A salt which does not conduct electricity in the solid state becomes a good conductor in molten state because, in the solid ionic compound, the ions are held together in fixed positions by strong electrostatic forces and cannot move freely as a result of the attractive forces acting between them. But on the other hand, when we dissolve the ionic solid in water or melt it, the crystal structure is broken down and ions become free to move and conduct electricity. Thus, an aqueous solution of an ionic compound conducts electricity because there are plenty of free ions in the solution which are able to conduct electric current.