Question

Define covalency.

Answer 1

Covalency:

The number of electrons shared by an atom with another atom during the formation of covalent molecule to have eight electrons in its outermost shell is known as covalency.

Example:

1. Consider a Hydrogen atom $\mathbf{\left(}\mathbf{H}\mathbf{\right)}$ having atomic number $1$. Thus, the number of electrons in a Hydrogen atom are $1$.
2. The electronic configuration of Hydrogen is $\left(1\right)$.
3. In order to form Hydrogen molecule $\left(H_2\right)$, two Hydrogen atoms share one electron each and attain stable nearest noble gas configuration.
4. As one Hydrogen atom shares one electron, the covalency of Hydrogen is $1$.

Examples of elements exhibiting covalency:

Hydrogen $\mathbf{\left(}\mathbf{H}\mathbf{\right)}$, Chlorine $\mathbf{\left(}\mathbf{Cl}\mathbf{\right)}$, Oxygen $\mathbf{\left(}\mathbf{O}\mathbf{\right)}$, Carbon $\mathbf{\left(}\mathbf{C}\mathbf{\right)}$.