periodic table elements periodic table definition chemistry

The basic concepts of chemistry, such as atom and molecule, and the determination of atomic weights, were eventually clarified only in 1860 when, at the initiative of August Kekulé (1829–1896) the first International Congress of Chemistry took place in Karlsruhe. Title page of “The Sceptical Chymist” by R. In 1829, Johann Wolfgang Döbereiner (1780–1849) united the elements into groups of three elements, the so-called triads, pointing out that some properties of the elements and their compounds are arithmetic means of the properties of the two end elements.

He also introduced modern chemical symbols. In 1815, Jöns Jacob Berzelius (1779–1848) made a classification of elements, compounds and minerals and divided elements on the basis of their chemical and physical properties as metals and nonmetals (metalloids). –1794) made the first list of chemical elements in 1789, which contained 33 elements, including light and heat. The first scientific definition of a chemical element as a pure chemical substance which cannot be subdivided into simpler ones, was given by Robert Boyle (1627–1691) in 1661 ( Fig. In this ancient age, when people believed in the existence of many gods, Democritus assumed that only matter exists. The creator of atomism Democritus postulated: “There is only matter and void”. The pursuit of human thought to seek unity in the infinite multitude gave birth to the idea of primary matter. The creation of the Periodic Table of the Chemical Elements is one of the greatest generalizations in physicochemical science after the atomic molecular theory and the laws of thermodynamics, a synthesis that links the lessons learned from the experience gained over time into a unified system and thus creates one of the foundations for further development of natural sciences. Mendeleev by Vaska Popova-Balarewa (1956).

Periodic table elements periodic table definition chemistry