What is a polar covalent bond?
A covalent bond whose shared pair of electrons tend to lie closer to one of the two atoms forming the bond is called a polar covalent bond .
The atom which tends to attract these shared electrons, or more precisely speaking, the electron density of the bond towards itself is said to be electronegative .
For example, the bond between H and F in an HF molecule is a polar covalent bond. The F atom being more electronegative tends to attract the shared electrons towards itself.
This exaggerated animation should help in understanding what goes on between the two atoms :) :
A polar covalent bond is a bond between two atoms in which the electrons are shared unequally.
Due to differences in electronegativity, different atoms will have a stronger pull on electrons, creating a dipole. This can be seen in water, H20. The oxygen atom has a much higher electronegativity than the hydrogen atoms. This leads the electrons shared between the atoms to spend a majority of their time in space around the oxygen atom. Because electrons carry a negative charge, their increased presence around oxygen creates a partially negative pole there, and their absence from hydrogen creates a partially positive pole on the opposing end.