Periodic Table By Gunn Jan 1, 1860 Stanislao identified that elements can have more than one atom Period: Jan 1, 1860 to Feb 15, 2015 Periodic Table Jan 1, 1864 Dimitri creates a table based on atomic weights. Jan 1, 1869 Dimitri devises the periodic table. Jan 1, 1894 The term nobel gasses was discovered. Jan 1, 1895 X-Ray beams were discovered. Jan 1, 1898 Marie finds two new elements "Polonium" and "Radium." Jan 1, 1905 Half-Life term was invented. Jan 1, 1940 Neptunium is identified.
