid State - Result Question 13
####13. A metal crystallises in a face centred cubic structure. If the edge length of its unit cell is ’ $a$ ‘, the closest approach between two atoms in metallic crystal will be
(2017 Main)
(a) $2 a$
(b) $2 \sqrt{2} a$
(c) $\sqrt{2} a$
(d) $\frac{a}{\sqrt{2}}$
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Answer:
Correct Answer: 13. (d)
Solution:
- For fcc arrangement, $4 r=\sqrt{2} a$
where, $r=$ radius and $a=$ edge length
$\therefore$ Closest distance $=2 r=\frac{\sqrt{2} a}{2}=\frac{a}{\sqrt{2}}$
