Dmitri Mendeleyév, the father of the periodic table of the chemical elements

Tobolsk, Russia, 1834-St. Petersburg, 1907

Mendeléiev is the most universal Russian chemist. The most popularly known work of his is the periodic table of chemical elements..

It all started when Mendeléiev traveled in September 1860 to Karlsruhe, Germany, to attend the First International Chemical Congress. This congress was attended by 140 of the most eminent chemists in the world at that time. The speeches Mendeléiev heard there aroused such interest that it lasted the rest of his life.

In 1860 chemistry was still confused and there was no general consensus on the most basic aspects of this science. The confusion was such that there were 20 different formulas to describe fairly simple compounds. Certain elements had long been known to share similar properties, and chemists had begun to wonder if they could be classified as Linnaeus had classified animals.

In 1864, the English chemist John Newlands discovered that if the elements were arranged in the order of their atomic weights, the resulting table showed a periodicity, which meant that similar features recurred at regular intervals. Mendeléiev was aware of the work of Newlands, but he did not entirely agree with the developments that he had made, and therefore he tried to understand the relationship between one element and another, but resolving the defects that he perceived in the Newlands scheme. . Thus, he grouped the elements according to their shared properties, which led him to see that the elements could be arranged in horizontal rows in ascending order of atomic weight, and in vertical columns according to their chemical characteristics... leaving gaps where the patterns seemed require them.

This idea was published in a paper entitled Relation between the properties of the elements and their atomic weight, which contained his periodic law which stated that if the known elements were listed in order of ascending atomic weight they would show a repeating pattern of ascending valences and descending (the proportion in which they are combined with other elements) and in addition, they would form groups that show a recurring pattern of other characteristics. With his discovery, Mendeléiev was able to rearrange 17 elements in the table based on their chemical properties, implying that their accepted atomic weights were incorrect. He was also able, thanks to the gaps in his table, to postulate the existence of three hitherto unknown elements and even predict their properties.

The reaction of the scientific community to Mendeleev's writing was initially very cautious, but when it was discovered that the accepted atomic weights of some elements were actually incorrect, his ideas began to be taken seriously. And fifteen years later, the three gaps in his table were filled by the discovery of gallium (1875), scandium (1879), and germanium (1886), all of which possessed the characteristics he had predicted. Although he was not the first to suggest that it was possible to place the elements in an order that would show his periodicity, Mendeléiev, unlike his predecessors, showed that there was an underlying logic that dictated his table.

His fame spread and he was recognized throughout the world, except in his country, where he was denied admission to the Imperial Russian Academy of Sciences in Saint Petersburg on four occasions. Nor did he have any luck with the Nobel Prize for Chemistry, which he lost by a vote in 1906 in favor of the French chemist Ferdinand Frédéric Henry Moissan (1852-1907), "for the isolation of fluorine and for putting the electric furnace into service for science that got his name."

Since it was created, Mendeléiev's table has been modified, but it is still recognizable because it discovered the fundamental relationship between the elements, although he had not the slightest idea of how their atoms were joined. Today the periodic table contains 109 elements, compared to the 63 he knew of. The elements of the periodic table and the compounds they form explain, with their physical and chemical characteristics, the behavior of the material world that surrounds us. The human being is chemistry: in our body there are 60 different chemical elements, although not all of them are in the same proportion.