Question

What is the relation between the valency of an element and the number of valence electrons in its atoms? Explain.

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.

Valence electrons:

The electrons present in the outermost shell of the atom of an element are known as valence electrons.

Relationship between valency and valence electrons:

1. The valency of an element is determined by the number of valence electrons present in the atom of the elements.
2. The valency of an element can be calculated by knowing the number of valence electrons as only valence electrons take part in chemical bonding to achieve stable electronic configuration.
3. If the number of valence electrons is 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.
4. Thus, valency is equal to the number of valence electrons known, the number of electrons gained or lost or shared by the atom.

Example:

Valency of Sodium $\mathbf{\left(}\mathbf{Na}\mathbf{\right)}$:

1. Consider a Sodium atom $\mathbf{\left(}\mathbf{Na}\mathbf{\right)}$ having an 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$1$.

Valency of Fluorine $\mathbf{\left(}\mathbf{F}\mathbf{\right)}$:

1. Consider a Fluorine atom $\mathbf{\left(}\mathbf{F}\mathbf{\right)}$ having atomic number $9$. Thus, the number of electrons in a Fluorine atom are $9$.
2. The electronic configuration of Fluorine is $(2,7)$. The number of valence electrons is $7$.
3. In order to acquire eight electrons in the outermost shell, the Fluorine atom gains $1$ electrons.
4. Thus, the valency of Fluorine is $1$.