atomic theory(redirected from Atom theory)
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that chemical compounds are formed by the union of atoms in certain definite proportions; in its modern form, first advanced in 1803 by John Dalton.
Etymology: Gk, atmos, indivisible, theoria, speculation
the concept that all matter is composed of submicroscopic atoms that are in turn composed of protons, electrons, and neutrons. A chemical element is identified by the number of protons in its atoms.
1. The theory that all matter is composed of atoms.
2. Theories pert. to the structure, properties, and behavior of the atom.
See also: theory