Dmitri Ivanovich Mendeléev

February 7, 1834 - February 2, 1907

Russian chemist

Mendeleev was born in Tobolsk, Siberia, but was educated in St. Petersburg where he lived virtually all his life. He taught at St. Petersburg University and there wrote books and published his concept of chemical periodicity. In 1869, as Mendeleev was writing a chapter of his textbook on chemistry, he was shuffling pieces of paper on which he had written the names and properties of the known elements. He realized that, if the elements were arranged in order of increasing atomic mass, there were properties that repeated several times. That is, he saw that there was a periodicity to the properties of the elements, and he summarized this in a table.

The most important feature of Mendeleev's table was that he left empty spaces; he realized that these spaces would be filled by as-yet undiscovered elements. Mendeleev aided the discovery of the new elements by predicting their properties with remarkable accuracy, and he even suggested the geographical regions in which minerals containing the elements could be found. Mendeleev predicted the properties of the elements gallium, scandium, and germanium, and these elements were discovered in 1875, 1879 and 1886, respectively.

It is interesting that Mendeleev did little else with chemical periodicity after his initial articles. He went on to other interests, among them studying the natural resources of Russia and their commercial applications. In 1876 he visited the United States to study the fledgling oil industry and was much impressed with the industry but not with the country. He found Americans uninterested in science, and he felt the country carried on the worst features of European civilization.

All pictures of Mendeleev show him with long hair. He made it a rule to cut his hair only once a year, in the spring, whether he had to appear at an important occasion or not.