6th period, Atomic Theory Timeline Rebecca S. and Brittany E. By sala3197 300 Democritus Jan 1, 1779 Antoine Lavoiser Jan 1, 1789 Law of Conservation of Mass Jan 1, 1803 John Dalton Jan 1, 1803 Daltons Atomic Theory Jan 1, 1869 Dmitri Mendeleev Jan 1, 1879 Cathode Ray Tube Jan 1, 1897 Plum Pudding Atomic Model Jan 1, 1897 J.J Thomson Jan 1, 1909 Robert Milikan Oct 31, 1911 Rutherford Model Oct 31, 1913 Henry Mosely Oct 31, 1922 The Bohr Planetary Oct 31, 1922 Niels Bohr Jan 1, 1926 Ernest Rutherford Jan 1, 1926 Gold Foil Experiment Oct 31, 1926 Erwin Schrodinger Oct 31, 1926 Quantum Mechanical Model Oct 31, 1932 James Chadwick Oct 31, 1935 Electron Cloud Model