Question

In a body centred and face centred arrangement of atoms of an element, what will be the number of atoms present in respective unit cells? Justify your answer with a calculation.

Answer 1

In bed unit cell, the atoms are present only at the comers of a cube.

Total number of atoms in one unit cell = `8 xx 1/8 = 1`

In face centred cubic unit cell,

The atoms are present at the comers as well as at the centres of six faces of a cube.

Total number of atoms in one unit cell

`= 8 xx 1/8 + 6 xx 1/2`

= 1 + 3 = 4