History of A Timeline

  • John Dalton

    John Dalton gave us our first true model of an atom, and even expanded that to an atomic theory. In 1808 , Dalton published a paper that for the first time began to explain the behavior of chemicals.
  • J.J Thomson

    First scientist that decided that dalton's atom needed to be updated , so he proppsed a new model of the atom.His model became known as the plum pudding model
  • Max Planck

    used the idea of quanta (discrete units of energy) to explain hot glowing matter.
  • Robert Millikan

    Oil drop experiment determined the charge (e=1.602 x 10 -19 coulomb) and the mass (m = 9.11 x 10 -28 gram) of an electron.
  • Marie & Pierre Curie

    She and her husband Pierre also discovered the radioactive elements polonium and radium.
  • Ernest Rutherford

    Rutherford's planet system modl was an improvement over earilker models but it was still not complete.
    he proposed that all the postive charge is concentrated in a small core in the center of a atom
  • Werner Heisenberg

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

    Niels Bohr
    proposed a new model that would aloow the electrons to be outside the nucleus and in orbit around the nucleus. his model coupled rutherfords model with a newer concept regarding energy called quantum mechanics
  • Henri Becquerel

    The materialBecquerel was a double sulfate of uranium and potassium which he exposed to sunlight and placed on photographic plates wrapped in black paper.When developed, the plates revealed an image of the uranium crystals.