Advanced Placement (AP) Chemistry Practice Exam

What type of forces exist between molecules in a covalently bonded substance?

1. Covalent bonds

2. Intermolecular forces

3. Ionic interactions

4. Metallic bonds

The correct answer is: Intermolecular forces

In a covalently bonded substance, the primary attractions between individual molecules arise from intermolecular forces. These forces are significantly weaker than the covalent bonds that hold atoms together within a molecule. Intermolecular forces include hydrogen bonding, dipole-dipole interactions, and London dispersion forces, all of which play a crucial role in determining the physical properties of covalently bonded compounds, such as boiling and melting points. Covalent bonds, while strongly holding the atoms within a molecule together, do not describe the interactions between separate molecules. Similarly, ionic interactions involve the electrostatic attraction between positively and negatively charged ions, which is not relevant in a substance formed by covalent bonds. Metallic bonds refer to the attraction between metal atoms and the delocalized electrons surrounding them, and also do not pertain to the molecular forces in covalent compounds. Thus, the presence of intermolecular forces is key in explaining the interactions between molecules in covalently bonded substances.