He left empty boxes in his 1869 table — and the missing elements showed up on schedule.
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.
Mendeleev was born in 1834 in Tobolsk, Siberia, the youngest of a large family; his mother ran a glass factory to support them. He studied in St. Petersburg, then in Heidelberg, Germany, and returned to become professor of chemistry at St. Petersburg University.
Writing his 'Principles of Chemistry' textbook in the late 1860s, he needed a logical order for the elements — and began writing each element's weight and properties on cards, dealing them out on his desk looking for the pattern.
On March 6, 1869, he presented the table to the Russian Chemical Society: elements ordered by atomic weight, arranged so that elements with similar properties fell in the same columns — periodicity. Where the pattern demanded an element that did not exist, he left a gap and predicted its weight, density and chemistry.
He called them eka-aluminium and eka-silicon. In 1875 the Frenchman Lecoq de Boisbaudran discovered gallium — matching the prediction; in 1886 the German Clemens Winkler found germanium — matching again. The table had foretold nature.
Others had glimpsed periodicity — the German Lothar Meyer published a similar table in 1870 — but Mendeleev's predictions made his version the one that stuck. Rearranged by atomic number in the 20th century, it hangs in every chemistry classroom on earth.
Element 101, synthesized in 1955, was named mendelevium in his honor — the only element named for its table's creator. Nominated for the Nobel Prize, he never received it; the table outlasted the slight.
