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Helped develop the definition of an element, also with the "death" of the four elements- Earth, Fire, Air, Water.
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Disocovered that water was made of Hydrogen and Oxygen. Also invented the analytical balanance and showed that chemical elements were neither created nor destroyed- Conservation of Mass
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Discovered Oxygen and identified Molybdenum, Tungsten, Barium, Hydrogen, Chlorine.
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Published Oxygen findings before Carl Scheele.
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Created Law of Definite Proportions and studied Copper Carbonate, 2 Tin Oxide, 2 Iron Sulfide.
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Created Modern Atomic Theory.
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Built the first Cathode Ray Tube.
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Discovered Cathode Ray's properties.
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Confirmed Einstein's ideas on Browmian motion by calcuating Avogadro's Constant, proving Dalton's Atomic Theory.
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Studied "canal rays" and found they were associated with the proton H+. Used a CRT to experimentally determine the charge to mass ratio of an electron.
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Studied Uranium and Thorium and called their spontaneous decay process "radioactivity". Also discovered radioactive elements Polonium and Radium.
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Studied radiations emitted from Uranium and Thorium and named them Alpha and Beta.
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Observed spontaneous disintegration of radioactive elements into variants he called "isotopes" or totally new elements. Discovered "half life", made initial calculations on energy released during decay.
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Developed an electrical device to "click" when hit with Alpha particles.
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Measured the charge of an electron with his oil-drop apparatus. He proved Thomson's hypothesis that the mass of an electron is at least 1000 times smaller than the smallest atom.
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Discovered structure of an atom with the "gold foi" experiment.
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Using alpha particles discovered a neutral atomic particle with a mass of a proton- Neutron.