What is the difference between polar and nonpolar covalent bonds?
The difference is in the relative electronegativities of the bonded atoms. Electronegativity is a measure of the strength of an atoms attraction for electrons in a bond. If an atom with high electronegativity is bound to one with low, then a polar covalent bond will result. If they are equal, or close, it is non-polar. It is analogous to a tug of war with the electrons. They atom that pulls harder keeps the electrons longer so it is slightly more negative and it bond partner is more positive.
