Question

Write the formulae of the following compounds, showing the steps involved.

(a) sodium oxide
(b) magnesium nitrate
(c) magnesium sulphate
(d) aluminium chloride

Answer 1

Let's write the formula of the given compounds along with the steps involved.
a. Sodium oxide
* The elements in sodium oxide are sodium and oxygen. The valency of sodium is 1 and oxygen is 2. Therefore, we write the symbols as Na₁ and​ O₂.
* The common factor among the numbers 1 and 2 is nil.
* The valencies are exchanged and are written as subscripts to the elements. Thus, the formula of sodium oxide would be Na₂O.


b. Magnesium nitrate
* Magnesium nitrate contains the element magnesium and nitrogen. The valency of magnesium is 2 and radical of nitrogen is 1. Therefore, we write the symbols as Mg₂ and (NO₃)_1.
* The common factor among the numbers 1 and 2 is nil.
* The valencies are exchanged and written as superscripts to the elements. As the radical contains more than 2 atoms, the radical is written in brackets and the exchanged valency is written as its subscript. Thus, the formula of magnesium nitrate would be Mg (NO₃)₂.


c. Magnesium sulphate
* Magnesium sulphate contains the element magnesium and sulphur. The valency of magnesium is 2 and that of the radical of sulphur is also 2. Therefore, we write the symbols as Mg2 and ​(SO4)₂.
* The common factor among the numbers 2 and 2 is one.
* As both the element and radical’s valencies are one, neither the radical will not be written in brackets nor the valency number will be written as a subscript. Thus, the formula of Magnesium sulphate would be MgSO₄.


d. Aluminium chloride
* The elements in aluminium chloride are aluminium and chlorine. The valency of aluminium is 3 and chlorine is 1. Therefore, we write the symbols as Al₃ and ​Cl₁.
* The common factor among the numbers 1 and 3 is nil.
* The valencies are exchanged and are written as subscripts to the elements. Thus the formula of aluminium chloride would be AlCl₃.