Mendeleev completes and presents the periodic table

Background. Mendeleev, a founder of the Russian Chemical Society, began arranging elements by atomic weights in February 1869. His work aimed to classify chemical elements into periods and groups, demonstrating that properties depend on atomic mass. This arrangement allowed him to correct known element properties and predict characteristics of missing elements, creating the first generally accepted periodic table.

Formulation of the Periodic Law. Mendeleev formulated the periodic law as a dependence of chemical properties on atomic mass. He arranged 63 elements in columns, noting recurring properties. His 1869 list initially misplaced seven elements, including rare-earth metals, which he later revised in 1870 by adjusting atomic weights and valences to improve the table's accuracy.

Presentation to the Russian Chemical Society. Mendeleev made a formal presentation to the Russian Chemical Society in Saint Petersburg, titled 'The Dependence between the Properties of the Atomic Weights of the Elements.' This presentation described elements by atomic weight and valence. His printed table appeared in the Society's journal in May 1869, solidifying his formulation of the periodic law.