Why do ionic compounds conduct electricity when molten or dissolved, but not as solids?

• A. Because they have free mobile ions
• B. Because their electrons are delocalized like metals
• C. Because they share electrons
• D. Because they become magnets

Answer: (A)

The key idea is that conduction in ionic compounds comes from the movement of ions. In a solid, the ions are held in a rigid crystal lattice and cannot move, so there are no charge carriers that can drift in response to an electric field. When the substance is melted or dissolved, the lattice breaks apart and the ions become free to move. These mobile ions carry electric charge, allowing current to flow. The conduction is not due to electrons moving freely (as in metals) but to ions that act as the charge carriers. Sharing electrons describes covalent bonding, not this mechanism, and magnets aren’t involved in enabling electrical conduction.