What defines a polar molecule?

A polar molecule is defined by its asymmetrical distribution of charge, which results from differences in electronegativity between the atoms involved. In a polar molecule, one end has a slight positive charge while the other end has a slight negative charge, creating a dipole moment. This charge imbalance occurs because electrons are not shared equally between the atoms; one atom tends to attract the shared electrons more strongly than the other, leading to the characteristic polarity of the molecule.

For instance, in water (H₂O), the oxygen atom is more electronegative than the hydrogen atoms. As a result, the electrons are pulled closer to the oxygen, creating a partial negative charge on that side of the molecule and partial positive charges on the hydrogen sides. This asymmetrical distribution is crucial for many physical and chemical properties of polar molecules, such as their interactions with other molecules and their solubility in different solvents.

The other options do not accurately describe polar molecules. An equal sharing of electrons indicates a nonpolar molecule, while a molecule without any bonds would not have the definition of a molecule at all. Additionally, describing a molecule as always gaseous does not pertain to its polarity; many polar molecules can exist in various states, including solid and liquid.