Chemical Bond

The concept of bonding as a force that holds two particles together is as old as the concept of ultimate particles of matter itself. As early as 100 B.C., for example, Asklepiades of Prusa speculated about the existence of "clusters of atoms," a concept that implies the existence of some force of attraction holding the particles together. At about the same time, the Roman poet Lucretius in his monumental work De Rerum Natura ("On the nature of things") pictured atoms as tiny spheres to which were attached fishhook-like appendages. Atoms combined with each other, according to Lucretius, when the appendages from two adjacent atoms became entangled with each other.

Relatively little progress could occur in the field of bonding theory, of course, until the concept of an atom itself was clarified. When John Dalton proposed the modern atomic theory in 1803, he specifically hypothesized that atoms would combine with each other to form "compound atoms." Dalton's concept of bonding was essentially non-existent, however, and he imagined that atoms simply sit adjacent to each other in their compound form.

The real impetus to further speculation about bonding was provided by the evolution of the concept of a molecule, originally proposed by Amedeo Avogadro in 1811 and later refined by Stanislao Cannizzaro more than four decades later.