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Atomic Theory

By cdh473
  • 460

    Democritus

    Democritus
    *Note: Year is in BCE.
    Theorized that everything was made of "atoms," little particles of matter that are and always were in motion and indestructible. Little did the cheeky swankswinger know that we would come to break those indestructible nanobehemoths.

  • Isaac Newton

    Isaac Newton
    Sir Isaac Newton proposed a mechanical universe with small solid masses in motion.

  • John Dalton

    John Dalton
    John Dalton came up with the idea of the "atomic theory," in which spherical, solid atoms are based on measurable attributes of mass.

  • Dmitri Mendeleev

    Dmitri Mendeleev
    Mendeleev grouped elements into 7 groups, categorizing them based on similar properties. He also created the Periodic Law (properties of elements are periodic functions of their atomic weights).

  • J. J. Thomson

    J. J. Thomson
    Discovered the electron and found the charge:mass ratio of the electron.

  • Marie Curie

    Marie Curie
    Studied radioactivity in uranium/thorium. Along with her husband, discovered polonium & radium.

  • R. A. Millikan

    R. A. Millikan
    Conducted the oil drop experiment to determine the charge and mass of an electron.

  • Ernest Rutherford

    Ernest Rutherford
    Rutherford was the first person to deliberately transmute one element to another. While working with Niels Bohr, he came up with the idea of neutrons existing as parts of atoms.

  • Lise Meitner

    Lise Meitner
    Discovered that heavier elements trap neutrons and create unstable byproducts that go through nuclear fission.

  • Hans Geiger

    Hans Geiger
    Along with Meitner, did experiments indicating that heavy elements capture neutrons, resulting in fission.

  • Niels Bohr

    Niels Bohr
    Applied quantum theory to the atomic structure, stating that electrons travel in stationary orbits, which are defined by their angular momentum.

  • H.G. Moseley

    H.G. Moseley
    Measured the wavelengths of x-rays, ultimately determining that the Periodic Law should not be based mostly upon atomic weight.

  • James Chadwick

    James Chadwick
    First to discover the neutron, even though this discovery was predicted by Ettore Majorana. Chadwick's discovery played a large role in the ability to produce heavier elements than was previously possible, as well as coming to understand much of nuclear fission.

  • Heisenberg

    Heisenberg
    Heisenberg created the Uncertainty Principle, which states that the exact location and energy of an electron can not be measured at the same time.