During the nineteenth century, many areas underwent a strong reformation, including chemistry. The periodic system of Mendeleev, formulated in 1869, led to a common understanding of the dependence of the position of simple substances in the periodic table, which established the relationship between the relative atomic mass, valency and property of the element.
Pre-Mendelean period of chemistry
Somewhat earlier, at the beginning of the nineteenth century, repeated attempts were made to systematize the chemical elements. The German chemist Döbereiner carried out the first serious systematization work in the field of chemistry. He determined that a number of similar substances in properties can be combined into groups - triads.
False ideas of a German scientist
The essence of the presented Döbereiner triad law was determined by the fact that the atomic mass of the desired substance is close to half the sum (average value) of the atomic masses of the last two elements of the triad table.
However, the absence of magnesium in a single subgroup of calcium, strontium and barium waserroneous.
This approach was a consequence of the artificial restriction of analogous substances to only tripartite unions. Döbereiner clearly saw the similarity in the chemical parameters of phosphorus and arsenic, bismuth and antimony. However, he limited himself to searching for triads. As a result, he could not come up with a correct classification of chemical elements.
Döbereiner certainly failed to divide the existing elements into triads, the law clearly indicated the presence of a relationship between the relative atomic mass and the properties of simple chemical substances.
The process of systematization of chemical elements
All subsequent attempts at systematization relied on the distribution of elements depending on their atomic mass. Subsequently, Döbereiner's hypothesis was used by other chemists. The formation of triads, tetrads and pentads appeared (combining into groups of three, four and five elements).
In the second half of the nineteenth century, several works appeared simultaneously, based on which Dmitry Ivanovich Mendeleev led chemistry to a complete systematization of chemical elements. A different structure of the periodic system of Mendeleev led to a revolutionary understanding and evidence of the distribution mechanism of simple substances.
Periodic system of elements of Mendeleev
At a meeting of the Russian chemical community in the spring of 1869, a notice was read by the Russian scientist D. I. Mendeleev about his discovery of the periodic law of chemical elements.
At the end of the same year, the first work was published"Fundamentals of Chemistry", it included the first periodic system of elements.
In November 1870, he showed his colleagues the addition "The natural system of elements and its use in indicating the qualities of undiscovered elements." In this work, D. I. Mendeleev first used the term "periodic law". The system of elements of Mendeleev, on the basis of the periodic law, determined the possibility of the existence of undiscovered simple substances and clearly indicated their properties.
Corrections and clarifications
As a result, by 1971, the periodic law and the periodic system of elements of Mendeleev were finalized and supplemented by a Russian chemist.
In the final article "Periodic Law of Chemical Elements", the scientist established the definition of the periodic law, which indicates that the characteristics of simple bodies, the properties of compounds, as well as the complex bodies formed by them, are determined by direct dependence according to their atomic weight.
Somewhat later, in 1872, the structure of Mendeleev's periodic system was reorganized into a classical form (short-period distribution method).
Unlike his predecessors, the Russian chemist fully compiled a table, introduced the concept of the regularity of the atomic weight of chemical elements.
Characteristics of the elements of the periodic system of Mendeleev and the patterns derived allowed the scientist to describe the properties of elements that have not yet been discovered. Mendeleev relied on the fact that the properties of each substance can be determined according to the characteristics of two neighboringelements. He called this the "star" rule. Its essence is that in the table of chemical elements to determine the properties of the selected element, it is necessary to orientate horizontally and vertically in the table of chemical elements.
Mendeleev's periodic system is able to predict…
The periodic table of elements, despite its accuracy and fidelity, was not fully recognized by the scientific community. Some of the world's great scientists openly ridiculed the ability to predict the properties of an undiscovered element. And only in 1885, after the discovery of the predicted elements - ekaaluminum, ekabor and ekasilicon (gallium, scandium and germanium), the new classification system of Mendeleev and the periodic law were recognized as the theoretical basis of chemistry.
At the beginning of the twentieth century, the structure of Mendeleev's periodic system was repeatedly corrected. In the process of obtaining new scientific data, D. I. Mendeleev and his colleague W. Ramsay came to the conclusion that it was necessary to introduce a zero group. It includes inert gases (helium, neon, argon, krypton, xenon and radon).
In 1911, F. Soddy proposed to place indistinguishable chemical elements - isotopes - in one cell of the table.
In the process of long and painstaking work, the table of the periodic table of chemical elements of Mendeleev was finally finalized and acquired a modern look. It consists of eight groups and seven periods. Groups are vertical columns, periods are horizontal. Groups are divided into subgroups.
The position of an element in the table indicates its valence, pure electrons and chemical features. As it turned out later, during the development of the table, D. I. Mendeleev discovered a random coincidence of the number of electrons of an element with its serial number.
This fact further simplified the understanding of the principle of the interaction of simple substances and the formation of complex ones. And also the process in reverse. The calculation of the amount of the obtained substance, as well as the amount necessary for the chemical reaction to proceed, has become theoretically available.
The role of Mendeleev's discovery in modern science
Mendeleev's system and his approach to the ordering of chemical elements predetermined the further development of chemistry. Thanks to a correct understanding of the relationship of chemical constants and analysis, Mendeleev was able to correctly arrange and group elements according to their properties.
The new table of elements makes it possible to clearly and accurately calculate data before the start of a chemical reaction, to predict new elements and their properties.
The discovery of the Russian scientist had a direct impact on the further course of development of science and technology. There is no technological field that does not involve the knowledge of chemistry. Perhaps, if such a discovery had not taken place, then our civilization would have taken a different path of development.
