Polarity is defined as the formation of opposite charges on the atoms of a compound due to the difference in their electronegativities.
For example, in a HCl molecule chlorine is more electronegative in nature as compared to the hydrogen atom.
Hence, chlorine will attract the valence electron of hydrogen atom more towards itself. Due to this a partial positive charge will develop on hydrogen atom and a partial negative charge will develop on the chlorine atom.
Thus, we can conclude that polarity of bonds and molecules is determined by the difference in electronegativity of the atoms involved.
