The periodic table of chemical elements-history, nature, meaning

Abstract

By decision of the UN General Assembly 2019 was declared an International Year of the Periodic Table of Chemical Elements. On this occasion, in Bulgaria, an anniversary postage stamp was issued. Search for a link between the properties of the chemical elements and their atomic weight was undertaken before Mendeleev by many chemists. It is characteristic of all these classifications that the observed proximity in the properties of the elements has been attributed to chance. Mendeleev, however, was the only one who perceived that beyond the periodicity of the elements properties there is an important natural law. With the discovery of the structure of atoms, the periodic table of chemical elements found its scientific explanation. The periodic table set an important task to chemistry to look for the relationship between the composition and the properties of the substances, including the disclosure of the regularities which are the basis of the so-called "anomalies".