Question

How is the valency of an atom determined?

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.

Determining the valency of an atom:

1. The valency of an atom is determined by the number of electrons present in the valence shell of that atom.
2. If the number of valence electrons are known, the number of electrons gained or lost or shared by the atom in order to acquire eight electrons in its outermost shell can be known.
3. For the atoms having more than 4 valence electrons, valency= 8 - valence electrons.

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 $(2,8,1)$. The number of valence electrons is $1$.
3. In order to acquire eight electrons in the outermost shell, Sodium atom loses $1$ valence electron.
4. Thus, the valency of Sodium is $1$.