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Atomic Theory Timeline

By RandomAccountThatiWillNeverUseAgain
  • 460

    Democritus

    Democritus
    http://en.wikipedia.org/wiki/Democritus
    When:460 BC
    Where: Greece
    What: Democritus and Leucippus' theory stated that everything is composed of atoms, which are physically indivisible; between atoms, there lies empty space; atoms are indestructible; atoms have always been, and will always be in motion; and there are an infinite number of atoms, and kinds of atoms, which differ in shape and size.

  • Antoine Lavoisier

    Antoine Lavoisier
    http://en.wikipedia.org/wiki/Antoine_Lavoisier
    When: 1778
    Where: France
    What: Considered to be the father of chemistry, Antoine Lavoisier discovered oxygen in 1778, as well as discovering its role in combustion.

  • John Dalton

    John Dalton
    http://en.wikipedia.org/wiki/John_Dalton
    When: 1803
    Where: England
    What: John Dalton proposed the Atomic Theory. Which stated:
    1. All matter is made of atoms. Atoms are indivisible and indestructible.
    2. All atoms of a given element are identical in mass and properties.
    3. Compounds are formed by a combination of two or more different kinds of atoms.
    4. A chemical reaction is a rearrangement of atoms.

  • Dmitri Mendeleev

    Dmitri Mendeleev
    http://en.wikipedia.org/wiki/Dmitri_Mendeleevhttp://en.wikipedia.org/wiki/Dmitri_Mendeleev
    When: 1869
    Where: Russia
    What: Created the first version of The Periodic Table of Elements.

  • J.J. Thompson

    J.J. Thompson
    When: 1897
    Where: England
    What: Through his experiments with cathode ray tubes, he showed that cathode rays were composed of electrons, which is why he is credited with the discovery of electrons, and the discovery of the first subatomic particle

  • Robert A, Millikan

    Robert A, Millikan
    http://en.wikipedia.org/wiki/Robert_Andrews_Millikan
    When: 1909
    Where: U.S.
    What: Used the oil-drop experiment to measure the mass and charge of the electron.

  • James Chadwick

    James Chadwick
    http://en.wikipedia.org/wiki/James_Chadwick
    When: 1932
    Where: England
    What: Discovered the neutron in the atom's nucleus.

  • Niels Bohr

    Niels Bohr
    http://en.wikipedia.org/wiki/Niels_Bohr
    When: 1992
    Where: Denmark
    What: Suggested that electrons move in an orbit around the nucleus, and contributed the Bohr Planetary Model.