Chemistry – Atoms, elements and compounds - Simple molecules and covalent bonds | e-Consult

Simple molecular compounds are poor conductors of electricity because they do not contain free electrons. Electrical conductivity requires the presence of mobile charge carriers, typically electrons.

In molecular compounds, the electrons are shared between the atoms in covalent bonds. They are not free to move throughout the structure. The electrons are localized within the bonds and are not delocalized as they are in metals or ionic compounds.

For a substance to conduct electricity, it needs a source of free electrons. Metals have a 'sea' of delocalized electrons that can move easily and carry charge. Ionic compounds have ions that can move and carry charge. Molecular compounds lack this mobility. Therefore, even if an electric field is applied, the electrons within the covalent bonds cannot move freely to conduct electricity.