# Why is an ionic solid non-conductive, but conductive in aqueous solution?

Dec 4, 2016

The generic ionic solid is $M X$, and consists of equal number of ${M}^{+}$ and ${X}^{-}$ ions that are held together in a non-molecular, electrostatically bound lattice. The ions are not free to move in the solid state, and thus cannot carry a charge.
In certain circumstances, with certain solvents, for instance water, the ionic solid can dissolve to produce ${M}^{+} \left(a q\right)$ and ${X}^{-} \left(a q\right)$ ions that are free to move in solution. We write ${M}^{+} \left(a q\right)$ to represent the aquated ion, i.e. ${\left[M {\left(O {H}_{2}\right)}_{6}\right]}^{+}$ or something similar. And in solution these ions can carry a charge in that the ions are mobile.