Advanced Placement (AP) Chemistry Practice Exam

What results from unequal sharing of electrons in a molecule?

1. Formation of a single charge

2. Creation of a dipole moment

3. Complete ionization of the molecule

4. Substitution of atoms

The correct answer is: Creation of a dipole moment

Unequal sharing of electrons in a molecule often leads to the formation of a dipole moment. This occurs when there are significant differences in electronegativity between the atoms involved in a bond. When one atom attracts the shared electrons more strongly, it becomes partially negative, while the other atom becomes partially positive. This separation of charge creates a dipole, which is characterized by a dipole moment—a vector quantity that has both magnitude and direction, pointing from the positive to the negative charge. In polar covalent bonds, this effect results in molecules that have regions of partial positive and negative charges, which can significantly influence the molecule's physical and chemical properties, such as solubility, boiling and melting points, and interactions with other molecules. Understanding dipole moments is crucial for predicting how molecules behave in different environments, including their interactions with solvents in chemical reactions.