Question

What happens to electrons when a polar covalent bond forms?

Answer 1

They are unequally shared about the species.

Explanation:

Consider the diagram of `CH_4` and look for a perspective dipole moment:

In the C-H bonds, the electron are shared unequally between Carbon and Hydrogen. The dipole points toward Carbon because the C-H bond is polar covalent, and this is because Carbon is more electronegative than Hydrogen.

However in `CH_4`, the dipoles created by the C-H bonds cancel each other out, and as you can observe there is no dipole moment.