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That all matter is made up small indestructible units he called atoms.
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Theorized a mechanical universe with small, solid masses in motion.
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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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Built one of the first cathode-ray tubes.
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Created the periodic table.
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Theorized that electricity was comprised of negative particles he called electrons.
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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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Discoered canal rays, which have a positive charge equal to an electron.
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Determined the charge to mass ratio of electrons.
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Discovered radium and polonium and coined the term radioactivity after studying the decay process of uranium and thorium
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Ccame up with the term "isotope" to explain the unintentional breakdown of radioactive elements
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Proposed an atomic model called the Saturnian Model to describe the structure of an atom.
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Invented a device that could detect alpha particles.
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Discovered that the number of protons in an element determines its atomic number.
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Uused a mass spectrograph to identify 212 isotopes.
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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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Proposed that electrons have a wave/particle duality.
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Created the first nuclear reaction, producing alpha particles
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Discovered neutrons, particles whose mass was close to that of a proton.
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Discovered nuclear fission
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Discovered eight transuranium elements.
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Created the first man-made nuclear reactor.
