Dmitri Mendeleev (1834–1907) was the Russian chemist who created the periodic table: in March 1869 he arranged the 63 known elements by atomic weight and chemical properties, left gaps for elements not yet discovered — and correctly predicted the properties of gallium and germanium years before they were found.
A professor in St. Petersburg writing a chemistry textbook, he said the pattern came to him after days of arranging element cards like a card game. Whether by dream or by deduction, the table he published ordered chemistry itself.
