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Democritus’ atomic theory posited that all matter is made up small indestructible units he called atoms.
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Isaac Newton theorized a mechanical universe with small, solid masses in motion.
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John Dalton proposed that elements consisted of atoms that were identical and had the same mass and that compounds were atoms from different elements combined together.
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Michael Faraday developed the two laws of electro-chemistry.
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J. Plucker built one of the first cathode-ray tubes.
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Dmitri Mendeleev created the periodic table.
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James Clerk Maxwell proposed the theory of electromagnetism and made the connection between light and electromagnetic waves.
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G.J. Stoney theorized that electricity was comprised of negative particles he called electrons.
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Sir William Crookes’ experiments with cathode-ray tubes led him to confirm the work of earlier scientists by definitively 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 electrons.
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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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Frederick Soddy came up with the term "isotope" to explain the unintentional breakdown of radioactive elements.
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Hantaro Nagaoka proposed an 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 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 Broglie 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.