Atomic Theory By laurenanderin 460 Democritus- discovery of atoms BC Period: 460 to Jan 1, 2000 Atomic Theory Jan 1, 1789 Antoine Lavoisier- Law Of Conservation of Mass Jan 1, 1803 Dalton's Atomic Theory Jan 1, 1869 Dmitri Mendeleev- First Periodic Table Jan 1, 1909 Robery A. Millikan-electronic charge Jan 1, 1911 Ernest Rutherford- Rutherford Model/ Gold Foil Experiment Jan 1, 1912 J.J. Thomson- Cathode Ray Tube/ Plum Pudding Atomic Model Jan 1, 1913 Henry Moseley- X-Ray Spectra Jan 1, 1922 Niels Bohr- Bohr Planetary Model Jan 1, 1926 Erwin Schrodinger- Quantum Mechanical Model/ Electron Cloud Model Jan 1, 1932 James Chadwick-Existence of Neutrons