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Proposed first idea of the atom: substances made up of tiny indestructible, indivisible particles called "atomos."
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He felt that regardless of the number of times you cut a form of matter in half, you would always have a smaller piece of that matter.
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Laid down the foundation of the modern day Periodic Table of the elements.
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Law of Conservation of Mass: matter cannot be created or destroyed, only rearranged.
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Law of Multiple Porportions: same two elements can combine in different compounds: ratio of first element is fixed, while the second element varies. Proposed the first Atomic Theory.
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Discovered cathode rays had the following properties: travel in straight lines from the cathode; cause glass to fluoresce; impart a negative charge to objects they strike; are deflected by electric fields and magnets to suggest a negative charge; cause pinwheels in their path to spin indicating they have mass.
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Discovered x-rays.
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Discovered that uranium ores emit radiation resembling x-rays and that it exposed film.
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Studied uranium and thorium and called their spontaneous decay process "radioactivity". They discovered the radioactive elements polonium and radium.
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Quantium Theory: energy is not emmited constantly, but in small packets called quantum.
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Developed an electrical device to "click" when hit with alpha particles.
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Performed oil drop experimant, which determined the charge of electrons as negative.
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Studied substances, especially alpha particles. Conducted gold foil experiment: he bombarded gold foil with alpha particles. Most particles passed through the foil but some were deflected. He concluded that the atom is mostlhy empty space, with a very small positive nucleus core.
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Improved upon the atomic model by trying to answer the question: why aren't electrons pulled into the nucleus?
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Viewed electrons as continuous clouds and introduced "wave mechanics" as a mathematical model of the atom.
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Discovered the neutron.
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Conducted experiments verifying that heavy elements capture neutrons and form unstable products which undergo fission. This process ejects more neutrons continuing the fission chain reaction.
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Synthesized 6 transuranium elements and suggested a change in the layout of the periodic table.
