Polar and nonpolar covalent bonds
There are two types of bond – polar and nonpolar. It depends on the electronegativity of bonding atoms.
Consider two atoms which are similar or identical having similar electronegativity take part in covalent bonding. The electron pair forming the bond is shared equally between two atoms so the formed bond is nonpolar here the distribution of electron density is equal.
But if two bonding atoms having dissimilar electronegativity the bond will be polar.
Because the pair of electron forming will get shifted towards the atom which has more electronegativity and show more electronegative atom requires partial negative charge while another atom will acquire partial positive charge so the bond formed between this atoms has partial ionic character and known as polar covalent bond.
In general, we can say that when two atoms of different radii and different electronegativities combine to share an electron pair the polar bond is developed.
Polar covalent bonds are partially ionic in nature and are strong due to electrostatic attraction between two poles.
How to identify polar and nonpolar Bond
If covalent bonding formation takes place between identical atoms it must be non-polar. So we can consider electronegativity difference. If we know the value of electronegativity of bonding atoms, we can find out the difference and predict the polarity or nonpolar it.