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Mendelayev, Dmitri Ivanovich

elements chemical table chemistry

[mende lay ef] (1834–1907) Russian chemist: devised periodic table of chemical elements.

Mendelayev grew up in Siberia, the last-born of a family of 14 children. His father, a teacher, became blind at this time, but his mother was a forceful woman and she reopened and ran a nearby glass factory to give an income. When Dmitri was 14 his father died and the factory was destroyed by fire; but the boy had done well at school and his mother decided that he deserved more education. They made the long trip to St Petersburg and he began to study chemistry, and was so successful (despite much illness) that he was given an award to study

The periodic table of the chemical elements. The horizontal rows (‘periods) and the vertical columns (‘groups’) both show progressive trends in chemical and physical properties of the elements, reflecting progressive change in the structure of the atoms. Hydrogen, with its uniquely simple atom, appears in both groups 1 and 7 with in Germany. Back in St Petersburg from 1861, he began his career as a teacher and researcher in the university.

His career was not smooth; he was irascible and outspoken, supported the students’ political ideas and quarrelled with two successive ministers of education. He and his wife divorced and he remarried, without waiting the 7 years then required by Russian law. Officially a bigamist, he was not directly penalized for this, but the priest was; Mendelayev, forced out of the university in 1890, became director of the Board for Weights and Measures in 1893. Mendelayev was more honoured outside Russia than within it, and he was never admitted to the Imperial Academy of Sciences, despite his work for the Russian chemical industry and his great scheme which brought order and prediction to inorganic chemistry; this was his periodic table (or periodic law or classification).

Mendelayev saw the need for a new textbook of chemistry in the 1860s, and in shaping his ideas for this book he prepared a series of cards, each listing the main properties of one chemical element; he liked playing patience as a relaxation. In arranging these, he was struck by the fact that if the 60 cards were placed in rows of suitably varying length, with most of the elements in order of increasing relative atomic mass, then elements with similar chemical features were found to lie in the vertical groups (the periodic law). Mendelayev did not know of primitive work on similar lines, and his went much further. In his table of 1868–9, he boldly transposed some pairs of elements on the basis that their claimed atomic masses must be in error if they were to fit the scheme; likewise he left spaces for three yet undiscovered elements. He predicted the properties of the latter from those of their known neighbours. By 1886 the predicted elements were discovered by other chemists, and their real properties were found to be in good accord with prediction. Later still, the noble gases and the transuranium elements were fitted into the table. The whole scheme brought order into chemistry by allowing a great range of known facts to be arranged and classified. It stands like work in physics or in biology as one of the great intellectual advances in science. It was devised on an entirely empirical basis and it was half a century later that work, and that of , provided an explanation for it in terms of atomic structure. Mendelayev produced his table when he was 34. It made him famous, and he worked on it for a few years, but then moved to a variety of other matters. It has framed and shaped ideas in inorganic chemistry ever since. In 1955 a new element, atomic number 101, was named mendelevium (Md) in his honour.

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