Question

The number of atoms contained in one face-centred cubic unit cell of a monoatomic substance is ______.

Options

• 1

• 2

• 4

• 3

Answer 1

The number of atoms contained in one face-centred cubic unit cell of a monoatomic substance is 4.

Explanation:

In a face-centred cubic (fcc) unit cell, atoms are present at 8 corners and 6 face centres. Each corner atom contributes `1/8` and each face atom contributes `1/2`, so

Total number of atoms = `8 xx 1/8 + 6 xx 1/2`

= 1 + 3

= 4 atoms