CBSE Class 9 Answered

The valency of an element is the ability of that element to combine with other elements. The valency is determined by the number of electrons in the outer shell of each atom of an element.

The following steps are used to calculate the valency of an element:

1. Atomic number of the element is noted.
2. Electronic configuration of the element is noted.
3. The number of electrons in the outer most shell is noted.
4.  If the number of electrons in the outer most shell is less than four, then the valency of the substance is the number itself.
5.  If the number of electrons is more than 4 but less than 8, then subtract the number by 4 to get the valency.

Example: Determine the valency of sulphur

1.         i.            Atomic number of sulphur=16
2.       ii.            Electronic configuration= 2,8,6
3.     iii.            the number of electrons is more than 4 but less than 8, therefore

Valency = 8 – 6= 2

Hence, Valency of sulphur=2