What characteristic defines a polar molecule?

A polar molecule is characterized by a distribution of electrical charge that leads to the formation of distinct positive and negative ends, commonly referred to as poles. This occurs due to differences in electronegativity between the atoms involved in the bond, causing one end of the molecule to become more negative while the other end becomes more positive. For example, in water (H₂O), the oxygen atom is more electronegative than the hydrogen atoms, resulting in a partial negative charge near the oxygen and a partial positive charge near the hydrogens. This separation of charge creates a dipole moment, which is a hallmark of polar molecules.

The other options describe different characteristics that do not align with what defines polarity in molecules. An equal distribution of electrical charge typically occurs in nonpolar molecules, while a lack of electrical charge suggests there are no charges to create polarity. The absence of dipoles would mean that the molecule has no separation of charge, again indicating nonpolarity. Thus, the presence of a charge distribution that results in positive and negative ends is crucial in categorizing a molecule as polar.