A certain crystalline substance that has a low melting point does not conduct electricity in solutio — Bonding Chemistry Question

STEPS:

1. Analyze the Melting Point: The substance has a low melting point. This indicates that the forces holding the individual particles together in the crystal lattice are relatively weak intermolecular forces (such as London dispersion forces, dipole-dipole interactions, or hydrogen bonds) rather than strong chemical bonds.
2. Evaluate Conductivity in the Liquid State: The substance does not conduct electricity when melted. Electrical conductivity in a liquid requires the presence of mobile charged particles, such as ions or delocalized electrons. The lack of conductivity suggests the substance is composed of neutral molecules that do not carry a charge.
3. Evaluate Conductivity in Solution: The substance does not conduct electricity in solution. This confirms that when the substance dissolves, it does not dissociate into ions (it is a nonelectrolyte), further supporting the idea that it is composed of stable, neutral molecules.
4. Identify the Solid Type: A solid that is crystalline, has low melting temperatures, and consists of neutral molecules that do not conduct electricity in any phase is the definition of a molecular solid.

WHY_OTHERS_WRONG:

• A) Covalent network solid: These substances (like diamond or $SiO_2$) are held together by a continuous network of strong covalent bonds, resulting in extremely high melting points, not low ones.
• B) Metallic solid: Metals contain delocalized valence electrons that allow them to be excellent conductors of electricity in both solid and liquid states.
• C) Polymer: While some polymers may have low melting points, they are typically very large, long-chain molecules and are often described differently in the context of "crystalline substances" compared to the primary classes of solids.
• D) Ionic solid: These are held together by strong electrostatic attractions between cations and anions, giving them high melting points. Additionally, while they do not conduct as solids, they conduct electricity very well when melted or dissolved because their ions become mobile.