He is a Russian chemist, who developed the periodic classification of the elements. In his final version of the periodic table he left gaps, foretelling that they would be filled by the elements which were not known at that time and predicting the properties of three of those elements.
Since 1864 he could not find a textbook that met his needs, he set about writing his own. As a result there appeared the book “The Principles of chemistry”, a classical textbook. While writing the book he began to investigate the relationships between chemical elements. After the English chemist and physicist John Dalton he had developed the idea of atomic weight, different chemists were looking for arithmetic connections between the elements. Out of this research there came the periodic table. Johann Dobereiner and William Odling were the most prominent among the chemists who attempted to arrange the elements into a logical order. It was Mendeleev, however, who formulated the periodic law, according to which all known elements are arranged in order of increasing their atomic weight. It became very useful in radioactive decay process by which one element is transformed into another.
He was also a practical man, aware of the necessity to use science in solving the problems of the world. We know that not all countries apply the Periodic Table of elements proposed by D.I. Mendeleev, but we are the students who study chemistry in schools and Universities of Russia and use this Table very often. And we are thankful to D.I. Mendeleev for this discoveries.