Why is ionic solid non-conductive, yet its solutions in water, or in the liquid state, it carries a charge?
Simple, binary ionic solids are composed of a positive ion and and a negative ion. In the solid state they are not free to move. In the liquid or molten state, they are free to move, and can therefore carry a current.
Take a simple salt such as
If the lattice is disrupted, say by supplying (a lot of!) heat to give molten
This is due to the arrangement of ions...
In the solid state, the ions are held in fixed positions in a crystal lattice held together by strong electrostatic forces of attraction. Thus, there's no mobile charge carriers to conduct electricity.
In the molten state, the ions are free to move around to conduct electricity.