Question

What do you understand by term valency?

Answer 1

Valency: The number of electrons gained, lost, or shared by the atom of an element so as to complete its octet (or duplet in the case of elements having only a K shell) is called the valency of the element.

1. The valency of an element = number of valence electrons(when the number of valence electrons is from 1 to 4)
2. The valency of an element = 8– the number of valence electrons. (when the number of valence electrons is more than 4)

Example:

1. The valency of a sodium $\left(\mathrm{Na}\right)$ element. Its electronic configuration is 2, 8, 1 (The number of valence electrons is 1) = number of valence electrons= 1
2. The valency of an oxygen $\left(\mathrm{O}\right)$element. Its electronic configuration is 2,6 (The number of valence electrons is 6)= 8–6=2.