Which of the following is not a type of molecular solid?

Amorphous solids

The correct answer is option 4. Amorphous solids.

Molecular solids are a type of crystalline solid where the constituent particles are molecules held together by intermolecular forces. There are three main types of molecular solids:

1. Nonpolar Molecular Solids: These are composed of nonpolar molecules. Held together by weak dispersion forces (van der Waals forces). Example: Solid noble gases like Argon, nonpolar organic compounds like naphthalene.

2. Polar Molecular Solids: These are composed of polar molecules. Held together by dipole-dipole interactions and dispersion forces. Example: Solid carbon dioxide (dry ice), ice.

3. Hydrogen Bonded Molecular Solids: These are composed of molecules with significant hydrogen bonding. Held together by hydrogen bonds. Example: Ice (solid H₂O), solid hydrogen fluoride.

4. Amorphous solids: On the other hand, amorphous solids are not a type of molecular solid. They are solids that do not have a long-range order or a well-defined crystalline structure. The particles in amorphous solids are arranged randomly. Examples include glass, plastics, and gels.

Nonpolar Solids, Polar Solids, and Hydrogen Bonded Solids are all types of molecular solids. Amorphous solids do not have a definite crystalline structure and are not considered molecular solids.