Mendeleev, Dmitri Ivanovich, mehn duh LAY uhf, DMEE trih ih VAH nuh vihch (1834-1907), was a Russian chemist who developed a form of the periodic law, a basic principle in chemistry. His law states the properties of chemical elements recur in regular patterns when the elements are arranged according to their mass (amount of matter). Mendeleev's work, together with that of the German chemist Julius Lothar Meyer, led to the periodic table, a systematic arrangement of the elements (see Element, Chemical [Periodic table of the elements]).