Russian chemist Dmitri Ivanovich Mendeleev was born in Tobolsk in the family of a headmaster.While training in the gymnasium Mendeleev had very mediocre grades,especially in the Latin language.In 1850 he entered the Department of natural Sciences faculty of physics and mathematics of the Main pedagogical Institute in St. Petersburg.
In 1856 Mendeleev defended at St. Petersburg University master's thesis,in 1857, was approved by the Privat-docent at the same University and taught a course in organic chemistry.In 1859-1861, Mendeleyev was in scientific business trip in Germany,where he worked in the laboratory of R. Bunsen and G. Kirchhoff in Heidelberg University. The periodic table(or periodic system of chemical elements) is a table which classifies the chemical elements by different properties,depending on the charge of the atomic nucleus.This system expresses in the form of a table,the periodic law of chemical elements,which in 1869 was opened by Russian scientist chemist D. I. Mendeleev.The first version of the table was developed by Mendeleev in the years 1869-1871,he determined the dependence of the properties of the chemical elements,atomic masses (then called atomic weights).
The opening of the Russian scientist,marked a new era in the history of science,this discovery made it possible not only to make a huge leap in chemistry,but also was invaluable to other areas of science.The periodic table gave a coherent system of information about the elements on the basis of it,the opportunity to make scientific conclusions,and even to anticipate some of the discoveries.