Electrostatics — Physics STD 12 Science — Question

Polar molecules: The molecules in which “centre of gravity” of positive nuclei and revolving electrons do not coincide are known as polar molecules.
Example: HCl, H2O, N2O etc.
Polar substances behave as a tiny electric dipole because polar molecules have a permanent electric dipole moment.
Non-polar molecules: The molecules in which “centre of gravity” of positive nuclei and revolving electrons coincide are known as non-polar molecules.
Example: O2, H2, CO2, polyethelene, polystyrene etc.
Non-polar molecules do not have permanent electric dipole moment because of their
symmetry.