For electrical conduction, free mobile electrons as seen in most metals must be present or ions which are charged particles must be available for solutions and molten substances.
Sodium chloride is an ionic compound without free mobile electrons or ions despite being ionic.
It will maintain a subtle and unique charge stability when in solid form.
In solid, the ions are not free to move and remain locked up in the solid mass.
When introduced into a solution, the ions becomes free to move and this will aid electrical conduction.
