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100
Democritus
about 400 B.C. he was the first man to suggest that all matter was made of small pieces -
J. J. Thomson
in the late 1890s he discovered that atoms are divisble into smaller particles -
Robert Milkkan
determined the mass of the elctron is 1/1840 the mass of a hydrogen atom -
gold foil experiment
Ernest Rutherford discovered the proton -
Ersnest Rutherford
he dicovered the proton and concluded that the nucleus was made up of positiviely charged particles -
James Chadwick
discovered the neutron and that it has no charge, and is found in the nucleus
