Electrical currents of any description require two properties. There must be a charged particle and that particle must be free to move about. In metals, the charged particles are the electrons in the electron pool. Since they are no longer bound to a particular nucleus, they may drift under the influence of an electric potential. There are no free electrons in either ions or molecules. These two substances are poor electrical conductors in the solid state.

When melted or dissolved, however, the individualions in an ionic compound are able to break away from each other and their position in the crystal (lattice) and can drift. And since both anionsand cations are charged particles, molten or dissolved ionic substances do tend to be electrical conductors. Most molecules fail to conduct electricity in solid, liquid or gaseous states, or in solution, under normal circumstances.(You don’t want to be in the room when the testing to determine conductivity of gases starts.)

For more about conductivity, go to the page on elecrical resistance. Resistance is literally the inverse of conductivity. Hi conductivity means low resistance and vice versa.
 

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