The term chemical bond refers to any force of attraction between two atoms or ions. Today, chemists recognize the existence of at least four types of chemical bonds: ionic (electrovalent), covalent, metallic, and hydrogen.

The concept of chemical bonds goes back—at least in its simplest and most general form--to the ancient Greeks. Philosophers who thought of matter as being composed of individual particles often considered the possibility that those particles might join, or bond with, each other in some way. As early as 100 b.c. Asklepiades of Prusa introduced the concept of "clusters" of atoms, somewhat similar to those that make up a molecule.

In 1789 the English chemist William Higgins (1763-1825) speculated about the way in which the fundamental particles of matter might combine with each other. When John Dalton proposed his atomic theory around 1803, he specifically hypothesized that the atoms of elements would...