During the period of the nineteenth century, many directions 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 element property.
Domendeleev period of chemistry
Somewhat earlier, at the beginning of the nineteenth century, repeated attempts were made to systematize chemical elements. The German chemist Döbereiner carried out 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 fallacy 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 desired substance is close to the half-sum (average value) of the atomic masses of the last two elements of the triad table.
However, the lack of magnesium in a single subgroup of calcium, strontium and barium was erroneous.
This approach was a consequence of the artificial limitation of similar substances only by triple alliances. Debeereiner clearly saw the similarities 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.
Of course, Döbereiner did not succeed in dividing 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 organizing chemical elements
All subsequent attempts to systematize relied on the distribution of elements depending on their atomic mass. Subsequently, the Döbereiner hypothesis was used by other chemists. The formation of triads, notebooks and pentads (joining in groups of three, four and five elements) appeared.
In the second half of the nineteenth century, several works appeared simultaneously, based on which Dmitry Ivanovich Mendeleev led chemistry to the full systematization of chemical elements. A different structure of the periodic system of Mendeleev led to a revolutionary understanding and evidence of the mechanism of distribution of simple substances.
Periodic table of the elements of Mendeleev
At a meeting of the Russian chemical community in the spring of 1869, a notice was read out by a 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, Fundamentals of Chemistry, was published, and the first periodic system of elements was included in it.
In November 1870, he showed his colleagues the supplement "The natural system of elements and its use to indicate 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 a periodic law determined the possibility of the existence of not discovered 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 finalized and supplemented by a Russian chemist.
In the final article, “Periodic legitimacy of chemical elements,” the scientist established a 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 a direct relationship according to their atomic weight.
A little later, in 1872, the structure of the periodic system of Mendeleev was reorganized into a classical form (short-period distribution method).
Unlike its predecessors, the Russian chemist compiled the table fully, introduced the concept of the pattern of atomic weight of chemical elements.
The characterization of the elements of the periodic system of Mendeleev and the derived patterns 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 "star" rule. Its essence is that in the table of chemical elements to determine the properties of the selected element it is necessary to navigate 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 great world-famous scientists openly ridiculed the ability to predict the properties of an undiscovered element. And only in 1885, after the discovery of the predicted elements - ecaaluminium, ecaborium and ecasilicium (gallium, scandium and germanium), the new Mendeleev classification system and the periodic law were recognized as the theoretical basis of chemistry.
At the beginning of the twentieth century, the structure of the periodic system of Mendeleev was repeatedly corrected. In the process of obtaining new scientific data, D.I. Mendeleev and his colleague W. Ramzai 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 nineteen eleven, F. Soddy proposed placing indistinguishable chemical elements - isotopes - in one cell of the table.
In the process of long and painstaking work, the periodic table of the periodic system of chemical elements of Mendeleev 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 valency, purely electrons, and chemical characteristics. As it turned out later, during the development of the table, D. I. Mendeleev discovered a random coincidence of the number of electrons of the element with its serial number.
This fact further simplified the understanding of the principle of interaction of simple substances and the formation of complex ones. And also the process in the opposite direction. The calculation of the amount of the obtained substance, as well as the necessary for the course of the chemical reaction became 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 the correct understanding of the relationship between chemical constants and analysis, Mendeleev was able to correctly compose and group elements according to their properties.
The new table of elements makes it possible to clearly and clearly 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 course of development of science and technology. There is no technological field that does not involve knowledge of chemistry. Perhaps if such a discovery did not take place, then our civilization would take a different path of development.