Color enhanced illustration of Dmitry Ivanovich Mendeleyev (1834-1907), Russian chemist. Mendeleyev (or Mendeleev) was initially an indifferent student, but left college at the top of his class. After attending the 1st Karlsruhe Congress (1860), Mendelayev worked on organizing trends in atomic weights and valency. From this, he developed the first true periodic table of the elements (final version published in 1871). This contained some gaps, but as new elements were discovered to have the properties predicted by the table, Mendeleyev became famous worldwide.