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The Greek philosopher, Democritus began to believe that all matter is composed by indivisible elements.
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Issac Newton theorized that there is an invisible microscopic mechanical universe with small, solid masses in motion.
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Scientist, John Dalton, proposed that elements contain atoms that are identicle and have the same mass. Compounds were atoms from different elements combined.
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Michael Faraday developed the two laws of electrochemistry.
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J. Pucker built one of the first cathode-ray tubes.
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Dmitiri Mendeleev created the first design of the Periodic Table.
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G.J. Stoney theorized that electricity was comprised of negative particles, which he called Atoms.
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Sir William Crookes' experiements with the cathode-rays tubes which led him to comfirm the work of eariler scientists by demonstrating that cathode-rays have a negative charge.
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E. Goldstein discovered canal rays, which have a positive charge equal to an electron.
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Wilhelm Roentgen discovered x-rays.
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Henri Becquerel discovered radiation by studying the effects of x-rays on photographic film.
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J.J. Thomson determined the charge to mass ratio of ratios.
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Rutherford discovered alpha, beta and gamma rays in radiation.
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Marie Sklodowska Curie discovered radium and polonium and coined the term radioactivity after studying the decay process of uranium and thorium.
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Max Planck proposed the idea of quantization to explain how a hot, glowing object emitted light.
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Fredrick Soddy came up with the term "isotope" to explain the unintentional breakdown of radioactive elements.
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Hantaro Nagaoka proposed atomic model called the Saturnian Model to describe the structure of an atom.
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Richard Abegg found that inert gases have a 'stable electron configuration.'
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Hans Geiger invented a device that could detect alpha particles.
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H.G.J. Moseley discovered that the number of protons in an element which determines its atomic number.
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Francis William Aston used a mass spectrograph to identify 212 isotopes.
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Niels Bohr proposed an atomic structure theory that stated the outer orbit of an atom could hold more electrons than the inner orbit.
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Louis de Broflie proposed that electrons have a wave/particle duality.
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Cockcroft / Walton created the first nuclear reaction, producing alpha particles.
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Paul Dirac proposed the existence of anti-particles.
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James Chadwick discovered neutrons, particles whose mass was close to that of a proton.
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Lise Meitner, Hahn, Strassman discovered nuclear fission.
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Glenn Seaborg discovered eight transuranium elements.
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Enrico Fermi created the first man-made nuclear reactor.