On March 6, 1869, exactly 150 years ago, Russian chemist Dmitry Mendeleev (1834-1907) presented his periodic table of chemical elements - a graphic description of what was destined to go down in history as the Periodic Law, TASS reported.

The story of the discovery

At the middle of the 19th century, 63 chemical elements were known to science. Before Mendeleev’s discovery, attempts at arranging them in some logical way were made by Johann Doebereiner (1829), Alexander Chancourtois (1862), Julius Meyer (1864), John Newlands (1866) and others.

In 1867, Dmitry Mendeleev, a professor at the St. Petersburg University, started working on a fundamental text called The Principles of Chemistry. At a certain point, the scientist arrived at the conclusion that the properties and atomic masses of chemical elements were interrelated in a certain way. With this in mind, in 1869, Mendeleev put together a table that he called The Experiment of a System of Elements Based on Their Atomic Weight and Chemical Similarity and sent it to the printer’s on March 1 (O.S. February 17). Mendeleev also sent copies of the table bearing this date to his colleagues in Russia and abroad. Four days later, he formulated the periodic law in an article entitled The Dependence Between the Properties of the Atomic Weights of the Elements, published in the magazine of the Russian Chemical Society (currently D.I. Mendeleev Russian Chemical Society). In his publication, he described the law he discovered in the following way: "The elements, if arranged according to their atomic weight, exhibit an apparent periodicity of properties."

On March 18, 1869, the news of the periodic system of elements was announced at a meeting of the Russian Chemical Society. The man who broke the news was the society’s editor, Professor Nikolai Menshutkin. He was speaking on Mendeleev’s behalf at the scientist’s own request. Mendeleev was out of town at the moment.

Mendeleev spent a little more than two years improving his periodic system. He introduced periods and groups of elements, the position of each of them in the table, corrected the atomic mass of some of them (such as beryllium, indium, uranium, etc.), predicted the existence of a number of new elements and described their properties. In 1871, he finalized the Basics of Chemistry to come up with the final definition of the periodic law and a version of the system of elements pretty close to the current one. The scientist formulated the periodic law in the following way: "The properties of simple bodies, the constitution of their compounds, as well as the properties of the later are periodic functions of the atomic weights of the elements, because these properties are themselves the properties of the elements from which these bodies derive."

Mendeleev’s Periodic Law earned universal recognition as one of the pillars of theoretic chemistry after the discovery of elements he had predicted - gallium (Ga, 31st element) in France in 1875, scandium (Sc, 21st) in Sweden in 1879, and germanium (Ge, 32nd) in Germany in 1886.

The Royal Society of London awarded the Davy Medal to Dmitry Mendeleev for his accomplishment in 1882.

Periodic table

Mendeleev’s periodic law has undergone certain changes and been complemented by new elements, including artificially synthesized ones. All in all, more than 500 versions of it have been published. Two are the most widely spread ones: the short version (has eight groups, horizontal rows of elements) and the long version (18 rows). In 1989, the International Union of Pure and Applied Chemistry, IUPAC) recommended the long version. In the modern system, the elements are arranged in a two-dimensional table, in which each column (group) represents the basic physical and chemical properties, and the rows are periods of elements largely similar to each other.

As at the beginning of 2019, the Periodic Table listed 118 chemical elements (the last three were added in 2016). The names of some are related with Russia. Ruthenium (Ru) is one of the ways of spelling Russia in Latin. Dubnium (Db) was calledin honor of the research cluster Dubna; Moscovium (Mc), in honor of the Moscow Region where the United Institute for Nuclear Research is located; Mendelevium (Md), in honor of Dmitry Mendeleev; Oganesson (Og), in honor of physicist Yuri Oganesian; Samarium (Sm), in honor of Russian mining engineer Vasily Samarsky-Bykhovets; and Flerovium (Fl) in honor of Soviet nuclear physicist Georgy Flerov.

The Periodic Table played an important role in studying the properties of chemical elements and expanding the knowledge of the structure of matter. It serves as the scientific basis for teaching general and inorganic chemistry and also nuclear physics.

Its first version, published on March 1, 1869, is kept at the D.I. Mendeleev Museum Archive at St. Petersburg University. The first version of the table made for demonstration in public (graphic image) at the request of Dmitry Mendeleev himself in 1876 can be seen in the Large Chemistry Lecture Hall of the Visileostrovsky Campus of the St. Petersburg University. A copy of the Periodic Table dated 1885 was discovered at the University of St. Andrews in Scotland in 2014.