Periodic Mendeleev's system and periodic law
During the nineteenth century, a strong reformationhave undergone many directions, including chemistry. 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.
The Domodedeleev period of chemistry
Somewhat earlier, in the early 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.
Misconceptions 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 the result of artificialrestrictions 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 the search for triads. As a result, he could not come to the correct classification of chemical elements.
Split existing elements into triadsDoubbereir certainly did not succeed, the law clearly indicated the presence of the relationship between the relative atomic mass and the properties of chemical simple substances.
The process of systematization of chemical elements
All subsequent attempts to systematize relied onon 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 appearedat the same time several works, based on which Dmitry Ivanovich Mendeleev brought chemistry to the full systematization of chemical elements. The different 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 notification was sent to the Russian scientist DI Mendeleyev about the discovery of a periodic law of chemical elements.At the end of the same year, the first work, The Foundations of Chemistry, was published, the first periodic system of elements was included.
In November 1870, he showed his colleagues an addition"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 legalitychemical elements, "the scientist established the definition of the 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 Mendeleyev's periodic system was reorganized into a classical form (short-period mode of distribution).
Unlike its predecessors, the Russian chemist made a table fully, introduced the concept of the regularity of the atomic weight of chemical elements.
Characteristics of the elements of the periodic tableMendeleev and derived regularities allowed the scientist to describe the properties of elements that are not yet open. 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 ...
Table of Mendeleev elements, despite itsaccuracy and fidelity, was not recognized by the scientific community as fully. 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-ekaaluminium, ekabor and ekasilicia (gallium, scandium and germanium), Mendeleev's new classification system and periodic law were recognized as the theoretical basis of chemistry.
At the beginning of the twentieth century, the structure of the periodicMendeleyev's system 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 1,110, F. Soddy proposed to place indistinguishable chemical elements - isotopes - in one cell of the table.
In the process of long and painstaking work, the tableperiodic system of chemical elements Mendeleyev 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 itsvalence, pure electrons and chemical features. As it turned out later, during the development of the table, DI Mendeleev discovered a random coincidence of the number of electrons of an element with its serial number.This fact further facilitated understandingthe 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, became theoretically available.
The role of Mendeleev's discovery in modern science
The Mendeleyev system and its approach to orderingchemical 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 impacton 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.