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Democritus (460-370 B.C.):
He was the first person to suggest that matter could not be infinitely divided. He came up with the name "atomos" to describe the particles that cannot be created or destroyed. -
Aristole (384-322 B.C.): He completely diagreed with Demitus' idea that atoms moved through space. He completely denied the existence of atoms altogether.
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John Dalton (1766-1844): He marked the beginning of the development of modern atomic theory. He revised the ideas of Democritus. He came to the conclusion that atoms were the smalled form of matter.
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Sir William Crooks (1832-1919): He led scientists to to the the idea that cathode rays were a stream of charged particles adn that the particles carried a negative charge (electrons)
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J.J. Thompson (1856-1940): He determined the ratio of a particle's charge to its mass. COncluded that the mass of the particle was much less than that of the Hydrogen atom.
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Ernest Rutherford (1871-1937): Studied how positively charged atoms interact with solid matter. He designed an experiment to see if a particles would be deflected as they passed through a thin sheet of gold foil.
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Robert Milikan (1868-1953) He designed an oil drop apparatus to determine the charge of the elctron. He determined that the magnitude of the charge of the electron was 1.602*10^-19 coulombs. He also discovered the mass of the electron using the known charge/mass ratio: 9.1*10^-28*g
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James Chadwick (1891-1974): He demonstrated that the nucleus had another neutral subatomic particle, the neutron.
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