Dmitri Mendeleev/Definition

(1834-1907) [MEN-de-LAY-ev), Russian chemist, discovered that ordering the then (1869) known chemical elements, sixty-three in number, according to their increasing atomic weights, revealed a repeated cycle of recurrence of their chemical and physical properties, a discovery that permitted him to predict subsequently experimentally established revised values for the atomic weights of several elements and, spectacturally, the subsequently confirmed existence of yet undiscovered elements with atomic weights and properties required to fill in missing elements in an otherwise consistent periodicity in his ordering scheme, a scheme which chemists subsequently referred to as the periodic table of the chemical elements.