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Atom Timeline

  • Period: 494 BCE to 404 BCE

    Democritus

    Came up with the idea of two things in the universe: atoms and voids. Atoms were solid and infinite in number and shape and differing in size. All atoms were floating around the infinite void.
  • Period: to

    J.J. Thomson

    1904 suggested model was a sphere of positive matter where electrons were positioned by electrostatic forces. Worked to estimate the number of electrons in an atom.
  • Period: to

    Ernest Rutherford

    Discovered that atoms have a small charged nucleus surrounded by lots of empty space, circled by tiny electrons. Credited with the discovery of the proton in 1919 and hypothesized the existence of the neutron.

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