development of the periodic table By firstname.lastname@example.org Jan 25, 1829 law of trials prposed In 1829 Dobereiner proposed the Law of Triads: Middle element in the triad had atomic weight that was the average of the other two members. Jan 1, 1860 first 60 elements in 1860 the first 60 elements found Jan 1, 1862 the first periodic table had been published the first periodic table was made by proffesor Alexandre Beguyer de Chancourtois Jan 31, 1869 new arrangment of periodic table perposed Dimitri Mendeleev proposed arranging elements by atomic weights Jan 31, 1871 17 group table with eight columns In 1871 Mendeleev revised the 17-group table with eight columns (the eighth group consisted of transition elements). Jan 31, 1895 discoverd the inert gases In 1895 Rayleigh reported the discovery of a new gaseous element named argon. Jan 31, 1911 elements xrayed Soon after Rutherford's landmark experiment of discovering the proton in 1911, Henry Moseley subjected known elements to x-rays. Jan 31, 1940 last major change to the periodic table Starting with plutonium in 1940, Seaborg discovered transuranium elements 94 to 102 and reconfigured the periodic table by placing the lanthanide/actinide series at the bottom of the table. Jan 31, 1951 seaborg got a nobel prize In 1951 Seaborg was awarded the Nobel Prize in chemistry and element 106 was later named seaborgium (Sg) in his honor.