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Aristotle – 350 BC – opposed the idea of “atomos”/an atom; believed that only four elements existed: Water, Earth, Fire, Air
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Democritus – 400 BC – first proposed the existence of “atomos” - an indivisible particle
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Dalton – 1803 – proposed the Atomic Theory
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Curie – 1898 – explored radioactivity which later contributed to the atomic model
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Thomson – 1904 – discovered the electron
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Einstein – 1905 – proved the existence of atoms and introduced relativity
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Millikan – 1909 – proved that the electron was 1000 times smaller than the atom
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Ernest Rutherford – 1910 – proposed existence of the nucleus with his Gold Foil Experiment
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Niels Bohr – 1913 – proposed electron energy levels and orbits
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De Broglie – 1924 – postulated the wave nature of electrons and suggested that all matter has wave properties.
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Schrodinger – 1926 – explained movement of an electron in an atom as a wave
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Heisenberg – 1926 – developed the fundamental principle on which quantum mechanics is based on
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Chadwick – 1932 – discovers neutrons
