Polarity - Dipole:
Polarity results from the uneven partial charge distribution
between various atoms in a compound. Atoms, such as nitrogen,
oxygen, and halogens, that are more electronegative have a tendency
to have partial negative charges. Atoms, such as carbon and hydrogen,
have a tendency to be more neutral or have partial positive charges.
Electrons in a polar covalent bond are unequally shared between
the two bonded atoms, which results in partial positive and negative
charges. The separation of the partial charges creates a dipole.
The word dipole means two poles: the separated partial positive
and negative charges. A polar molecule results when a molecule
contains polar bonds in an unsymmetrical arrangement.
Nonpolar molecules are of two types. Molecules whose atoms
have equal or nearly equal electronegativities have zero or very
small dipole moments. A second type of nonpolar molecule has
polar bonds, but the molecular geometry is symmetrical allowing
the bond dipoles to cancel each other.