Question

Define valency.

Answer 1

Valency:

The combining capacity of the atom of an element with the atoms of other elements in order to acquire eight electrons (or two electrons in Helium) in its outermost shell is known as valency.

Example:

1. Consider a Sodium atom $\mathbf{\left(}\mathbf{Na}\mathbf{\right)}$ having atomic number $11$. Thus, the number of electrons in a Sodium atom are $11$.
2. The electronic configuration of Sodium is $(2,8,1)$.
3. In order to acquire eight electrons in the outermost shell, Sodium atom loses $1$ electron from the outermost shell.
4. Thus, the valency of Sodium is $1$.