Which statement best describes molecular solids?

• A. Very hard and have very high melting points.
• B. Good conductors of electricity.
• C. Held together by metallic bonds.
• D. Atoms or molecules held together by London dispersion forces, dipole-dipole forces, or hydrogen bonds.

Answer: (D)

Molecular solids are held together by intermolecular forces, not by the strong bonds inside the molecules themselves. In these solids the units are discrete molecules, and they’re bound to each other by London dispersion forces, dipole-dipole attractions, and hydrogen bonds when present. These interactions are relatively weak compared with covalent or ionic bonds, so molecular solids typically have lower melting points, tend to be soft, and are poor conductors of electricity because electrons stay localized within molecules rather than moving freely through a lattice. That’s why describing molecular solids as held together by London dispersion forces, dipole-dipole forces, or hydrogen bonds best captures their nature. The other statements describe bonding in ionic, metallic, or covalent-network solids, which behave differently.