Which type of compound is least likely to conduct electricity?

Covalent molecular compounds are least likely to conduct electricity because they do not have charged particles that can move freely. Unlike metallic and ionic compounds, which either have delocalized electrons or ions in a solution to facilitate conductivity, covalent molecular compounds consist of discrete molecules held together by covalent bonds. These molecules do not dissociate into ions in a solid state or when dissolved in a solvent.

In contrast, metallic compounds can conduct electricity due to the presence of delocalized electrons that can move throughout the metal lattice. Ionic compounds, when dissolved in water or molten, dissociate into ions, allowing electrical current to flow. Mixed ionic-covalent compounds may also conduct electricity due to the presence of ions. Thus, the inability of covalent molecular compounds to generate free-flowing charged particles is why they are least likely to conduct electricity.