DMITRI IVANOVICH MENDELEYEV
Mendeleyev, the great Russian scientist, was born in Tobolsk in1834. At the age of 16 he entered the Pedagogical Institute in St. Petersburg . He graduated from the Institute in 1855. In 1867 he became professor of Chemistry at the Chair of General Chemistry at the St. Petersburg University , the leading University of the country. During the summer Mendeleyev worked hard at his lectures. He read all his notes. He made those notes during years of study and investigation. But the more Mendeleyev worked the harder his task seemed to him.
In autumn he began his course of lectures came to listen to him. Besides this course of lectures Mendeleyev began to work on a new book. He called it “Principles of Chemistry ”. By that time с hemists knew 63 different elements. Chemists knew many of their properties but there was not general system. Mendeleyev searched for a general law. He thought there must be some fundamental property characteristic of an element. After many experiments he found that that property is the atomic weight. That's how in the spring of 1869 he discovered the Periodic System. All the chemical elements fell into a natural order. There were some blanks in the Table at that time, but Mendeleyev described the properties of some of the undiscovered elements. Mendeleyev not only discovered the Periodic Law but used it for further development of science. Up to the present time scientists use Mendeleyev's Periodic Table in their scientific work.