An atom is the smallest unit of matter that is recognizable as a chemical ELEMENT. Atoms of different elements may also combine into systems called MOLECULES, which are the smallest units of chemical COMPOUNDS. In all these ordinary processes, atoms may be considered as the ancient Greeks imagined them to be: the ultimate building blocks of matter. When stronger forces are applied to atoms, however, the atoms may break up into smaller parts. Thus atoms …showed first 75 words of 3821 total…

…showed last 75 words of 3821 total…into a heavier nucleus that can be studied for a short time before it disintegrates. Such heavy-ion collisions have produced nuclei that contain as many as 300 nucleons. Gerald Feinberg Bibliography: Beyer, Robert, ed., Foundations of Nuclear Physics (1949); Feinberg, Gerald, What is the World Made Of? (1977); Lapp, Ralph, and Andrews, Howard, Nuclear Radiation Physics (1972); Pais, Abraham, Inward Bound (1986); Van Melsen, Andrew, From Atomos to Atom (1952); Whittaker, Edmund, A History of the Theories of Aether and Electricity (1960).