Work out the formula for sulphur dioxide. (Valencies : S = 4; O = 2)

Valency of Sulphur = 4

Valency of Oxygen = 2

Elements :  S              O

Valency   :  4               2

Formula for sulphur dioxide can be worked out by crossing the valency of the constituent elements.

Thus, formula of sulphur dioxide is S₂O₄.

The formula has a common factor of 2.

Therefore, dividing the formula by the common factor gives chemical formula: SO₂.