Atomic theory By ava3a Period: 800 BCE to 2021 Atomic theory 460 BCE Empedocles and the Aristoleian elements 440 BCE Leucippus and atomism 420 BCE Democritus and the atom 360 BCE Aristotle and the Aristoleian elements 1660 Isaac Newton begins to understand that atoms are always in motion. 1662 Robert Boyle publishes Boyle's Law. 1770 Antoine Lavoisier discovers the law of conservation of mass. 1794 Joseph Proust publishes Proust's Law. 1802 John Dalton publishes his atomic theory. 1808 Jons Jacob Berzelius creates the nomenclature of elements and establishes the atomic weight of elements. 1811 Amedeo Avogadro publishes his molecular hypothesis. 1815 William Prout publishes his hypothesis on atomic weight. 1821 Michael Faraday publishes Faraday's laws. 1827 Robert Brown discovers the first accepted evidence that atoms exist. 1858 Julius Plucker discovers first real evidence of electron. 1858 Stanislao Cannizzaro publishes "Sunto de un corso di filosofia chimica”. 1861 Sir William Crookes discovers thallium and creates the Crookes radiometer. 1864 John Newlands publishes his law of octaves. 1869 Dmitri Mendeleev creates his periodic table of the elements. 1873 Sir William Crookes discovers the atomic weight of thallium. 1874 G.J. Stoney first uses the term "electron". 1886 Eugen Goldstein discovers the proton. 1895 W.K. Roentgen discovers x-rays. 1895 Jean Baptiste Perrin proves that cathode rays carry negative charges and are particles. 1896 J.J. Thomson discovers the electron. 1896 Henri Becquerel works on uranium and discovers Becquerel Rays. 1897 Lord Kelvin creates the plum pudding model of the atom. 1897 Marie and Pierre Curie discover polonium and curium. 1900 Max Planck creates quantum theory and Planck's constant. 1904 Hantaro Nagaoka publishes his Saturnian system model of the atom. 1905 Albert Einstein proves the existence of atoms. 1908 Hans Geiger creates the geiger counter. 1908 Geiger, Marsden, and Rutherford conduct the gold foil experiments. 1908-1913 1908 Jean Baptiste Perrin confirms the atomic nature of matter. 1909 Robert Millikan discovers the charge of an electron. 1911 Ernest Rutherford publishes his nucleus theory. 1911 Antonius van den Broek discovers alphon particles. 1913 Niels Bohr creates his model of the atom. 1913 Henry Moseley discovers the atomic number. 1913 Frederick Soddy discovers that not all radioactive preparations are unique elements. This is when he coined the term isotope. 1914 Henry Moseley publishes Moseley's law. 1919 Francis Aston creates the mass spectograph to map isotopes. 1922 Louis de Broglie publishes the de Broglie wavelength. 1926 Erwin Schrodinger formulates his wave equation and creates the quantum mechanical model. 1927 Werner Heisenberg discovers and publishes the uncertainty principle. 1932 James Chadwick proves the existence of neutrons. 1934 Enrico Fermi creates the first nuclear chain reaction. 1935 Frederic and Irene Joilot-Curie create the first artifical radioactive isotopes. 1938 Otto Hahn, Lise Meitner, and Fritz Strassman discover nuclear fission. 1941 Enrico Fermi helps to create the first nuclear reactor. 1941 Glenn Seaborg discovers plutonium-239. 1949 Maria Goeppert Mayer and Hans Jensen create the nuclear shell model. 1964 Murray Gell-Man and George Zweig discover quarks. Apr 26, 1986 Chernobyl Nuclear Powerplant meltsdown. Mar 11, 2010 Fukushima Daiichi nuclear disaster occurs.