Mendeleev's periodic table predicted three elements nobody had yet found
Dmitri Mendeleev did more than tidy the known elements into rows. His periodic law let him correct uranium's atomic weight and forecast the properties of gallium, germanium and scandium before anyone discovered them. He later claimed the whole arrangement came to him in a dream.
Mendeleev was born in 1834 in Verkhnie Aremzyani, near Tobolsk in Siberia, the youngest of a very large family whose exact size is still disputed. His grandfather was a priest, and his father received the surname Mendeleev at seminary, borrowed from a local landowner. When his father went blind and lost his teaching post, his mother revived her family's abandoned glass factory. After his father died and the factory burned, she took the teenager across Russia in 1849. Moscow University turned him away, so they pressed on to the capital, and in 1850 he won a place at its Main Pedagogical Institute.
Tuberculosis sent him to Crimea in 1855, where he taught science in Simferopol before returning healthy in 1857. He studied capillarity and the spectroscope in Heidelberg, won the Demidov Prize for an organic chemistry textbook in 1861, and earned his doctorate in 1865 with a thesis on combining water with alcohol. By 1871 he had made Saint Petersburg a respected centre of chemical research. He also co-founded the Russian Chemical Society in 1868.
Others had spotted patterns before him. In 1863 chemists knew 56 elements, with roughly one more found each year. John Newlands proposed a Law of Octaves in 1864 and was ridiculed, gaining recognition only in 1887, while Lothar Meyer arranged 28 elements by valence without predicting any new ones. Mendeleev, unaware of this work, was writing his textbook Principles of Chemistry, published in two volumes from 1868 to 1870, when he began grouping elements by their chemistry.
On 6 March 1869 he presented his scheme to the Russian Chemical Society, arguing that properties repeat when elements are ordered by atomic weight and that similar elements have either close weights or weights rising in regular steps. The synthetic element mendelevium now bears his name. He also wrote on agriculture and protectionist trade, and his son reported that he drifted from Orthodoxy toward a romantic deism. He died in 1907.
Source: Dmitri Mendeleev
