Mendeleyev, Dmitri Ivanovich (1834-1907) was a Russian chemist whose name will always be linked with his outstanding achievement, the development of the Periodic Table. He was the first chemist to understand that all elements are related members of a single ordered system. He converted what had hitherto been a highly fragmented and speculative branch of chemistry into a true, logical science. The spelling of his name has been a source of confusion to students and frustration to editors for more than a century, and the forms Mendeléeff, Mendeléev and even Mendelejeff can all also be found in print. Mendeleyev was born in Tobol'sk, Siberia, on 7 February 1834, the youngest of the 17 children of the head of the local high school. His father went blind when Mendeleyev was still a child, and the family had to rely increasingly on their mother for support. He was educated locally but could not gain admission to any Russian university (despite his mother's attempts on his behalf with the authorities at Moscow) because of the supposedly backward attainments of those educated in the provinces. In 1855 he finally qualified as a teacher at the Pedagogical Institute in St Petersburg. He took an advanced degree course in chemistry, and in 1857 obtained his first university appointment. In 1859 he was sent by the government for further study at the University of Heidelberg where he made valuable contact with the Italian chemist Stanislao Cannizzaro, whose insistence on a proper distinction between atomic and molecular weights influenced Mendeleyev greatly. In 1861 he returned to St Petersburg and became Professor of General Chemistry at the Technical Institute there in 1864. He could find no textbook adequate for his students' needs and so he decided to produce his own. The resulting Principles of Chemistry (1868-1870) won him international renown; it was translated into English in 1891 and 1897. Mendeleyev began work on his periodic law in the late 1860s, and he went on to conduct research in various other fields. Then in 1890 he chose to be a spokesman for students who were protesting against unjust conditions. For these allegedly improper activities he was retired from the university and became controller of the Bureau for Weights and Measures, although from 1893 he received no other professorial appointment. He died in St Petersburg on 2 February 1907, five days before his seventy-third birthday. His nomination for the 1906 Nobel Prize in Chemistry failed by one vote (the award went to Henri Moissan) but his name became recorded in perpetuity 50 years later when element number 101 was called mendelevium. Before Mendeleyev produced his periodic law, understanding of the chemical elements had long been an elusive and frustrating task. The attempts by various chemists to put the whole field into some intelligible reference system had acted rather like the progressively stronger lenses of a microscope in bringing a sensed but unseen object into clear vision. According to Mendeleyev the properties of the elements, as well as those of their compounds, are periodic functions of their atomic weights (relative atomic masses). In 1869 he stated that 'the elements arranged according to the magnitude of atomic weights show a periodic change of properties'. Other chemists, notably Lothar Meyer in Germany, had meanwhile come to similar conclusions, Meyer publishing his findings independently. Mendeleyev compiled the first true Periodic Table, listing all the 63 elements then known. Not all elements would 'fit' properly using the atomic weights of the time, so he altered indium from 76 to 114 (modern value 114.8) and beryllium from 13.8 to 9.2 (modern value 9.013). In 1871 he produced a revisionary paper showing the correct repositioning of 17 elements. Also in order to make the table work Mendeleyev had to leave gaps, and he predicted that further elements would eventually be discovered to fill them. These predictions provided the strongest endorsement of the periodic law. Three were discovered in Mendeleyev's lifetime: gallium (1871), scandium (1879) and germanium (1886), all with properties that tallied closely with those he had assigned to them. Far-sighted though Mendeleyev was, he had no notion that the periodic recurrences of similar properties in the list of elements reflect anything in the structures of their atoms. It was not until the 1920s that it was realized that the key parameter in the periodic system is not the atomic weight but the atomic number of the elements - a measure of the number of nuclear protons or electrons in the stable atom. Since then great progress has been made in explaining the periodic law in terms of the electronic structures of atoms and molecules. Among Mendeleyev's other investigations were the specific volumes of gases and the conditions that are necessary for their liquefaction. Following visits to the oilfields of the Caucasus and in the United States he examined the origins of petroleum. He was convinced that the future held great possibilities for human flight, and in 1887 he made an ascent in a balloon to observe an eclipse of the Sun. He farmed a small estate and applied his scientific knowledge to improve the yield and quality of crops, an endeavour invaluable for Russia' s predominantly agricultural economy. Author not available, Mendeleyev, Dmitri Ivanovich (1834-1907). , The Hutchinson Dictionary of Scientific Biography, 01-01-1998. |