Atomicity: The number of atoms constituting a molecule is known as its atomicity.

i. In I₂, there are two atoms of iodine constituting a molecule.

Hence, the atomicity is 2 (diatomic).

ii. In H₂S, there are two atoms of hydrogen and one atom of Sulphur constituting a molecule of H₂S. Hence, the atomicity is 3 (triatomic).

iii. In HNO₃, there are three atoms of oxygen, one atom of nitrogen and one atom of hydrogen sulphur constituting a molecule of HNO₃. Hence, the atomicity is five.

iv. In Na₂SO₄, there are two atoms of sodium, one atom of Sulphur and four atoms of oxygen constituting a molecule of Na₂SO₄ Hence, the atomicity is seven.

v. In S₈, there are eight atoms of sulphur constituting a molecule.

Hence, the atomicity is eight.