Dmitri Mendeleev

Dimitri Ivanovich Mendeleev (1834-1907), Russian chemist, discovered a way to order the then known (1869) chemical elements, sixty-three in number, according to their increasing atomic weights, in such a way as to reveal a repeated cycle of recurrence, every seven elements, of their chemical and physical properties &mdash; the properties recurred as functions of the elements' atomic weights &mdash; and to permit the prediction of subsequently experimentally established improved values for the atomic weights of certain elements and, importantly, of the existence of yet undiscovered elements with atomic weights and properties requisite to fill in the gaps in his ordering scheme, a scheme which chemists subsequently referred to as the periodic table of the chemical elements.

When, within a few years of the announcement of his ordering scheme, chemists discovered three new chemical elements (gallium, scandium, germanium) that accorded with his prediction of their atomic weights and properties, and with confirmation of his revised atomic weights for specified elements, Mendeleev's contemporaries worldwide recognize his discovery as a natural law of chemistry transcending taxonomy, and as a fundamental contribution to the understanding of the nature of physical reality, leading his successors, notably the 20th century Danish physicist, Niels Bohr, to formulate a theory of atomic structure and its regularities that explained Mendeleev's periodic law and the deviations to it discovered with the ever expanding discovery of new elements.

As the theory of evolution ineluctably evokes the name of Charles Darwin, and the theory of relativity the name of Albert Einstein, the periodic law of the chemical elements the name of Dimitri Mendeleev.