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Proposed a mechanical universe with small solid masses in motion.
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Proposed an "atomic theory" with solid sphere atoms.
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Arranged known elements into groups with similar properties based on increasing mass (first periodic table).
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Discovers subatomic particles and develops the "Plum-Pudding Model".
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Discovered the charge and mass of an electron.
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Discovered the nucleus of the atom where protons and neutrons are contained.
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Proposed that electrons orbit the nucleus in defined energy levels.
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Reorganized the periodic table according to atomic number.
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Developed the Aufbau Principle within the electronic configuration of atoms.
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Wrote the Exclusion Principle for electrons in atoms.
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Developed the Uncertainty Principle (it is impossible to know both the position and velocity of an electron simultaneously).
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Discovered the neutron.