Question

What is the number of atoms in a body-centred cubic (bcc) unit cell of an element?

At room temperature, iron crystallises in a body-centred cubic structure. How many atoms are associated with its unit cell?

Calculate the number of particles per unit cell in a body-centred cubic system.

In a body-centred arrangement of atoms of an element, what will be the number of atoms present in respective unit cells?

Answer 1

The BCC unit cell has 8 atoms at the corners.

∴ Each corner atom is shared by 8 unit cells = `8 xx 1/8`

= 1 atom

∴ 1 body-centred atom is completely inside the unit cell (not shared) = 1 × 1 

= 1 atom

∴ Total number of atoms = 1 (from corners) + 1 (from center)

= 2 atoms per unit cell

Thus, the unit cell of a body-centred cubic system contains 2 atoms.