1. In a body centered cubic unit cell, each corner is occupied by an identical particle and in addition to that one atom occupied the body centre.
2. Those atoms which occupy the corners do not touch each other, however they all touch the one that occupies the body centre.
3. Hence each atom is surrounded by eight nearest neighbours and coordination number is 8. An atom present at the body centre belongs to only a particular unit cell i.e., unshared by other cell.
∴number of atoms in a bcc unit cell = \(\frac{N_c}{8}+\frac{N_b}{1}+\frac{8}{8}\) = \(\frac{1}{1}\) = 1 + 1 = 2
