DISCOVERY OF THE PERIODIC LAW
The periodic law was discovered by D. I. Mendeleev while working on the text of the textbook "Fundamentals of Chemistry", when he encountered difficulties in systematizing the factual material. By mid-February 1869, thinking over the structure of the textbook, the scientist gradually came to the conclusion that the properties of simple substances and the atomic masses of elements are connected by a certain pattern.
The discovery of the periodic table of elements was not made by chance, it was the result of enormous work, long and painstaking work, which was spent both by Dmitry Ivanovich himself and by many chemists from among his predecessors and contemporaries. “When I began to finalize my classification of the elements, I wrote on separate cards each element and its compounds, and then, arranging them in the order of groups and rows, I received the first visual table of the periodic law. But this was only the final chord, the result of all previous work ... "- said the scientist. Mendeleev emphasized that his discovery was the result that completed twenty years of thinking about the relationships between elements, thinking from all sides of the relationship of elements.
On February 17 (March 1), the manuscript of the article, containing a table entitled "An experiment on a system of elements based on their atomic weight and chemical similarity," was completed and submitted for printing with notes for compositors and with the date "February 17, 1869." The report on the discovery of Mendeleev was made by the editor of the Russian Chemical Society, Professor N. A. Menshutkin, at a meeting of the society on February 22 (March 6), 1869. Mendeleev himself was not present at the meeting, since at that time, on the instructions of the Free Economic Society, he examined the cheese factories of Tverskaya and Novgorod provinces.
In the first version of the system, the elements were arranged by scientists in nineteen horizontal rows and six vertical columns. On February 17 (March 1), the discovery of the periodic law was by no means completed, but only began. Dmitry Ivanovich continued its development and deepening for almost three more years. In 1870, Mendeleev published the second version of the system (The Natural System of Elements) in Fundamentals of Chemistry: horizontal columns of analogous elements turned into eight vertically arranged groups; the six vertical columns of the first version turned into periods beginning with an alkali metal and ending with a halogen. Each period was divided into two rows; elements of different rows included in the group formed subgroups.
The essence of Mendeleev's discovery was that with an increase in the atomic mass of chemical elements, their properties do not change monotonously, but periodically. After a certain number of elements of different properties, arranged in ascending atomic weight, the properties begin to repeat. The difference between Mendeleev's work and the works of his predecessors was that Mendeleev had not one, but two bases for classifying elements - atomic mass and chemical similarity. In order for the periodicity to be fully respected, Mendeleev corrected the atomic masses of some elements, placed several elements in his system contrary to the then accepted ideas about their similarity with others, left empty cells in the table where elements that were not yet discovered should have been placed.
In 1871, on the basis of these works, Mendeleev formulated the Periodic Law, the form of which was somewhat improved over time.
The Periodic Table of the Elements had a great influence on the subsequent development of chemistry. It was not only the first natural classification of the chemical elements, which showed that they form a coherent system and are in close connection with each other, but was also a powerful tool for further research. At the time when Mendeleev compiled his table on the basis of the periodic law he had discovered, many elements were still unknown. Mendeleev was not only convinced that there must be elements yet unknown to fill these places, but he also predicted the properties of such elements in advance, based on their position among other elements of the periodic system. Over the next 15 years, Mendeleev's predictions were brilliantly confirmed; all three expected elements were discovered (Ga, Sc, Ge), which was the greatest triumph of the periodic law.
DI. Mendeleev handed over the manuscript "Experience of a system of elements based on their atomic weight and chemical similarity" // Presidential Library // A day in history http://www.prlib.ru/History/Pages/Item.aspx?itemid=1006
RUSSIAN CHEMICAL SOCIETY
The Russian Chemical Society is a scientific organization founded at St. Petersburg University in 1868 and was a voluntary association of Russian chemists.
The need to create the Society was announced at the 1st Congress of Russian Naturalists and Doctors, held in St. Petersburg in late December 1867 - early January 1868. At the Congress, the decision of the participants in the Chemical Section was announced:
The Chemistry Section declared a unanimous desire to unite in the Chemical Society for the communication of the already established forces of Russian chemists. The section believes that this society will have members in all cities of Russia, and that its publication will include the works of all Russian chemists, printed in Russian.
By this time, chemical societies had already been established in several European countries: the London Chemical Society (1841), the Chemical Society of France (1857), the German Chemical Society (1867); The American Chemical Society was founded in 1876.
The charter of the Russian Chemical Society, drawn up mainly by D. I. Mendeleev, was approved by the Ministry of Education on October 26, 1868, and the first meeting of the Society was held on November 6, 1868. Initially, it included 35 chemists from St. Petersburg, Kazan, Moscow, Warsaw , Kiev, Kharkov and Odessa. The first President of the RCS was N. N. Zinin, the secretary was N. A. Menshutkin. Members of the society paid membership fees (10 rubles per year), the admission of new members was carried out only on the recommendation of three existing ones. In the first year of its existence, the RCS grew from 35 to 60 members and continued to grow smoothly in subsequent years (129 in 1879, 237 in 1889, 293 in 1899, 364 in 1909, 565 in in 1917).
In 1869, the Russian Chemical Society got its own printed organ - the Journal of the Russian Chemical Society (ZhRHO); the magazine was published 9 times a year (monthly, except for the summer months). From 1869 to 1900, the editor of the ZhRHO was N. A. Menshutkin, and from 1901 to 1930 - A. E. Favorsky.
In 1878, the RCS merged with the Russian Physical Society (founded in 1872) to form the Russian Physical and Chemical Society. The first Presidents of RFHO were A. M. Butlerov (in 1878–1882) and D. I. Mendeleev (in 1883–1887). In connection with the merger, in 1879 (from the 11th volume) the Journal of the Russian Chemical Society was renamed into the Journal of the Russian Physical and Chemical Society. The periodicity of the publication was 10 issues per year; The journal consisted of two parts - chemical (LRHO) and physical (LRFO).
For the first time, many works of the classics of Russian chemistry were published on the pages of the ZhRHO. We can especially note the works of D. I. Mendeleev on the creation and development of the periodic system of elements and A. M. Butlerov, connected with the development of his theory of the structure of organic compounds; research by N. A. Menshutkin, D. P. Konovalov, N. S. Kurnakov, and L. A. Chugaev in the field of inorganic and physical chemistry; V. V. Markovnikov, E. E. Vagner, A. M. Zaitsev, S. N. Reformatsky, A. E. Favorsky, N. D. Zelinsky, S. V. Lebedev and A. E. Arbuzov in the field of organic chemistry. During the period from 1869 to 1930, 5067 original chemical studies were published in the ZhRHO, abstracts and review articles on certain problems of chemistry, and translations of the most interesting works from foreign journals were also published.
RFHO became the founder of the Mendeleev Congresses on General and Applied Chemistry; the first three congresses were held in St. Petersburg in 1907, 1911 and 1922. In 1919, the publication of the ZhRFKhO was suspended and resumed only in 1924.
Alchemists also tried to find a law of nature, on the basis of which it would be possible to systematize the chemical elements. But they lacked reliable and detailed information about the elements. By the middle of the XIX century. knowledge about chemical elements became sufficient, and the number of elements increased so much that a natural need arose in science to classify them. The first attempts to classify elements into metals and non-metals proved to be untenable. The predecessors of D.I. Mendeleev (I.V. Debereiner, J.A. Newlands, L.Yu. Meyer) did a lot to prepare the discovery of the periodic law, but could not comprehend the truth. Dmitry Ivanovich established a connection between the mass of elements and their properties.
Dmitry Ivanovich was born in Tobolsk. He was the seventeenth child in the family. After graduating from a gymnasium in his native city, Dmitry Ivanovich entered the Main Pedagogical Institute in St. Petersburg, after graduating from which he went on a scientific trip abroad with a gold medal for two years. After returning, he was invited to St. Petersburg University. Starting to read lectures on chemistry, Mendeleev did not find anything that could be recommended to students as a teaching aid. And he decided to write a new book - "Fundamentals of Chemistry".
The discovery of the periodic law was preceded by 15 years of hard work. On March 1, 1869, Dmitry Ivanovich planned to leave St. Petersburg for the province on business.
The periodic law was discovered on the basis of the characteristics of the atom - the relative atomic mass .
Mendeleev arranged the chemical elements in ascending order of their atomic masses and noticed that the properties of the elements are repeated after a certain interval - a period, Dmitry Ivanovich placed the periods one under the other., so that similar elements were located one under the other - on the same vertical, so the periodic system was built elements.
March 1, 1869 The formulation of the periodic law by D.I. Mendeleev.
The properties of simple substances, as well as the forms and properties of compounds of elements, are in a periodic dependence on the magnitude of the atomic weights of the elements.
Unfortunately, at first there were very few supporters of the periodic law, even among Russian scientists. There are many opponents, especially in Germany and England.
The discovery of the periodic law is a brilliant example of scientific foresight: in 1870, Dmitry Ivanovich predicted the existence of three then unknown elements, which he called ekasilicium, ekaaluminum and ecabor. He was also able to correctly predict the most important properties of the new elements. And after 5 years, in 1875, the French scientist P.E. Lecoq de Boisbaudran, who knew nothing about the work of Dmitry Ivanovich, discovered a new metal, calling it gallium. In a number of properties and the method of discovery, gallium coincided with ekaaluminum predicted by Mendeleev. But his weight was less than predicted. Despite this, Dmitry Ivanovich sent a letter to France, insisting on his prediction.
The scientific world was stunned that Mendeleev's prediction of properties ekaaluminum
turned out to be so accurate. From this moment, the periodic law begins to assert itself in chemistry.
In 1879, L. Nilson discovered scandium in Sweden, which embodied the predicted by Dmitry Ivanovich ekabor
.
In 1886, K. Winkler discovered germanium in Germany, which turned out to be exasilicon
.
But the genius of Dmitry Ivanovich Mendeleev and his discoveries are not only these predictions!
In four places of the periodic system, D. I. Mendeleev arranged the elements out of order of increasing atomic masses:
As early as the end of the 19th century, D.I. Mendeleev wrote that, apparently, the atom consists of other smaller particles. After his death in 1907, it was proved that the atom consists of elementary particles. The theory of the structure of the atom confirmed the correctness of Mendeleev, the permutations of these elements not in accordance with the growth of atomic masses are fully justified.
The modern formulation of the periodic law.
The properties of chemical elements and their compounds are in a periodic dependence on the magnitude of the charge of the nuclei of their atoms, which is expressed in the periodic repetition of the structure of the outer valence electron shell.
And now, more than 130 years after the discovery of the periodic law, we can return to the words of Dmitry Ivanovich, taken as the motto of our lesson: "The future does not threaten the periodic law with destruction, but only a superstructure and development are promised." How many chemical elements have been discovered so far? And this is far from the limit.
The graphic representation of the periodic law is the periodic system of chemical elements. This is a brief synopsis of the entire chemistry of the elements and their compounds.
Changes in properties in the periodic system with an increase in the value of atomic weights in the period (from left to right):
1. Metallic properties decrease
2. Non-metallic properties increase
3. The properties of higher oxides and hydroxides change from basic through amphoteric to acidic.
4. The valence of elements in the formulas of higher oxides increases from IbeforeVII, and in the formulas of volatile hydrogen compounds decreases from IV beforeI.
Basic principles of construction of the periodic system.|
Comparison sign |
D.I. Mendeleev |
|
1. How is the sequence of elements by numbers established? (What is the basis of PS?) |
The elements are listed in order of increasing relative atomic masses. However, there are exceptions. Ar - K, Co - Ni, Te - I, Th - Pa |
|
2. The principle of combining elements into groups. |
Quality mark. The similarity of the properties of simple substances and the same type of complex. |
|
3. The principle of combining elements into periods. |
The properties of chemical elements and their compounds are in a periodic dependence on the magnitude of the charge of the nuclei of their atoms, which is expressed in the periodic repetition of the structure of the outer valence electron shell.
And now, more than 130 years after the discovery of the periodic law, we can return to the words of Dmitry Ivanovich, taken as the motto of our lesson: "The future does not threaten the periodic law with destruction, but only a superstructure and development are promised." How many chemical elements have been discovered so far? And this is far from the limit.
The graphic representation of the periodic law is the periodic system of chemical elements. This is a brief synopsis of the entire chemistry of the elements and their compounds.
Changes in properties in the periodic system with an increase in the value of atomic weights in the period (from left to right):
1. Metallic properties decrease
2. Non-metallic properties increase
3. The properties of higher oxides and hydroxides change from basic through amphoteric to acidic.
4. The valency of elements in the formulas of higher oxides increases from I to VII, and in the formulas of volatile hydrogen compounds it decreases from IV to I.
Basic principles of construction of the periodic system.
| Basic principles of construction of the periodic system. Comparison sign | D.I. Mendeleev | Current state |
| 1. How is the sequence of elements by numbers established? (What is the basis of ps?) 2. The principle of combining elements into groups. 3. The principle of combining elements into periods. | The elements are listed in order of increasing relative atomic masses. However, there are exceptions. Quality mark. The similarity of the properties of simple substances and the same type of complex. The collection of elements as their relative atomic mass increases from one alkali metal to another. | Elements are arranged as the charge of the nuclei of their atoms increases. There are no exceptions. Quantitative sign. The similarity of the structure of the outer shell. Periodic repetition of the structure of the outer shell determines the similarity of chemical properties. Each new period begins with the appearance of a new electron layer with one electron. And it is always an alkali metal. |
The graphic representation of the periodic law is the periodic table. It contains 7 periods and 8 groups.
1. Ordinal number of a chemical element- the number given to the element when it is numbered. Shows the total number of electrons in an atom and the number of protons in the nucleus, determines the charge of the nucleus of an atom of a given chemical element.
2. Period- chemical elements arranged in a line (there are 7 periods in total). The period determines the number of energy levels in an atom.
Small periods (1 - 3) include only s- and p-elements (elements of the main subgroups) and consist of one line; large (4 - 7) include not only s- and p-elements (elements of the main subgroups), but also d- and f-elements (elements of secondary subgroups) and consist of two lines.
3. Groups- chemical elements arranged in a column (only 8 groups). The group determines the number of outer level electrons for the elements of the main subgroups, as well as the number of valence electrons in an atom of a chemical element.
Main subgroup (A)– includes elements of large and small periods (only s- and p-elements).
Side subgroup (B)– includes elements of only large periods (only d- or f-elements).
Statement of the atomic-molecular theory at the turn of the XVIII-XIX centuries. accompanied by a rapid increase in the number of known chemical elements. Only in the first decade of the nineteenth century 14 new elements were discovered. The English chemist G. Davy (1778–1829) obtained six new elements by electrolysis in one year – sodium, potassium, magnesium, calcium, strontium, and barium. By 1830, the number of known elements reached 55.
The existence of such a number of elements, very diverse in properties, puzzled chemists and required systematization of the elements. Some scientists, noticing the similarities of several elements, combined them into separate groups, but the reasons for the noticeable change in properties were not established. Periodic law of chemical elements- the fundamental law of nature - was discovered by the great Russian chemist D.I. Mendeleev in 1869 as a result of the systematization of chemical elements depending on their atomic weights: the properties of simple bodies, as well as the forms and properties of the compounds of elements, are in a periodic dependence on the magnitude of the atomic weights of the elements.
Despite the enormous significance of Mendeleev's discovery, it was only a brilliant empirical generalization of facts, and their physical meaning remained incomprehensible for a long time. The reason was that in the nineteenth century there was no idea about the complex structure of the atom. Mendeleev himself wrote about this: “The periodic changeability of simple and complex bodies is subject to some higher law, the nature of which, and even more so the cause, there are no means to cover yet. In all likelihood, it lies in the basic principles of the internal mechanics of atoms and particles.”
Data on the structure of the atomic nucleus and the distribution of electrons in atoms allow us to consider the periodic law in a new way, which in its modern formulation reads: the properties of simple substances, as well as the forms and properties of compounds of elements, are in a periodic dependence on the charge of the nucleus of atoms (serial number).
Such a formulation of the law does not contradict the formulation given by Mendeleev. It is only based on new data that give the law physical validity and confirm its correctness. Examples illustrating the manifestation of the periodic law of chemical elements can be the periodic dependence of the density of simple substances in the solid state on the serial number of the element (nucleus charge), or such characteristics of an atom as its size, ionization energy, electronegativity, oxidation state, which have a periodic dependence on the charge atomic nucleus ( rice. 4.3).
The tabular form of the representation of the periodic law is periodic table of chemical elements, developed by Mendeleev in 1869–1871.
Rice. 4.3.Dependence of the density of simple substances in the solid state on the serial number.
In the periodic system of chemical elements, all currently known chemical elements are arranged in ascending order of the charges of their atomic nuclei, numerically equal to the ordinal number of the element, and form 7 horizontal periods, each of which, with the exception of the first, begins with an alkali metal and ends with an inert gas, moreover , the seventh period is incomplete. The first three periods, consisting of one row, are called small, the rest - large.
Vertically, chemical elements are arranged in 8 vertical columns-groups, and each group is divided into two subgroups - the main one, consisting of elements of the second and third periods and similar elements of large periods, and the secondary one, consisting of metals of large periods. Separately, at the bottom of the table are placed elements with serial numbers 58–71, called lanthanides, and elements with serial numbers 90–103, called actinides. In each cell of the periodic system of chemical elements, in addition to the name of the element and its serial number, the value of the relative atomic mass of the element is given and the distribution of electrons by energy levels is shown ( rice. 4.4).
Rice. 4.4. Fragment of the periodic system of chemical elements.
Based on the periodic law of chemical elements and the periodic table, Mendeleev came to the conclusion about the existence of new elements, the properties of which he described in detail and gave them the conventional names - ekabor, ekaaluminum and ekasilicon. Mendeleev's predictions were brilliantly confirmed - all three elements were discovered and received the names of those countries where discoveries were made and minerals containing these elements were found: gallium,scandium,germanium. Thus, Mendeleev carried out a brilliant theoretical analysis of a huge amount of experimental data, synthesized his results in the form of a general law and made predictions based on it, which were soon confirmed experimentally. This work is a classic example of a scientific approach to understanding the world around us.
Periodic Law- the basic law of chemistry - was discovered in 1869 year DI. Mendeleev. At that time, the atom was still considered indivisible and nothing was known about its internal structure.
atomic masses(Then - atomic weights) and the chemical properties of the elements were the basis Periodic law D.I. Mendeleev. DI. Mendeleev, arranging the 63 elements known at that time in ascending order of their atomic masses, obtained natural (natural) series of chemical elements, where he noted the periodic recurrence of chemical properties. For example, a typical non-metal fluorine F repeated for elements chlorine Cl, bromine Br, iodine I, typical metal properties lithium Li - at the elements sodium Na And potassium K etc.
For some elements D.I. Mendeleev found no chemical analogues (in aluminum Al And silicon Si, for example), in view of the fact that at that time such analogues were not yet known. In the table they were intended empty spaces, But based on recurrence scientist predicted their chemical properties). After the discovery of the corresponding elements of the prediction, D.I. Mendeleev were fully confirmed (analogous to aluminum - gallium Ga, silicon analogue - germanium Ge).
The periodic law in the formulation of D.I. Mendeleev is presented as follows: the properties of simple bodies, as well as the forms and properties of compounds of elements, are periodically dependent on the magnitude of the atomic weights of elements.
The modern formulation of the Periodic Law by D.I. Mendeleev is as follows: the properties of the elements are in a periodic dependence on the ordinal number.
Periodic law D.I. Mendeleev became the basis for the creation of scientists Periodic system of chemical elements. It is represented 7 periods and 8 groups.
periods called the horizontal rows of the table, which are divided into small and large. 2 elements (1st period) or 8 elements (2nd, 3rd periods) are in small periods, and 18 elements (4th, 5th periods) or 32 elements (6th period), the 7th period is still incomplete. Every period starts with a typical metal from ends with a typical non-metal and a noble gas.
groups elements are called vertical columns. Each group is represented by two subgroups - main And side. A subgroup is a set of elements that are complete chemical analogues; often the elements of a subgroup have the highest oxidation state corresponding to the group number. For example, the highest oxidation state (+ II) corresponds to the elements of the subgroup beryllium And zinc(the main and secondary subgroups of group II), and the elements of the subgroup nitrogen And vanadium(V group) corresponds to the highest degree of oxidation (+ V).
The chemical properties of elements in the main subgroups can vary from non-metallic to metallic (in the main subgroup of group V, nitrogen is a non-metal, and bismuth is a metal) - in a wide range. The properties of elements in secondary subgroups change, but not so sharply; for example, elements of the side group of group IV - zirconium, titanium, hafnium- very similar in their properties (especially zirconium And hafnium).
In the Periodic system in group I (Li-Fr), II (Mg-Ra) and III (In, Tl) typical metals are located. Non-metals are located in groups VII (F-At), VI (O–Te), V (N - As), IV (C, Si) and III (B). Some elements of the main groups ( Be, Al, Ge, Sb, Po), as well as many elements of the side groups can exhibit both metallic and non-metallic properties. This phenomenon has been named amphotericity.
For some main groups apply groups 
New names: VIII (Not - Rn) - noble gases, VII (F-At) – halogens, IV (O - Ro) - chalcogens, II (Са – Ra) – alkaline earth metals, I (Li – Fr) – alkali metals.
The form of the Periodic system, which was proposed by D.I. Mendeleev, was named short-term, or classical. In modern chemistry, another form is increasingly used - long period, in which all periods - small and large - are elongated in long rows, starting with an alkali metal and ending with a noble gas.
Periodic law D.I. Mendeleev and the Periodic system of elements of D.I. Mendeleev became the basis of modern chemistry.
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