Question

Why are molecular solids soft and possess low melting and boiling points?

Answer 1

1. Molecular solids are made up of neutral molecules held together by weak intermolecular forces, such as van der Waals forces, dipole-dipole interactions, or hydrogen bonds (in some cases).
2. These forces are much weaker than the strong ionic or covalent bonds found in other types of solids. As a result the molecules can be easily displaced, making the solid soft. Less energy is required to break these weak forces, leading to low melting and boiling points.
3. The molecules in molecular solids are not tightly packed, and since the bonding between them is weak, they can be easily displaced. This makes molecular solids soft and easily compressible.
4. Examples: Dry ice (CO₂), iodine (I₂), and ice (H₂O).