Scientists Contribution to Atomic Theory

  • 460


    According to Democritus' theory, atoms cannot be destroyed and they exist in a vacuum or void, which corresponds to the space between atoms. Atoms of a liquid are smooth and round; atoms of a solid are jagged and catch on to each other.
    Atoms differ only in shape, position, and arrangement
  • Newtown

    Proposed a mechanical universe with small solid masses in motion.
  • Dalton

    Proposed an "atomic theory" with spherical solid atoms based upon measurable properties of mass.
  • G.J. Stoney

    Proposed that electricity was made of discrete negative particles he called "electrons"
  • J.J. Thomson

    Used a CRT to experimentally determine the charge to mass ratio (e/m) of an electron =1.759 x 108 coulombs/gram.
  • Planck

    Used the idea of quanta (discrete units of energy) to explain hot glowing matter.
  • Nagaoka

    Postulated a "Saturnian" model of the atom with flat rings of electrons revolving around a positively charged particle.
  • Milikan

    He discovered that the weight of an electron is 1836 times smaller than that of a hydrogen atom (atomis mass of 1)
  • E. Rutherford

    He established that the nucleus was: very dense,very small and positively charged. He also assumed that the electrons were located outside the nucleus.
  • H.G.J. Mosely

    he sorted the chemical elements of the Periodic Table of the Elements in a quite logical order based on their physics.
  • Bohr

    Developed an explanation of atomic structure that underlies regularities of the periodic table of elements. His atomic model had atoms built up of sucessive orbital shells of electrons.
  • James Chadwick

    Using alpha particles discovered a neutral atomic particle with a mass close to a proton. Thus was discovered the neutron.