Democritus (460-370 BCE)
A Greek philosopher who developed a theory (atomism) that suggested that all phenomena are to be explained by the incessant movement of atoms, differing only in shape, order, and position.
- He believed that the hard atoms of the four primitive elements (earth, air, water, and fire) moved in a vacuum. The shape and size of these atoms explained some of their properties. For example, the atoms of fire were tiny spheres which, because of their smooth surfaces, did not link with the atoms of the other elements. The atoms of earth, air, and water had shapes which enabled them to connect with each other and form visible matter.
Source: Metcalfe, H. Clark, John E. Williams, and Joseph F. Castka 1974. Modern Chemistry. New York, NY. Holt, Rinehart and Winston