Which best describes a polar molecule?

A polar molecule is defined by its uneven distribution of electrical charge. This means that within the molecule, certain regions become partially positive while others become partially negative due to differences in electronegativity between the atoms involved. When two atoms with different electronegativities bond, the more electronegative atom attracts the shared electrons more strongly, creating an unequal charge distribution. This polarization leads to the characteristic dipole moment found in polar molecules.

For example, in a water molecule (H₂O), the oxygen atom is more electronegative than the hydrogen atoms, causing the electrons to spend more time closer to the oxygen. As a result, the oxygen side of the molecule becomes partially negative, and the hydrogen sides become partially positive. This uneven distribution results in many of the unique properties of water, such as its solvent capabilities and high surface tension.

In contrast, options describing equal charge distribution, symmetrical shape, or containing only one type of atom do not align with the definition of a polar molecule, as these characteristics are more typical of nonpolar molecules or elements in their pure form. Thus, the identification of a polar molecule hinges on recognizing its inherent dipole nature driven by uneven charge distribution.