Question

Calculate the number of atoms in a cubic unit cell having one atom on each corner and two atoms on each body diagonal.

Answer 1

Answer: 9

There are $8$ corners in a cubic unit cell and each has one atom shared by $8$ cubic unit cells.
$8$ corner $\times 1/8$ atom per unit cell $=1$ atom
There are four body diagonals in a cubic unit cell and each has two body centre atoms.
So, $4\times 2=8$ atoms
Therefore, total number of atoms per unit cell
$=1+8=9$.