Match the chemical formulae with the corresponding compounds.

Sodium chloride: Symbol of sodium is Na and its valency is 1; symbol of chlorine is Cl and its valency is 1. Criss-crossing the valencies, the formula of the compound will be $\text{NaCl}$.

Lithium oxide: Symbol of lithium is Li and its valency is 1; symbol of oxygen is O and its valency is 2. Criss-crossing the valencies, the formula of the compound will be ${\text{Li}}_2\text{O}$.

Aluminium oxide: Symbol of aluminium is Al and its valency is 3; symbol of oxygen is O and its valency is 2. Criss-crossing the valencies, the formula of the compound will be ${\text{Al}}_2{\text{O}}_3$.

Hydrogen bromide: Symbol of hydrogen is H and its valency is 1; symbol of bromine is Br and its valency is 1. Criss-crossing the valencies, the formula of the compound will be $\text{HBr}$.