Final answer:
To be polar, a molecule must have a separation of charge and a net dipole moment. The dipole moment is determined by the arrangement of polar bonds and the molecular structure.
Step-by-step explanation:
A whole molecule may also have a separation of charge, depending on its molecular structure and the polarity of each of its bonds. If such a charge separation exists, the molecule is said to be a polar molecule (or dipole); otherwise the molecule is said to be nonpolar. The dipole moment measures the extent of net charge separation in the molecule as a whole. We determine the dipole moment by adding the bond moments in three-dimensional space, taking into account the molecular structure.