Dmitry Ivanovich Mendeleyev, Russian chemist, c 1905.

RUSSIA - SEPTEMBER 09: Photogravure after a photograph of Dmitry Ivanovich Mendeleyev (1834-1907). Born in Tobolsk, Russia, Mendeleyev trained as a teacher, and went on to study at Odessa, St Petersburg and Heidelberg universities, before becoming professor of chemistry at St Petersburg in 1866. He formulated the first periodic table of elements, grouping the elements according to their atomic structure and chemical properties. His work enabled chemists to identify 'families' of elements with similar chemical and physical properties and has influenced ideas in organic chemistry ever since. In 1955 a new element (no 101) was named mendelevium (Md) in his honour. From a collection of portraits of scientists published by Photographische Gesellschaft, Berlin, c 1910. (Photo by SSPL/Getty Images)