When atoms in a molecule do not share their electrons equally, a polar covalent bond forms. In a polar covalent bond, the electrons are pulled more strongly towards one atom than the other. This creates a partial positive charge on the atom that is losing electrons and a partial negative charge on the atom that is gaining electrons. The polarity of a covalent bond is determined by the difference in electronegativity between the two atoms. Electronegativity is a measure of an atom's ability to attract electrons. The greater the difference in electronegativity between two atoms, the more polar the covalent bond will be.
