The steps involved in writing the formula for a compound are as follows:
1. Note down the symbols of the elements or their radicals. Then note down the valencies as superscript on the symbols of the elements.
2. If there is a common factor in the valencies, then divide it to a simple one.
3. Exchange the valencies and write them as subscripts.
[Note: If the radicals contain more than 2 atoms, they will be written in brackets and the exchanged valence number is written as subscript.]
Let's use the above steps for writing the formula for calcium chloride.
* The elements in calcium chloride are calcium and chlorine. The valency of calcium is 2 and chlorine is 1. Therefore, we write the symbols as Ca2 and Cl1.
* The common factor among the numbers 1 and 2 is nil.
* The valencies are exchanged and written as subscripts to the elements. Therefore, the formula of calcium chloride would be CaCl2.
Answers
Answer: 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.
Explanation: