2019, the United Nations proclaimed the «International Year of the Periodic Table of the Chemical Elements». 150 years have passed since the discovery by the great Russian scientist D.I. Mendeleev of the Periodic Law and the Periodic System of Elements. The information on 63 elements available by that time (1869) was brought into a harmonious system and made it possible to predict the properties of a number of those elements that had not yet been discovered. D.I. Mendeleev himself spoke of his discovery as follows: «... The future does not threaten destruction with a periodic law, but only a superstructure and development are promised.» The superstructure turned out to be very significant – to date, the number of elements has reached 118, and the element that appeared in 1955 was called Mendeleev (Md, registered under number 101). Even during the life of the scientist, a number of predictions came true: gallium was discovered in 1875, scandium in 1879, and Germany in 1886. All of them were previously named because of their similarity with the known elements: ecaaluminium, ecabor and ecasilicium («eca» – from the Sanskrit word «one»), their properties were predicted and places were left in the periodic system of elements. The discovery of the predicted elements and the fact that the experimentally determined properties of the new elements coincided with the predicted ones led to the worldwide recognition of the Periodic Law. In 2007, at the International Materials Science Congress (TMS -2007), the Periodic System of Chemical Elements was named among the ten major achievements of mankind in the field of materials science and sciences, engaged in the development and study of the properties of new materials.