Mendeleev’s Periodic Table did not include noble gases because at that time it was not discovered then. The English physicists John William Strutt and William Ramsay discovered four of the noble gases. Argon and helium were discovered by the two scientists in 1894. To fit argon and helium into the table, they proposed a new group that was placed between Group 17 and Group 1. Then, krypton and xenon were discovered by Ramsay in 1898. Radon, the final noble gas, was discovered in 1900 by a German scientist named Friedrich Ernst Dorn.
Glenn Seaborg was an American scientist and he discovered all the transuranic elements from 94 to 102. With this discovery, he was the last person to majorly change the Periodic Table by placing the actinide series below the lanthanide series.
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