Atomic Theory

  • Dalton's Atomic Theory

    first atomic theory, first scientific evidence that the atom exists
  • James Clerk Maxwell

    Proposed electric and magnetic fields filled the void.
  • Cathode Ray Tube Experiments

    JJ Thompson discovered that an electrical current passed through gases at very low pressure in a glass tube. These experiments led to the discovery of the electron.
  • Plum Pudding Model

    JJ Thompson discovered a way to explain why most atoms are neutral.
  • Albert Einstein

    published the famous equation E=mc2
  • The Atomic Nucleus

    In Rutherford's Gold Foil Experiment, he discovered that fast moving alpha particles were shot at a thin piece of gold foil. Most went straight through the foil with only a slight deflection. He concluded that there was an existence of a very small, dense, positively, charged nucleus that contains most of the atom's mass, but occupies an insignificant fraction of it's volume.
  • Robert Millikan

    Oil drop experiment determined the charge (e=1.602x10-19 coulomb) and the mass (m=9.11x10-28 gram) of an electron.
  • Ernest Rutherford

    Using alpha particles as atomic bullets, probed the atoms in a piece of thin (0.00006 cm) gold foil . He established that the nucleus was: very dense,very small and positively charged. He also assumed that the electrons were located outside the nucleus.
  • Composition of the Nucleus

    Rutherford, "the proton"- a positive charge equal in magnitude to the negative charge of an electron and about the same mass as a neutron.
  • Niels 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.
  • de Broglie

    Discovered that electrons had a dual nature- similar to both particles and waves. Particle/wave duality. Supported Einstein.
  • Werner Heisenberg

    Proposed Principle of Indeterminancy - you can not know both the position and velocity of a particle.
  • Erwin Schrodinger

    Viewed electrons as continuous clouds and introduced "wave mechanics" as a mathematical model of the atom.
  • Composition of the Nucleus

    The Neutron: (Chadwick)- electically neutral, slightly heavier than a proton.
  • Enrico Fermi

    Conducted the first controlled chain reaction releasing energy from the atoms nucleus.