Evolution of the Atom

  • Isaac Newton

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

    Proposed an "atomic theory" with solid sphere atoms.
  • Dmitri Mendeleev

    Arranged known elements into groups with similar properties based on increasing mass (first periodic table).
  • JJ Thomson

    Discovers subatomic particles and develops the "Plum-Pudding Model".
  • Robert Millikan

    Discovered the charge and mass of an electron.
  • Ernst Rutherford

    Discovered the nucleus of the atom where protons and neutrons are contained.
  • Niels Bohr

    Proposed that electrons orbit the nucleus in defined energy levels.
  • Moseley

    Reorganized the periodic table according to atomic number.
  • Niels Bohr

    Developed the Aufbau Principle within the electronic configuration of atoms.
  • Pauli

    Wrote the Exclusion Principle for electrons in atoms.
  • Heisenberg

    Developed the Uncertainty Principle (it is impossible to know both the position and velocity of an electron simultaneously).
  • James Chadwick

    Discovered the neutron.