The Solid State Ques 27
27. The number of atoms contained in an $f c c$ unit cell of a monoatomic substance is
[1993]
1
2
4
6
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Answer:
Correct Answer: 27.(c)
Solution:
(c) The number of atoms in a unit cell may be calculated by the formula
$ Z=\frac{n_c}{8}+\frac{n_b}{1}+\frac{n_f}{2}+\frac{n_e}{4} $
where $n_c=$ no. of atom at the corner $n_b=$ no. of atoms at body centre $n_f=$ no. of atoms at face centre, $n_e=$ no. of atoms at edge centre.
An $f c c$ crystal contains
$ =\frac{8}{8}+\frac{6}{2}=4 \text{ atoms per unit cell. } $
BETA
