Write down the formulae of

(i) Sodium oxide

(ii) Aluminium chloride

(iii) Sodium sulphide [3 MARKS]​

Each point: 1 Mark

1. Sodium oxide:
Symbol: Na O
$\searrow \swarrow$
Valency: 1 2
Criss crossing the valencies we get the formula as Na₂O.

2. Aluminium chloride:
Symbol: Al Cl
$\searrow \swarrow$
Valency: 3 1
Criss crossing the valencies we get the formula as AlCl₃.

3. Sodium sulphide:

Symbol: Na S
$\searrow \swarrow$
Valency: 3 1
Criss crossing the valencies we get the formula as Na₂S.