State the formula of each of the following compounds.

(a) Calcium nitrate

(b) Sodium chloride

(c) Magnesium sulphate

(d) Ammonium bicarbonate

(e) Aluminium oxide

(a) Calcium nitrate

Symbol Ca NO₃

Valency: Ca²⁺ NO₃^1-

1- 2+

Formula: Ca(NO₃)₂

(b) Sodium chloride

Symbol Na Cl

Valency: Na²⁺ Cl^2-

2- 2+

Formula: Na₂Cl₂ = NaCl

(c) Magnesium sulphate

Symbol Mg SO₄

Valency: Mg²⁺ SO₄^2-

2- 2+

Formula: Mg₂(SO₄)₂ = MgSO₄

(d) Ammonium bicarbonate

Symbol NH₄ HCO₃

Valency: NH₄⁺¹ HCO₃^1-

1- 1+

Formula: NH₄HCO₃

(e) Aluminium oxide

Symbol Al O

Valency: Al³⁺ O^2-

2- 3+

Formula: Al₂O₃