As we know that, if the bond is formed by the mutual sharing of electrons between the atoms, then it is called the covalent bond.

A covalent bond formed between two dissimilar atoms, the bond formed is said to be a polar covalent bond. A polar covalent bond is more stable than a pure covalent bond

The bond is formed between two dissimilar atoms means both having different electronegativities and which means the bond pair of electrons is not shared equally. The atom which is having high electronegativity, its bond pair shift towards the nucleus. As a result, the atom with higher electronegativity generally has a greater tendency to attract the electron towards itself.

This unsymmetrical distribution of electrons leads to partial charge separation. The electronegative atom acquires partial negative charged and the other atom acquires a slightly positive charge.

For example, HF, which contains a polar covalent bond (having different electronegativities). As we know that fluorine is more electronegative atom than the hydrogen. The electron pair shared between hydrogen and fluorine atoms, is, therefore, remains closer to the fluorine atom. As a result, fluorine acquires a partial negative charge and hydrogen acquires a partial positive charge.

To denote the partial charge on an atom, we use the symbol “δ”.

Electron pair is shifting towards

more electronegative atom, i.e., F

One more example:

Transfer of electron pair towards more electronegative chlorine.