Josh Huver Huver - 1 Mr. Billings Honors Chemistry 17 January, 2006 The Models Of The Atom In the 4 th and 5 th centuries B.C., a Greek Philosopher named Democritus suggested that all matter was composed of tiny indivisible particles called atoms In 1803, John Dalton theorized that atoms were tiny, indestructible particles with no internal structure. His atomic theory was based on 4 major points. 1) All elements are composed of tiny indivisible particles called atoms. 2) Atoms of the same element are identical. The atoms of any one element are different from those of any other element. 3) Atoms of different elements can physically mix together or can chemically combine in simple whole-number ratios to form compounds. 4) Chemical reactions occur when atoms are separated, joined, or rearranged. Atoms of one element, however, are never changed into atoms of another element as a result of a chemical reaction. In 1897, J.J. Thompson discovered the electron through experiments by sending electric currents
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