What are polar and non-polar covalent bonds ?

Explanation

(i) Non polar covalent bond
when a bond is formed between two similar atoms, the shared pair of electron is equally distributed among similar atoms. The electron pair is exactly situated between the two identical nuclei, the bond so formed is called nonpolar covalent bond. For example, in `H_(2), O_(2), Cl_(2), N_(2)" and "F_2` etc.
(ii) Polar covalent bond
when a bond is formed between two differnet atoms, the shared electron pair between the two atoms gets displaced more towards the highly electronegative atom. Here, electronegative atom acquires partial negative charge and other atom acquires partial positive charge. the poles are developed in between them and bond is called polar covalent bond. For example,
`H:underset(..)overset(..)(Cl):" or "overset(delta+)(H)-overset(delta-)(Cl)`
In HCl ,Cl is more electronegative, hence it altracts shared pair of electrons towards itself and acquires partial negative charge whereas hydrogen acquires partial positive charge. this causes some ionic character in a covalent bond of `HCl`.