Electrolysis

By electrolysis, common salt, sodium chloride, NaCl, can be broken down into its elements, sodium and chlorine. This is an important method for the production of sodium; it is used also for producing other alkali metals and alkaline earth metals from their salts.

To obtain sodium by electrolysis, we will first melt some sodium chloride by heating it above its melting point of 1,474°F (801°C). Then we will insert two inert (non-reacting) electrodes into the melted salt. The sodium chloride must be molten in order to permit the Na⁺ and Cl^- ions to move freely between the electrodes; in solid sodium chloride, the ions are frozen in place. Finally, we will pass a direct electric current (DC) through the molten salt.

The negative electrode (the cathode) will attract Na⁺ ions and the positive electrode (the anode) will attract Cl^-ions, whereupon the following chemical reactions take place.

At the cathode, where electrons are being pumped in, they are being grabbed by the positive sodium ions:

At the anode, where electrons are being pumped out, they are being ripped off the chloride ions:

(The chlorine atoms immediately combine into diatomic molecules, Cl₂.) The result is that common salt has been broken down into its elements by electricity.