Question

Work out the formulae for the following compounds :
(a) Sodium oxide
(b) Calcium carbonate

Answer 1

(a) Valency of Sodium = 1
Valency of Oxygen = 2



Formula for sodium oxide can be worked out by crossing the valencies of the constituent elements.
Therefore, formula for sodium oxide is: Na₂O.

(b) Valency of Calcium = 2
Valency of Carbonate ion = −2



Formula for calcium carbonate can be worked out by crossing the valencies of the constituent elements/ions. +2 positive charge of calcium neutralizes the −2 negative charge of carbonate ion.
Therefore, formula for calcium carbonate is: CaCO₃.