Question

Number of atoms per unit cell in B.C.C. is:

• A. 9
• B. 4
• C. 2
• D. 1

Answer 1

Answer: (C)

2

In BCC, lattice atoms occupies the corners and body center of a cube.

Each corner has a contribution of $\frac{1}{8}$ and there are 8 corners in a cube. Effective no.of atoms in a cube = $\frac{1}{8}\times 8=1$

Also, a body centre will have contribution of 1 and each cube will have 1 body centre. So effective number of atoms in a cube= 1. So total number of atoms in BCC = 1+1 = 2.

So the answer is option C.