Periodic Mendeleev's system and periodic law

During the nineteenth century, many directions, including chemistry, underwent a strong reformation. The periodic system of Mendeleev, formulated in 1869, led to a unified understanding of the dependence of the position of simple substances in the periodic table, which established the relationship between the relative atomic mass, valence, and the property of the element.

Domedeleevsky period of chemistry

Somewhat earlier, at the beginning of the nineteenth century, repeated attempts were made to systematize the chemical elements. German chemist Döbereiner conducted the first serious work on systematization in the field of chemistry. He determined that a number of similar substances by properties can be combined into groups - triads.

The erroneousness of the views of the German scientist

The essence of the presented law of the Döbereiner triads was determined by the fact that the atomic mass of the sought substance is close to the half-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 was erroneous.

This approach was a consequence of the artificial restriction of similar substances only tripartite unions. Döbereiner saw well the similarity in the chemical parameters of phosphorus and arsenic, bismuth and antimony. However, he limited himself to finding triads. As a result, he could not come to the correct classification of chemical elements.

To divide the existing elements into triads, Döbereiner certainly did not succeed, the law clearly indicated the presence of the relationship between the relative atomic mass and the properties of the chemical simple substances.

The process of systematization of chemical elements

All subsequent attempts to systematize relied on the distribution of elements depending on their atomic mass. Later, the Döbereiner hypothesis was used by other chemists. There appeared the formation of triads, tetrads and pentads (grouping into three, four and five elements).

In the second half of the nineteenth century several works appeared simultaneously, based on which Dmitry Ivanovich Mendeleyev brought chemistry to the full systematization of chemical elements. Another structure of Mendeleyev's periodic system led to a revolutionary understanding and the obvious mechanism of distribution of simple substances.

Periodic system of Mendeleev elements

At a meeting of the Russian chemical community in the spring of 1869, a notice was sent to the Russian scientist DI Mendeleyev about the discovery of a periodic law of chemical elements by him. At the end of the same year, the first work "Fundamentals of Chemistry" was published, the first periodic system of elements was included.

In November 1870, he showed colleagues the addition of the "Natural System of Elements and its use to indicate the qualities of undiscovered elements." In this work DI Mendeleyev first used the term "periodic law". The system of Mendeleev elements on the basis of the periodic law determined the possibility of the existence of non-open simple substances and clearly indicated their properties.

Corrections and clarifications

As a result, by 1971, the periodic law and the periodic system of Mendeleev's elements were refined and supplemented by a Russian chemist.

In the final article "Periodic validity of chemical elements," the scientist established the definition of a periodic law, which states that the characteristics of simple bodies, the properties of compounds, and the complex bodies formed by them are determined by direct dependence according to their atomic weight.

Somewhat later, in 1872, the structure of the periodic system of Mendeleyev was reorganized into a classical form (short-period mode of distribution).

Unlike its predecessors, the Russian chemist made a table in full, introduced the concept of the regularity of the atomic weight of chemical elements.

The characteristics of the elements of Mendeleev's periodic system and the derived regularities 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 neighboring elements. He called it the rule of the "star." Its essence lies in the fact that in the table of chemical elements for determining the properties of the selected element, it is necessary to orient horizontally and vertically in the table of chemical elements.

The periodic system of Mendeleev is able to predict ...

The table of Mendeleev's elements, despite its accuracy and fidelity, was not fully recognized by the scientific community. Some great world-renowned scholars openly ridiculed the possibility of predicting the properties of an undiscovered element. And only in 1885, after the discovery of the predicted elements - ekaaluminum, ekabor and ekasilicia (gallium, scandium and germanium), Mendeleev's new classification system and periodic law were recognized as the theoretical basis of chemistry.

In the early twentieth century, the structure of the periodic system of Mendeleyev was repeatedly corrected. In the process of obtaining new scientific data, DI Mendeleev and his colleague U. Ramsay came to the conclusion that it was necessary to introduce a zero group. It included inert gases (helium, neon, argon, krypton, xenon and radon).

In the year nineteen eleventh, F. Soddy made a proposal to place indistinguishable chemical elements - isotopes - in one cell of the table.

In the process of long and painstaking work, the periodic table of Mendeleyev's chemical elements was finalized and acquired a modern look. It included eight groups and seven periods. Groups are vertical columns, periods are horizontal. In groups, division into subgroups is defined.

The position of the element in the table indicates its valence, purely electrons and chemical characteristics. As it turned out later, during the development of the table, DI Mendeleev found 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 substances. And also the process in the opposite direction. Calculation of the amount of the substance obtained, as well as the necessary for the chemical reaction to proceed, became theoretically available.

The role of Mendeleev's discovery in modern science

The Mendeleev system and its approach to the ordering of chemical elements predetermined the further development of chemistry. Thanks to a correct understanding of the relationship between chemical constants and analysis, Mendeleev was able to correctly group and group the elements according to their properties. A new table of elements makes it possible to clearly and accurately calculate the data before the start of the chemical reaction, to predict new elements and their properties.

The discovery of the Russian scientist had a direct impact on the further development of science and technology. There is no technological area that does not involve the knowledge of chemistry. Perhaps, if such a discovery had not taken place, our civilization would have followed a different path of development.