VIII.

Secret of the Chemical Bond

Much of the early knowledge of electricity emerged from discoveries in chemistry, specifically in what is now called electrochemistry. Volta’s battery taught scientists that an electrical current can flow around a circuit in a wire that reaches from one pole of the battery to the other. When the circuit is interrupted by wires attached to pieces of metal immersed in a liquid, the current flows through the liquid. The current in the liquid, they found, creates a chemical process called decomposition. If the liquid is water, hydrogen gas appears near one piece of metal, and oxygen near the other. The proportion of two parts hydrogen to one part oxygen indicated that water was being decomposed into its constituent elements, since a molecule of water is made up of two atoms of hydrogen and one atom of oxygen. Similarly, a solution of sodium chloride resulted in a plating of sodium on one terminal and the appearance of the greenish gas chlorine at the other.

The decomposition of chemical compounds by an electrical current indicated a profound connection between electricity and the way atoms bind to each other. This connection led to the theory that the attractions between atoms—that is, the affinity one chemical has for another—were electrical in nature.