Atomic Structure Timeline

By alannamao
  • 460

    Democritius

    Democritius
    Matter is made of small indivisible particles which have different form, position, and arrangement.

  • Newton

    Newton
    The universe is a mechanical universe with small solid masses in constant motion.

  • Dalton

    Dalton
    Spherical atoms have measureable properties of mass

  • G.J Stoney

    G.J Stoney
    Proposed that electricity was made of discrete negative particles, called electrons.

  • J.J Thompson

    J.J Thompson
    Discovered the electron and used cathode ray tubes to determine the charge to mass ratio of an electron to be 1.759 x 108 coulombs/ gram. He also found canal rays were associated with a proton.

  • Planck

    Planck
    Used quanta, discrete units of energy to explain glowing hot matter.

  • Nagaoka

    Nagaoka
    There are flat rings of electrons revolving around a positively charged particle.

  • Milikan

    Milikan
    Determined the charge and the mass of an electron to be 1.602 x 10-19 C and 9.11 x 10-28 g respectively.

  • E. Rutherford

    E. Rutherford
    Determined that the nucleus is a small, dense, positively charged part of the atom.

  • H.G.J Mosely

    H.G.J Mosely
    Stated that the atomic number is equal to the number of protons in the nucleus.

  • Bohr

    Bohr
    Created a model of successful orbital electron shells.

  • James Chadwick

    James Chadwick
    Discovered the neutron by using alpha particles.