<P> Because electrons have a negative charge, the unequal sharing of electrons within a bond leads to the formation of an electric dipole: a separation of positive and negative electric charge . Because the amount of charge separated in such dipoles is usually smaller than a fundamental charge, they are called partial charges, denoted as δ + (delta plus) and δ − (delta minus). These symbols were introduced by Christopher Kelk Ingold and Edith Hilda Ingold in 1926 . The bond dipole moment is calculated by multiplying the amount of charge separated and the distance between the charges . </P> <P> These dipoles within molecules can interact with dipoles in other molecules, creating dipole - dipole intermolecular forces . </P> <P> Bonds can fall between one of two extremes--being completely nonpolar or completely polar . A completely nonpolar bond occurs when the electronegativities are identical and therefore possess a difference of zero . A completely polar bond is more correctly called an ionic bond, and occurs when the difference between electronegativities is large enough that one atom actually takes an electron from the other . The terms "polar" and "nonpolar" are usually applied to covalent bonds, that is, bonds where the polarity is not complete . To determine the polarity of a covalent bond using numerical means, the difference between the electronegativity of the atoms is used . </P> <P> Bond polarity is typically divided into three groups that are loosely based on the difference in electronegativity between the two bonded atoms . According to the Pauling scale: </P>

Do all polar molecules have a dipole moment