According to About.com, ionic substances conduct electricity when dissolved in water because the movement of their negatively and positively charged particles creates an electrical current. In this liquid condition, the charged ions split and travel freely, producing a stream of electrically conducting particles.
Electrical conductivity assesses a substance’s ability to produce an electrical current, whereas electricity is the movement of charged particles that comprise that current. In the field of electricity, a current is essentially a flow of charges that demands free movement. The formation of an electrical current requires both motion and conductivity.
When positively and negatively charged ions establish strong bonds, ionic compounds are created. These ions are atoms that have received or lost an electron, and they join through a process known as ionic bonding, which involves the transfer of an electron. A cation is a positively-charged ion, while an anion is a negatively-charged ion. Sodium Chloride, NaCl, is an example of an ionic compound in which Sodium (NA) is the cation and Chlorine (Cl) is the anion.
Solid ionic compounds have particles that are packed securely together, inhibiting movement and preventing the formation of electrical current. Consequently, ionic solids are not electrically conductive. The ionic link is broken when a substance is dissolved in water, allowing the charged ions to split and flow freely. The water facilitates particle mobility, while the separated ions give conductivity. Because both components are present, an electrical current is generated to conduct electricity.