A polar covalent bond occurs when two atoms share electrons unequally due to differences in their electronegativities. Electronegativity is a measure of an atom's ability to attract electrons. In a polar covalent bond, one atom pulls the shared electrons closer, creating a slight electrical charge, or dipole, where one end is slightly negative and the other slightly positive. Water (H2O) is a common example of a molecule with polar covalent bonds. In water, the oxygen atom is more electronegative than the hydrogen atoms, causing the electrons to be drawn closer to oxygen. This results in a partial negative charge on the oxygen and a partial positive charge on the hydrogens, giving water its unique properties.