In 1869 Russian chemist Dimitri Mendeleev started the development of the periodic table, arranging chemical elements by atomic mass. He predicted the discovery of other elements, and left spaces open in his periodic table for them. In 1886 French physicist Antoine Bequerel first discovered radioactivity.Dmitri Ivanovich Mendeleev (often romanized as Mendeleyev or Mendeleef) (English: /ˌmɛndəlˈeɪəf/ MEN-dəl-AY-əf;[2] Russian: Дмитрий Иванович Менделеев,[note 1] tr. Dmítriy Ivánovich Mendeléyev, IPA: [ˈdmʲitrʲɪj ɪˈvanəvʲɪtɕ mʲɪnʲdʲɪˈlʲejɪf] (listen); 8 February 1834 – 2 February 1907 [OS 27 January 1834 – 20 January 1907]) was a Russian chemist and inventor. He formulated the Periodic Law, created a farsighted version of the periodic table of elements, and used it to correct the properties of some already discovered elements and also to predict the properties of eight elements yet to be discovered.http://vserod.com/http://vserod.com/tables/2d/http://vserod.com/tables/3d/Rybnikov Yuri Stepanovich (March 15, 1955) - researcher, creator of the “Periodic Table of Electroatoms” of RUSs, the “Unified Field Theory” , a methodology for constructing electrostructures of electroatoms that combined physics, chemistry, electricity, and RUSs (mathematics) into a single Knowledge System.Invented, developed and introduced in the USSR powder polymer coating technology.He taught at the Moscow State Technical University of Radio Engineering Electronics and Automatics (MSTU MIREA), associate professor.