Dmitri Mendeleev
Unaware of the earlier work on periodic tables going on in the 1860s, he made the following table:
By adding additional elements following this pattern, Mendeleev developed his extended version of the periodic table. On 6 March 1869, he made a formal presentation to the Russian Chemical Society, titled "The Dependence between the Properties of the Atomic Weights of the Elements", which described elements according to both atomic weight (now called "relative atomic mass") and valence. This presentation stated that
Periodic trends
Discovery of Periodic Law constitutes one of the most singularly important events in the history of chemical science. Almost every chemist makes extensive and continued use of Periodic Law. Periodic Law also led to the development of the periodic table, which is widely used nowadays.