Why cannot solid ionic compounds conduct electricity?

Solid ionic compounds cannot conduct electricity because they do not contain free mobile ions or electrons. In a solid state, the ions within the ionic compound are locked in a rigid lattice structure. This arrangement prevents the ions from moving freely. Conductivity in materials generally requires the presence of charged particles that can move, allowing for the flow of electricity. In the case of solid ionic compounds, although they are composed of charged ions, the lack of mobility within the solid structure means that electrical conductivity is not possible.

When solid ionic compounds are dissolved in water or melted, the rigid lattice breaks down, freeing the ions. In these conditions, the ions can move independently and carry electric current, which is why ionic compounds are good conductors of electricity in their liquid form or when dissolved in solution.