Download (1)

History of the Atom

  • 460 BCE


    Democritus was a Greek philosopher who was the first to suggest the existence of atoms and also believed that they were indivisible and indestructible.
  • John Dalton

    John Dalton
    John Dalton was a British physicist who created the discovery of the electron.
    Daltons atomic theory
    1. All elements are composed of atoms
    2. Atoms of the same element are identical
    3. Atoms of different elements combine in simple whole-number ratios to form chemical compounds
    4. In chemical reactions, atoms are combined, separated, or rearranged but never change
  • Dmitri Mendeleev

    Dmitri Mendeleev
    A Russian chemist and inventor who formulated the periodic law and created a farsighted version of the periodic table of elements
  • Eugen Goldstein

    Eugen Goldstein
    Eugene Goldstein discovered the proton and positive particles by using a tube filled with hydrogen gas. This resulted in The positive particle had a charge equal and opposite to the electron. When an electron is removed from a hydrogen atom, a proton remains. Goldstein observed rays traveling in the opposite direction of the cathode rays in a cathode ray tube.
  • J.J. Thomson

    J.J. Thomson
    In 1897, J.J. Thomson used a Cathode ray tube to deduce the presence of negatively charged in the electron
    Thomson also created the "Plum Pudding" model
  • Max Planck

    Max Planck
    Planck's quantum theory was that different atoms and molecules can emit or absorb energy in discrete quantities only. The energy of the radiation absorbed or emitted is directly proportional to the frequency of the radiation.
  • Robert Millikan

    Robert Millikan
    Millikan discovered the accurate determination of the charge carried by an electron, using the elegant “falling-drop method". He also proved that this quantity was a constant for all electrons.
  • Niels Bohr

    Niels Bohr
    Niels Bohr proposed a theory for the hydrogen atom, based on quantum theory that some physical quantities only take discrete values. Electrons move around a nucleus, but only in prescribed orbits.
  • Ernest Rutherford

    Ernest Rutherford
    Ernest Rutherford was a New-Zealand born British physicist, who found out that most of the particles pass through gold foil when doing a Gold foil experiment and very few particles were deflected
  • Erwin Schrödinger

    Erwin Schrödinger
    Erwin Schrödinger showed that the quantization of the hydrogen atom's energy levels that appeared in Niels Bohr's atomic model could be calculated from the Schrödinger equation, which describes how the wave function of a quantum mechanical system evolves.
  • Werner Heisenberg

    Werner Heisenberg
    Werner Heisenberg contributed to atomic theory through formulating quantum mechanics in terms of matrices and in discovering the uncertainty principle, which states that a particle's position and momentum cannot both be known exactly.
  • James Chadwick

    James Chadwick
    James Chadwick was a British physicist who in fact discovered the neutron