Advanced Placement (AP) Chemistry Practice Exam

A polar molecule is characterized by having a net dipole moment, which arises from the presence of polar bonds within the molecule. Polar bonds form when there is a significant difference in electronegativity between two bonded atoms, leading to an uneven distribution of electron density. This results in one end of the bond becoming partially negative and the other end becoming partially positive, creating a dipole.

When a molecule contains one or more polar bonds arranged in such a way that their dipole moments do not cancel each other out, the molecule exhibits a net dipole moment, confirming its polarity. This means that there is an overall distribution of charge within the molecule that does not equal zero.

In contrast, a molecule with an equal distribution of charge or consisting entirely of nonpolar bonds would not be classified as polar. Similarly, symmetrical geometries often lead to dipole moments canceling out, resulting in a nonpolar molecule. Hence, the presence of a net dipole moment due to polar bonds is the defining characteristic of a polar molecule.