The history of the creation of the periodic table of chemical elements. The history of the discovery of the periodic law and the periodic system of elements. The principle of organization of the periodic table

2.2. History of the creation of the Periodic Table.

In the winter of 1867-68, Mendeleev began writing the textbook “Fundamentals of Chemistry” and immediately encountered difficulties in systematizing the factual material. By mid-February 1869, while pondering the structure of the textbook, he gradually came to the conclusion that the properties simple substances(and this is a form of existence chemical elements in a free state) and the atomic masses of elements are connected by a certain pattern.

Mendeleev did not know much about the attempts of his predecessors to arrange chemical elements in order of increasing atomic masses and about the incidents that arose in this case. For example, he had almost no information about the work of Chancourtois, Newlands and Meyer.

The decisive stage of his thoughts came on March 1, 1869 (February 14, old style). A day earlier, Mendeleev wrote a request for leave for ten days to examine artel cheese dairies in the Tver province: he received a letter with recommendations for studying cheese production from A. I. Khodnev, one of the leaders of Volny economic society.

In St. Petersburg that day it was cloudy and frosty. The trees in the university garden, where the windows of Mendeleev’s apartment overlooked, creaked in the wind. While still in bed, Dmitry Ivanovich drank a mug of warm milk, then got up, washed his face and went to breakfast. He was in a wonderful mood.

At breakfast, Mendeleev had an unexpected idea: to compare the similar atomic masses of various chemical elements and their chemical properties. Without thinking twice, on the back of Khodnev’s letter he wrote down the symbols for chlorine Cl and potassium K with fairly close atomic masses, equal to 35.5 and 39, respectively (the difference is only 3.5 units). On the same letter, Mendeleev sketched symbols of other elements, looking for similar “paradoxical” pairs among them: fluorine F and sodium Na, bromine Br and rubidium Rb, iodine I and cesium Cs, for which the mass difference increases from 4.0 to 5.0 , and then up to 6.0. Mendeleev could not have known then that the “indefinite zone” between obvious non-metals and metals contained elements - noble gases, the discovery of which would subsequently significantly modify the Periodic Table.

After breakfast, Mendeleev locked himself in his office. He took out a stack of business cards from the desk and began writing on the back of them the symbols of the elements and their main chemical properties. After some time, the household heard the sound coming from the office: “Oooh! Horned one. Wow, what a horned one! I’ll defeat them. I’ll kill them!” These exclamations meant that Dmitry Ivanovich had creative inspiration. Mendeleev moved cards from one horizontal row to another, guided by the values of atomic mass and the properties of simple substances formed by atoms of the same element. Once again, thorough knowledge came to his aid inorganic chemistry. Gradually, the shape of the future Periodic Table of Chemical Elements began to emerge. So, first he put a card with the element beryllium Be ( atomic mass 14) next to the card of the aluminum element Al (atomic mass 27.4), according to the then tradition, mistaking beryllium for an analogue of aluminum. However, then, after comparing the chemical properties, he placed beryllium over magnesium Mg. Doubting the then generally accepted value of the atomic mass of beryllium, he changed it to 9.4, and changed the formula of beryllium oxide from Be 2 O 3 to BeO (like magnesium oxide MgO). By the way, the “corrected” value of the atomic mass of beryllium was confirmed only ten years later. He acted just as boldly on other occasions.

Gradually, Dmitry Ivanovich came to the final conclusion that elements arranged in increasing order of their atomic masses exhibit a clear periodicity of physical and chemical properties. Throughout the day, Mendeleev worked on the system of elements, breaking off briefly to play with his daughter Olga and have lunch and dinner.

On the evening of March 1, 1869, he completely rewrote the table he had compiled and, under the title “Experience of a system of elements based on their atomic weight and chemical similarity,” sent it to the printing house, making notes for typesetters and putting the date “February 17, 1869” (this is the old style).

This is how the Periodic Law was discovered, the modern formulation of which is as follows: The properties of simple substances, as well as the forms and properties of compounds of elements, are periodically dependent on the charge of the nuclei of their atoms.

Mendeleev sent printed sheets with the table of elements to many domestic and foreign chemists and only after that left St. Petersburg to inspect cheese factories.

Before leaving, he still managed to hand over to N.A. Menshutkin, an organic chemist and future historian of chemistry, the manuscript of the article “Relationship of properties with the atomic weight of elements” - for publication in the Journal of the Russian Chemical Society and for communication at the upcoming meeting of the society.

On March 18, 1869, Menshutkin, who was the company's clerk at that time, made a short report on the Periodic Law on behalf of Mendeleev. The report at first did not attract much attention from chemists, and the President of the Russian Chemical Society, Academician Nikolai Zinin (1812-1880) stated that Mendeleev was not doing what a real researcher should do. True, two years later, after reading Dmitry Ivanovich’s article “The Natural System of Elements and Its Application to Indicating the Properties of Some Elements,” Zinin changed his mind and wrote to Mendeleev: “Very, very good, very excellent connections, even fun to read, God grant you good luck in experimental confirmation of your conclusions. Your sincerely devoted and deeply respectful N. Zinin." Mendeleev did not place all elements in order of increasing atomic masses; in some cases he was more guided by the similarity of chemical properties. Thus, the atomic mass of cobalt Co is greater than that of nickel Ni, and tellurium Te is also greater than that of iodine I, but Mendeleev placed them in the order Co - Ni, Te - I, and not vice versa. Otherwise, tellurium would fall into the halogen group, and iodine would become a relative of selenium Se.

To my wife and children. Or maybe he knew that he was dying, but did not want to disturb and worry the family in advance, whom he loved warmly and tenderly.” At 5:20 a.m. On January 20, 1907, Dmitry Ivanovich Mendeleev died. He was buried at the Volkovskoye cemetery in St. Petersburg, not far from the graves of his mother and son Vladimir. In 1911, on the initiative of advanced Russian scientists, the D.I. Museum was organized. Mendeleev, where...

Moscow metro station, research vessel for oceanographic research, 101st chemical element and mineral - mendeleevite. Russian-speaking scientists and jokers sometimes ask: “Isn’t Dmitry Ivanovich Mendeleev a Jew, that’s a very strange surname, didn’t it come from the surname “Mendel”?” The answer to this question is extremely simple: “All four sons of Pavel Maksimovich Sokolov, ...

The lyceum exam, at which old Derzhavin blessed young Pushkin. The role of the meter happened to be played by Academician Yu.F. Fritzsche, a famous specialist in organic chemistry. Candidate's thesis D.I. Mendeleev graduated from the Main Pedagogical Institute in 1855. His thesis "Isomorphism in connection with other relationships of crystalline form to composition" became his first major scientific...

Mainly on the issue of capillarity and surface tension of liquids, and spent his leisure hours in the circle of young Russian scientists: S.P. Botkina, I.M. Sechenova, I.A. Vyshnegradsky, A.P. Borodin and others. In 1861, Mendeleev returned to St. Petersburg, where he resumed lecturing on organic chemistry at the university and published a textbook that was remarkable for that time: " Organic chemistry", V...

The establishment of the atomic-molecular theory at the turn of the 19th - 19th centuries was accompanied by a rapid increase in the number of known chemical elements. In the first decade of the 19th century alone, 14 new elements were discovered. The record holder among the discoverers was the English chemist Humphry Davy, who in one year using electrolysis obtained 6 new simple substances (sodium, potassium, magnesium, calcium, barium, strontium). And by 1830, the number of known elements reached 55.

The existence of such a number of elements, heterogeneous in their properties, puzzled chemists and required ordering and systematization of the elements. Many scientists searched for patterns in the list of elements and achieved some progress. There are three most significant works that challenged the priority of discovery periodic law at D.I. Mendeleev.

Mendeleev formulated the periodic law in the form of the following basic principles:

1. Elements arranged according to atomic weight represent a clear periodicity of properties.
2. We should expect the discovery of many more unknown simple bodies, for example, elements similar to Al and Si with an atomic weight of 65 - 75.
3. The atomic weight of an element can sometimes be corrected by knowing its analogues.

Some analogies are revealed by the size of the weight of their atom. The first position was known even before Mendeleev, but it was he who gave it the character of a universal law, predicting on its basis the existence of elements that had not yet been discovered, changing the atomic weights of a number of elements and arranging some elements in the table contrary to their atomic weights, but in full accordance with their properties (mainly by valency). The remaining provisions were discovered only by Mendeleev and are logical consequences of the periodic law. The correctness of these consequences was confirmed by many experiments over the next two decades and made it possible to speak of the periodic law as a strict law of nature.

Using these provisions, Mendeleev compiled his own version of the periodic table of elements. The first draft of the table of elements appeared on February 17 (March 1, new style) 1869.

And on March 6, 1869, Professor Menshutkin made an official announcement about Mendeleev’s discovery at a meeting of the Russian Chemical Society.

The following confession was put into the mouth of the scientist: I see in a dream a table where all the elements are arranged as needed. I woke up and immediately wrote it down on a piece of paper - only in one place did a correction later turn out to be necessary.” How simple everything is in legends! It took more than 30 years of the scientist’s life to develop and correct it.

The process of discovering the periodic law is instructive and Mendeleev himself spoke about it this way: “The idea involuntarily arose that between mass and chemical properties there must be a connection.

And since the mass of a substance, although not absolute, but only relative, is ultimately expressed in the form of atomic weights, it is necessary to look for a functional correspondence between the individual properties of elements and their atomic weights. You can’t look for anything, even mushrooms or some kind of addiction, except by looking and trying.

So I began to select, writing on separate cards elements with their atomic weights and fundamental properties, similar elements and similar atomic weights, which quickly led to the conclusion that the properties of elements are periodically dependent on their atomic weight, and, doubting many ambiguities, I did not doubt for a minute the generality of the conclusion drawn, since it is impossible to allow accidents.”

In the very first periodic table, all elements up to and including calcium are the same as in the modern table, with the exception of the noble gases. This can be seen from a fragment of a page from an article by D.I. Mendeleev, containing the periodic table of elements.

Based on the principle of increasing atomic weights, the next elements after calcium should have been vanadium, chromium and titanium. But Mendeleev put a question mark after calcium, and then placed titanium, changing its atomic weight from 52 to 50.

The unknown element, indicated by a question mark, was assigned an atomic weight A = 45, which is the arithmetic mean between the atomic weights of calcium and titanium. Then, between zinc and arsenic, Mendeleev left room for two elements that had not yet been discovered. In addition, he placed tellurium in front of iodine, although the latter has a lower atomic weight. With this arrangement of elements, all horizontal rows in the table contained only similar elements, and the periodicity of changes in the properties of the elements was clearly evident. Over the next two years, Mendeleev significantly improved the system of elements. In 1871, the first edition of Dmitry Ivanovich’s textbook “Fundamentals of Chemistry” was published, which presented the periodic system in an almost modern form.

In the table, 8 groups of elements were formed, the group numbers indicate the highest valence of the elements of those series that are included in these groups, and the periods become closer to modern ones, divided into 12 series. Now each period begins with an active alkali metal and ends with a typical non-metal halogen. The second version of the system made it possible for Mendeleev to predict the existence of not 4, but 12 elements and, challenging the scientific world, with amazing accuracy he described the properties of three unknown elements, which he called ekabor (eka on Sanskrit means “one and the same”), eka-aluminum and eka-silicon. (Gaul is the ancient Roman name for France). The scientist managed to isolate this element in its pure form and study its properties. And Mendeleev saw that the properties of gallium coincided with the properties of eka-aluminium, which he predicted, and told Lecoq de Boisbaudran that he incorrectly measured the density of gallium, which should be equal to 5.9-6.0 g/cm3 instead of 4.7 g/cm3. Indeed, more careful measurements led to the correct value of 5.904 g/cm3. Final recognition of the periodic law of D.I. Mendeleev was achieved after 1886, when the German chemist K. Winkler, analyzing silver ore, obtained an element that he called germanium. It turns out to be ecasilicon.

Periodic law and periodic system of elements.

The periodic law is one of the most important laws of chemistry. Mendeleev believed that main characteristic of an element is its atomic mass. Therefore, he arranged all the elements in one row in order of increasing atomic mass.

If we consider a number of elements from Li to F, we can see that the metallic properties of the elements are weakened, and the non-metallic properties are enhanced. The properties of elements in the series from Na to Cl change similarly. The next sign K, like Li and Na, is a typical metal.

The highest valence of elements increases from I y Li to V y N (oxygen and fluorine have a constant valency, II and I, respectively) and from I y Na to VII y Cl. The next element K, like Li and Na, has a valence of I. In the series of oxides from Li2O to N2O5 and hydroxides from LiOH to HNO3, the basic properties are weakened, and acid properties are intensifying. The properties of oxides change similarly in the series from Na2O and NaOH to Cl2O7 and HClO4. Potassium oxide K2O, like the lithium and sodium oxides Li2O and Na2O, is a basic oxide, and potassium hydroxide KOH, like lithium and sodium hydroxides LiOH and NaOH, is a typical base.

The forms and properties of nonmetals change similarly from CH4 to HF and from SiH4 to HCl.

This character of the properties of elements and their compounds, which is observed with an increase in the atomic mass of elements, is called periodic change. The properties of all chemical elements change periodically with increasing atomic mass.

This periodic change is called the periodic dependence of the properties of elements and their compounds on the atomic mass.

Therefore D.I. Mendeleev formulated the law he discovered as follows:

· The properties of elements, as well as the forms and properties of compounds of elements, are periodically dependent on the atomic mass of the elements.

Mendeleev arranged the periods of the elements one below the other and as a result compiled the periodic table of the elements.

He said that the table of elements was the fruit not only of his own work, but also of the efforts of many chemists, among whom he especially noted the “strengtheners of the periodic law” who discovered the elements he predicted.

Creating a modern table required many years of hard work by thousands and thousands of chemists and physicists. If Mendeleev were alive today, looking at the modern table of elements, he could well repeat the words of the English chemist J. W. Mellor, author of the classic 16-volume encyclopedia on inorganic and theoretical chemistry. Having finished his work in 1937, after 15 years of work, he wrote with gratitude on the title page: “Dedicated to the privates of a huge army of chemists. Their names are forgotten, their works remain...

The periodic system is a classification of chemical elements that establishes the dependence of various properties of elements on the charge of the atomic nucleus. The system is a graphic expression of the periodic law. As of October 2009, 117 chemical elements are known (with serial numbers from 1 to 116 and 118), of which 94 are found in nature (some only in trace quantities). The rest23 were obtained artificially as a result of nuclear reactions - this is the process of transformation of atomic nuclei that occurs during their interaction with elementary particles, gamma rays and with each other, usually leading to the release of colossal amounts of energy. The first 112 elements have permanent names, the rest have temporary names.

The discovery of element 112 (the heaviest of the official ones) is recognized by the International Union of Pure and Applied Chemistry.

The most stable known isotope of this element has a half-life of 34 seconds. At the beginning of June 2009, it bears the unofficial name of ununbium; it was first synthesized in February 1996 at the heavy ion accelerator at the Heavy Ion Institute in Darmstadt. Discoverers have six months to propose a new official name to add to the table (they have already proposed Wickhausius, Helmholtzius, Venusius, Frischius, Strassmannius and Heisenbergius). Currently, transuranic elements with numbers 113-116 and 118 are known, obtained at the Joint Institute for Nuclear Research in Dubna, but they have not yet been officially recognized. More common than others are 3 forms of the periodic table: “short” (short-period), “long” (long-period) and “extra-long”. In the “super-long” version, each period occupies exactly one line. In the “long” version, the lanthanides (a family of 14 chemical elements with serial numbers 58-71, located in the VI period of the system) and actinides (a family of radioactive chemical elements consisting of actinium and 14 similar to it in their chemical properties) are removed from the general table , making it more compact. In the “short” form of recording, in addition to this, the fourth and subsequent periods occupy 2 lines each; The symbols of the elements of the main and secondary subgroups are aligned relative to different edges of the cells. The short form of the table, containing eight groups of elements, was officially abandoned by IUPAC in 1989. Despite the recommendation to use the long form, the short form continued to be large number Russian reference books and manuals even after this time. From modern foreign literature, the short form is completely excluded, and the long form is used instead. Some researchers associate this situation, among other things, with the apparent rational compactness of the short form of the table, as well as with stereotypical thinking and non-perception of modern (international) information.

In 1969, Theodore Seaborg proposed an extended periodic table of the elements. Niels Bohr developed the ladder (pyramidal) form of the periodic table.

There are many other, rarely or not used at all, but very original, ways of graphically displaying the Periodic Law. Today, there are several hundred versions of the table, and scientists are constantly offering new options.

Periodic law and its rationale.

The periodic law made it possible to systematize and generalize a huge amount of scientific information in chemistry. This function of the law is usually called integrative. It is especially clearly manifested in the structuring of scientific and educational material chemistry.

Academician A.E. Fersman said that the system united all chemistry within a single spatial, chronological, genetic, and energetic connection.

The integrative role of the Periodic Law was also manifested in the fact that some data on elements that allegedly fell out of general patterns, were checked and clarified by both the author himself and his followers.

This happened with the characteristics of beryllium. Before Mendeleev's work, it was considered a trivalent analogue of aluminum due to their so-called diagonal similarity. Thus, in the second period there were two trivalent elements and not a single divalent one. It was at this stage that Mendeleev suspected an error in the research into the properties of beryllium; he found the work of the Russian chemist Avdeev, who argued that beryllium was divalent and had an atomic weight of 9. Avdeev's work remained unnoticed scientific world, the author died early, apparently having been poisoned by extremely poisonous beryllium compounds. The results of Avdeev’s research were established in science thanks to the Periodic Law.

Such changes and refinements of the values of both atomic weights and valences were made by Mendeleev for nine more elements (In, V, Th, U, La, Ce and three other lanthanides).

For ten more elements, only atomic weights were corrected. And all these clarifications were subsequently confirmed experimentally.

The prognostic (predictive) function of the Periodic Law received the most striking confirmation in the discovery of unknown elements with serial numbers 21, 31 and 32.

Their existence was first predicted intuitively, but with the formation of the system, Mendeleev was able to calculate their properties with a high degree of accuracy. Fine famous story The discovery of scandium, gallium and germanium was a triumph of Mendeleev's discovery. He made all his predictions on the basis of the universal law of nature that he himself discovered.

In total, Mendeleev predicted twelve elements. From the very beginning, Mendeleev pointed out that the law describes the properties not only of the chemical elements themselves, but also of many of their compounds. To confirm this, it is enough to give the following example. Since 1929, when academician P. L. Kapitsa first discovered the non-metallic conductivity of germanium, the development of the study of semiconductors began in all countries of the world.

It immediately became clear that elements with such properties occupy the main subgroup of group IV.

Over time, the understanding came that semiconductor properties should, to a greater or lesser extent, be possessed by compounds of elements located in periods equally distant from this group (for example, with general formula type AzB).

This immediately made the search for new practically important semiconductors targeted and predictable. Almost all modern electronics are based on such connections.

It is important to note that predictions within the Periodic Table were made even after its general acceptance. In 1913

Moseley discovered that the wavelength x-rays, which are obtained from anti-cathodes made from different elements, changes naturally depending on the serial number conventionally assigned to the elements in the Periodic Table. The experiment confirmed that the serial number of an element has a direct physical meaning.

Only later were serial numbers related to the value of the positive charge of the nucleus. But Moseley’s law made it possible to immediately experimentally confirm the number of elements in the periods and at the same time predict the places of hafnium (No. 72) and rhenium (No. 75) that had not yet been discovered by that time.

For a long time there was a debate: to allocate inert gases into an independent zero group of elements or to consider them as the main subgroup of group VIII.

Based on the position of the elements in the Periodic Table, theoretical chemists led by Linus Pauling have long doubted the complete chemical passivity of noble gases, directly pointing to the possible stability of their fluorides and oxides.

But only in 1962, the American chemist Neil Bartlett was the first to carry out the reaction of platinum hexafluoride with oxygen under the most ordinary conditions, obtaining xenon hexafluoroplatinate XePtF^, followed by other gas compounds that are now more correctly called noble rather than inert.

In the winter of 1867-68, Mendeleev began writing the textbook “Fundamentals of Chemistry” and immediately encountered difficulties in systematizing the factual material. By mid-February 1869, pondering the structure of the textbook, he gradually came to the conclusion that the properties of simple substances (and this is the form of existence of chemical elements in a free state) and the atomic masses of elements are connected by a certain pattern.

At breakfast, Mendeleev had an unexpected idea: to compare the similar atomic masses of various chemical elements and their chemical properties.

Without thinking twice, on the back of Khodnev’s letter he wrote down the symbols for chlorine Cl and potassium K with fairly close atomic masses, equal to 35.5 and 39, respectively (the difference is only 3.5 units). On the same letter, Mendeleev sketched symbols of other elements, looking for similar “paradoxical” pairs among them: fluorine F and sodium Na, bromine Br and rubidium Rb, iodine I and cesium Cs, for which the mass difference increases from 4.0 to 5.0 , and then up to 6.0. Mendeleev could not have known then that the “indefinite zone” between obvious non-metals and metals contained elements - noble gases, the discovery of which would subsequently significantly modify the Periodic Table.

After some time, the household heard the sound coming from the office: “Uh-oh! Horned. Wow, what a horned one! I’ll defeat them. I’ll kill them!” These exclamations meant that Dmitry Ivanovich had creative inspiration.

Mendeleev moved cards from one horizontal row to another, guided by the values of atomic mass and the properties of simple substances formed by atoms of the same element. Once again, a thorough knowledge of inorganic chemistry came to his aid. Gradually, the shape of the future Periodic Table of Chemical Elements began to emerge.

So, at first he put a card with the element beryllium Be (atomic mass 14) next to a card with the element aluminum Al (atomic mass 27.4), according to the then tradition, mistaking beryllium for an analogue of aluminum. However, then, after comparing the chemical properties, he placed beryllium over magnesium Mg. Doubting the then generally accepted value of the atomic mass of beryllium, he changed it to 9.4, and changed the formula of beryllium oxide from Be2O3 to BeO (like magnesium oxide MgO). By the way, the “corrected” value of the atomic mass of beryllium was confirmed only ten years later. He acted just as boldly on other occasions.

Gradually, Dmitry Ivanovich came to the final conclusion that elements arranged in increasing order of their atomic masses exhibit a clear periodicity of physical and chemical properties.

Throughout the day, Mendeleev worked on the system of elements, breaking off briefly to play with his daughter Olga and have lunch and dinner.

This is how the Periodic Law was discovered, the modern formulation of which is as follows: “The properties of simple substances, as well as the forms and properties of compounds of elements, are periodically dependent on the charge of the nuclei of their atoms.”

Mendeleev was only 35 years old at that time.

Mendeleev sent printed sheets with the table of elements to many domestic and foreign chemists and only after that left St. Petersburg to inspect cheese factories.

After the discovery of the Periodic Law, Mendeleev had much more to do. The reason for the periodic change in the properties of the elements remained unknown, and the structure of the Periodic System itself, where the properties were repeated through seven elements at the eighth, could not be explained. However, the first veil of mystery was removed from these numbers: in the second and third periods of the system there were then just seven elements.

Mendeleev did not place all elements in order of increasing atomic masses; in some cases he was more guided by the similarity of chemical properties. Thus, the atomic mass of cobalt Co is greater than that of nickel Ni, and tellurium Te is also greater than that of iodine I, but Mendeleev placed them in the order Co - Ni, Te - I, and not vice versa. Otherwise, tellurium would fall into the halogen group, and iodine would become a relative of selenium Se.

The most important thing in the discovery of the Periodic Law is the prediction of the existence of chemical elements that have not yet been discovered. Under aluminum Al, Mendeleev left a place for its analogue “eka-aluminium”, under boron B - for “eca-boron”, and under silicon Si - for “eca-silicon”. This is what Mendeleev called the yet undiscovered chemical elements. He even gave them the symbols El, Eb and Es.

Regarding the element “exasilicon,” Mendeleev wrote: “It seems to me that the most interesting of the undoubtedly missing metals will be the one that belongs to the IV group of carbon analogues, namely, to the III row. This will be the metal immediately following silicon, and therefore we will call his ekasilicium." Indeed, this not yet discovered element was supposed to become a kind of “lock” connecting two typical non-metals - carbon C and silicon Si - with two typical metals - tin Sn and lead Pb.

Not all foreign chemists immediately appreciated the significance of Mendeleev’s discovery. It changed a lot in the world of established ideas. Thus, the German physical chemist Wilhelm Ostwald, future laureate Nobel Prize, argued that it was not the law that was discovered, but the principle of classification of “something uncertain.” The German chemist Robert Bunsen, who discovered two new alkali elements, rubidium Rb and cesium Cs, in 1861, wrote that Mendeleev carried chemists “into the far-fetched world of pure abstractions.”

Leipzig University professor Hermann Kolbe called Mendeleev's discovery "speculative" in 1870. Kolbe was distinguished by his rudeness and rejection of new theoretical views in chemistry. In particular, he was an opponent of the theory of structure organic compounds and at one time sharply attacked Jacob van't Hoff's article "Chemistry in Space". Van't Hoff later became the first for his research Nobel laureate. But Kolbe proposed that researchers such as Van't Hoff "exclude from the ranks of real scientists and enroll them in the camp of spiritualists"!

Every year the Periodic Law won more and more supporters, and its discoverer gained more and more recognition. High-ranking visitors began to appear in Mendeleev's laboratory, including even Grand Duke Konstantin Nikolaevich, manager of the maritime department.

The discovery of the periodic table of chemical elements by Dmitri Mendeleev in March 1869 was a real breakthrough in chemistry. The Russian scientist managed to systematize knowledge about chemical elements and present them in the form of a table, which schoolchildren are still required to study in chemistry lessons. The periodic table became the foundation for the rapid development of this complex and interesting science, and the history of its discovery is shrouded in legends and myths. For all those interested in science, it will be interesting to know the truth about how Mendeleev discovered the table periodic elements.

History of the periodic table: how it all began

Attempts to classify and systematize known chemical elements were made long before Dmitry Mendeleev. Such famous scientists as Döbereiner, Newlands, Meyer and others proposed their systems of elements. However, due to a lack of data on chemical elements and their correct atomic masses, the proposed systems were not entirely reliable.

The history of the discovery of the periodic table begins in 1869, when a Russian scientist at a meeting of the Russian Chemical Society told his colleagues about his discovery. In the table proposed by the scientist, chemical elements were arranged depending on their properties, ensured by the size of their molecular weight.

An interesting feature of the periodic table was also the presence of empty cells, which in the future were filled with open chemical elements predicted by the scientist (germanium, gallium, scandium). Since the discovery of the periodic table, additions and amendments have been made to it many times. Together with the Scottish chemist William Ramsay, Mendeleev added a group of inert gases (group zero) to the table.

Subsequently, the history of Mendeleev's periodic table was directly related to discoveries in another science - physics. Work on the table of periodic elements continues to this day, and modern scientists add new chemical elements as they are discovered. The importance of Dmitry Mendeleev’s periodic system is difficult to overestimate, since thanks to it:

Knowledge about the properties of already discovered chemical elements was systematized;
It became possible to predict the discovery of new chemical elements;
Such branches of physics as atomic physics and nuclear physics began to develop;

There are many options for depicting chemical elements according to the periodic law, but the most famous and common option is the periodic table familiar to everyone.

Myths and facts about the creation of the periodic table

The most common misconception in the history of the discovery of the periodic table is that the scientist saw it in a dream. In fact, Dmitri Mendeleev himself refuted this myth and stated that he had been pondering the periodic law for many years. To systematize the chemical elements, he wrote out each of them on a separate card and repeatedly combined them with each other, arranging them in rows depending on their similar properties.

The myth about the scientist’s “prophetic” dream can be explained by the fact that Mendeleev worked on the systematization of chemical elements for days on end, interrupted by short sleep. However, only the hard work and natural talent of the scientist gave the long-awaited result and provided Dmitry Mendeleev with worldwide fame.

Many students at school, and sometimes at university, are forced to memorize or at least roughly navigate the periodic table. To do this, a person must not only have a good memory, but also think logically, linking elements into separate groups and classes. Studying the table is easiest for those people who constantly keep their brain in good shape by undergoing training on BrainApps.

Ministry of Education and Science of the Russian Federation

Department of Education of the Administration of Tver

Municipal educational institution

"Evening (shift) comprehensive school No. 2" Tver

Student essay competition "Krugozor"

Abstract on the topic:

The history of the discovery of the Periodic Law and the Periodic Table of Chemical Elements by Dmitry Ivanovich Mendeleev

student of the 8th group of Municipal Educational Institution VSOSH No. 2, Tver

Supervisor:

chemistry teacher of the highest category

Municipal educational institution VSOSH No. 2, Tver

Introduction……………………….................................................. ...................................3

1. Prerequisites for the discovery of the Periodic Law……..4

1.1. Classification………………………………………………………..4

1.2. Döbereiner's triads and the first systems of elements…………………….4

1.3. Spiral de Chancourtois …………………………………………………………..5

1.5.Odling and Meyer tables…………………………………………………………………….7

2. Discovery of the Periodic Law…………………...9

Conclusion…………………………………………………………………. 16

References……………………………………………………….17

Introduction

The periodic law and the periodic table of chemical elements are the basis of modern chemistry.

Mendeleev named cities, factories, educational establishments, research institutes. A gold medal has been approved in Russia in honor - it is awarded for outstanding work in chemistry. The name of the scientist was assigned to the Russian Chemical Society. In honor, Regional Mendeleev Readings are held annually in the Tver region. Even the element with serial number 101 was given the name mendelevium, in honor of Dmitry Ivanovich.

His main merit was the discovery of the periodic law and the creation of the periodic system of chemical elements, which immortalized his name in world science. This law and the periodic system are the basis of everything further development teachings about atoms and elements, they are the foundation of chemistry and physics of our days.

Goal of the work: study the prerequisites for the emergence of the periodic law and the periodic system of chemical elements and evaluate the contribution of Dmitry Ivanovich Mendeleev to this discovery.

1. Prerequisites for the discovery of the Periodic Law

The search for the basis for the natural classification of chemical elements and their systematization began long before the discovery of the Periodic Law. By the time the Periodic Law was discovered, 63 chemical elements were known, and the composition and properties of their compounds were described.

1.1 Classification

The outstanding Swedish chemist divided all elements into metals and non-metals based on differences in the properties of the simple substances and compounds they formed. He determined that metals correspond to basic oxides and bases, and non-metals correspond to acidic oxides and acids.

Table 1. Classification

1.2. Döbereiner triads and the first systems of elements

In 1829, the German chemist Johann Wolfgang Döbereiner made the first significant attempt to systematize the elements. He noticed that some elements with similar properties can be combined in groups of three, which he called triads.

The essence of the proposed law of Döbereiner triads was that the atomic mass of the middle element of the triad was close to half the sum (arithmetic mean) of the atomic masses of the two extreme elements of the triad. Despite the fact that Döbereiner's triads are to some extent prototypes of Mendeleev's groups, these ideas as a whole are still too imperfect. The absence of magnesium in the single family of calcium, strontium and barium or oxygen in the family of sulfur, selenium and tellurium is the result of the artificial limitation of sets of similar elements to only triple unions. Very indicative in this sense is Döbereiner’s failure to isolate a triad of four elements with similar properties: P, As, Sb, Bi. Döbereiner clearly saw deep analogies in the chemical properties of phosphorus and arsenic, antimony and bismuth, but, having previously limited himself to searching for triads, he could not find the right solution. Half a century later, Lothar Mayer would say that if Döbereiner had only briefly distracted himself from his triads, he would have immediately seen the similarity of all these four elements at the same time.

Although Döbereiner, naturally, did not succeed in breaking all known elements into triads, the law of triads clearly indicated the existence of a relationship between atomic mass and the properties of elements and their compounds. All further attempts at systematization were based on the placement of elements in accordance with their atomic masses.

1.3. Spiral de Chancourtois (1862)

Professor of the Paris Higher School Alexandre Beguier de Chancourtois arranged all the chemical elements known at that time in a single sequence of increasing their atomic masses and applied the resulting series to the surface of the cylinder along a line emanating from its base at an angle of 45° to the plane of the base (the so-called earth spiral). When unfolding the surface of the cylinder, it turned out that on vertical lines parallel to the cylinder axis, there were chemical elements with similar properties. So, lithium, sodium, potassium fell on one vertical; beryllium, magnesium, calcium; oxygen, sulfur, selenium, tellurium, etc. The disadvantage of the de Chancourtois spiral was the fact that on the same line with similar chemical nature The elements also turned out to be elements of completely different chemical behavior. Manganese fell into the group of alkali metals, and titanium, which had nothing in common with them, fell into the group of oxygen and sulfur. Thus, for the first time, the idea of the periodicity of the properties of elements was born, but no attention was paid to it, and soon it was forgotten.

Soon after de Chancourtois's spiral, the American scientist John Newlands made an attempt to compare the chemical properties of elements with their atomic masses. Arranging the elements in order of increasing atomic mass, Newlands noticed that similarities in properties appeared between every eighth element. Newlands called the found pattern the law of octaves by analogy with the seven intervals of the musical scale. In his table, he arranged the chemical elements into vertical groups of seven elements each and at the same time discovered that (with a slight change in the order of some elements) elements with similar chemical properties ended up on the same horizontal line. John Newlands was, of course, the first to give a series of elements arranged in order of increasing atomic masses, assign the corresponding atomic number to the chemical elements, and notice the systematic relationship between this order and the physicochemical properties of the elements. He wrote that in such a sequence the properties of elements are repeated, the equivalent weights (mass) of which differ by 7 units, or by a value that is a multiple of 7, i.e., as if the eighth element in order repeats the properties of the first, as in music the eighth note repeats first.

Newlands tried to give this dependence, which actually occurs for light elements, a universal character. In his table, similar elements were located in horizontal rows, but in the same row there were often elements completely different in properties. The London Chemical Society greeted his law of octaves with indifference and suggested that Newlands try to arrange the elements alphabetically and identify any pattern.

1.5. Odling and Meyer tables

Also in 1864, the first table of the German chemist Lothar Meyer appeared; it included 28 elements, arranged in six columns according to their valencies. Meyer deliberately limited the number of elements in the table in order to emphasize the regular (similar to Döbereiner's triads) change in atomic mass in series of similar elements.

Fig. 3. Meyer's table of chemical elements

In 1870, Meyer's work was published containing a new table entitled "The Nature of the Elements as a Function of Their Atomic Weight", consisting of nine vertical columns. Similar elements were located in the horizontal rows of the table; Meyer left some cells blank. The table was accompanied by a graph of the dependence of the atomic volume of an element on the atomic weight, which has a characteristic sawtooth shape, perfectly illustrating the term « periodicity », already proposed by that time by Mendeleev.

2. Discovery of the Periodic Law

There are several stories from close people about how the periodic law was discovered; These stories were transmitted orally by eyewitnesses, then penetrated into the press and became a kind of legends, which have not yet been possible to verify due to the lack of relevant documentary data. The story of a professor of geology in St. Petersburg is interesting. University (), close friend. , who visited just in those days when he discovered the periodic law, gives interesting touches on how he worked on creating his system of elements, who published the story, wrote:

"About the final creative process Mendeleev’s intuition, Emeritus Professor Alexander Aleksandrovich Inostrantsev kindly informed me in highest degree interesting things. Once, already being the secretary of the Faculty of Physics and Mathematics, A.A. came to visit Mendeleev, with whom, as a scientist and close friend, he was in constant spiritual communication. He sees: D.I. standing at the desk, apparently in a gloomy, depressed state.

What are you doing, Dmitry Ivanovich?

Mendeleev started talking about what was later embodied in the periodic system of elements, but at that moment the law and the table had not yet been formed: “Everything came together in my head,” Mendeleev added bitterly, “but I can’t express it in a table.” A little later the following happened. Mendeleev worked at his desk for three days and three nights, without going to bed, trying to combine the results of his mental construction into a table, but attempts to achieve this were unsuccessful. Finally, under the influence of extreme fatigue, Mendeleev went to bed and immediately fell asleep. “In my dream I see a table where the elements are arranged as needed. I woke up and immediately wrote it down on a piece of paper - only in one place did a correction later turn out to be necessary.”

Next, it is necessary to take into account his own testimony in “Fundamentals of Chemistry” about how, when finalizing his classification of elements, he used cards on which data about individual elements were written. The cards were needed precisely to identify a still unknown relationship between elements, and not at all for its final design. And most importantly, as evidenced by the initial draft of the table, the cards with the elements written on them were initially not located in the order of groups and rows (periods), but only in the order of groups (the periods were not yet discovered at first). The groups were placed one below the other, and it was this placement of groups that led to the discovery that the vertical columns (periods) of elements are adjacent to each other, forming a common continuous series of elements in which certain chemical properties are periodically repeated. This, strictly speaking, was the discovery of the periodic law.

Moreover, if the existence not only of groups, but also of periods of elements was already known, then there would be no need to resort to cards for individual elements.

The third story, again told in his own words, comes from a close friend - an outstanding Czech chemist. This story was published by Brauner in 1907. after the death of his great friend; in 1930 it was reprinted in a collection of works of Czechoslovak chemists. During the Second World War, this story was given by Gerald Druce in his biography of Boguslav Brauner. According to Brauner, he told him how the compilation of a chemistry textbook, i.e., “Fundamentals of Chemistry,” helped to discover and formulate the periodic law.

“When I began to write my textbook,” said Brauner, “I felt that a system was needed that would allow me to distribute the chemical elements. I found that all existing systems were artificial and therefore unsuitable for my purpose; I sought to establish a natural one.” system. To this end, I wrote the symbols of the elements and their atomic weights on small pieces of cardboard, after which I began to group them different ways according to their similarity. But this method did not satisfy me until I arranged the cardboards one after the other according to the increase in atomic weight. When I placed the first row in the table:

H=1, Li=7, Be=9, B=11, C=12, N=14, O=16, F=19,

I have found that the following elements can form a second row under the first, but starting under the lithium. Next I found that in this new row:

Na=23, Mg=24, Al=27, Si=28, P=31, S=32, Cl=35.5

sodium repeats every property of lithium; the same thing happens for the following elements. The same repetition occurs in the third row, after a certain period, and continues in all rows."

This is the story told from his words. Further, in explanation and development of this story, it is said that he “arranged similar elements into groups and, according to the increase in atomic weights, into rows in which the properties and character of the elements changed gradually, as can be seen above. On the left side of his table there were “electropositive” elements, on right "electronegative". He proclaimed his law in the following words"

Thus, the story conveyed by him from his words concerns not the entire discovery as a whole and not the entire history of the creation of the natural system of elements, but only the final stage of this discovery, when, on the basis of an already created system, he was able to discover and formulate the periodic law of chemicals underlying this system elements. In short, the story conveyed by Brauner concerns not the history of the composition of a system of elements, but the history of the formulation of the periodic law on the basis of an already compiled system.

An indication of the existence of a fourth version is contained in the editorial afterword to the second volume of selected works, published in 1934. and containing works related to the periodic law. writes that in the indicated volume “only one article “Comment j” ai trouve la loi periodique” was not included as of a more biographical nature." For some reason he did not provide a link to where this article was published. This article, naturally, caused a huge interest, since, judging by its name, one could expect that it would finally give an answer to the question of interest to all chemists about how the periodic law was discovered, and this answer would be received not from third parties with words, but from himself. The reference to the fact that this article was excluded by Prof. as supposedly of a more biographical nature seemed completely unfounded. That is why it should have been included in the collection of works on the periodic law, and not excluded from this collection. As a result of searching for this article, it was discovered , that in the French journal of pure and applied chemistry for 1899, an article was actually published under the intriguing title “Comment j”ai trouve le systeme periodique des elements” (“How I found the periodic system of elements”). In a note to this article, the editors of the magazine report that they turned to D.I. Mendeleev on the occasion of his election in 1899. foreign corresponding member of the Paris Academy of Sciences with a request to write for the journal about his periodic system. fulfilled this request with great willingness and sent his work, written in Russian, to a French magazine. The translation of this work into French was carried out by the editors themselves.

The nearest familiarization with the text published on French the article shows that this is not some new work, but an exact translation from his article "Periodic Law of Chemical Elements", which he wrote for Encyclopedic Dictionary Brockhaus and Efron, and it was published in the XXIII volume of this dictionary in 1898. Obviously, the translator or the editors of the French magazine, in order to add more interest, changed the title that seemed too dry: “Periodic Law of Chemical Elements” to the intriguing: “How I Found the Periodic System of the Elements.” Otherwise, everything remained unchanged, and I did not add anything biographical to my article.

These are the legends and stories about how the periodic table of chemical elements was discovered. All the ambiguities generated by them can above be considered eliminated thanks to the discovery and study of new materials related to the history of this great discovery.

Fig.4. "Experience of a system of elements"

On March 6, 1869, at a meeting of the Russian Chemical Society, in the absence of Mendeleev (Mendeleev was at the cheese factories in the Tver region and, perhaps, stopped by his estate “Boblovo” in the Moscow region), a message about the discovery of the periodic law was made by him, who received it for the next issue of his journal (“Journal of the Russian Chemical Society”) article.

In 1871, in the final article “Periodic Law of Chemical Elements,” Mendeleev gave the following formulation of the Periodic Law: “The properties of the elements, and therefore the properties of the simple and complex bodies they form, are periodically dependent on the atomic weight.” At the same time, Mendeleev gave his periodic table a form that became classic (the so-called short version).

Unlike his predecessors, Mendeleev not only compiled a table and pointed out the presence of undoubted patterns in the numerical values of atomic weights, but also decided to name these patterns common law nature. Based on the assumption that atomic mass determines the properties of an element, he took it upon himself to change the accepted atomic weights of some elements and describe in detail the properties of still undiscovered elements.

Fig.5. Periodic Table of Chemical Elements

D.I. Mendeleev fought for the recognition of the Periodic Law for many years; his ideas received recognition only after the elements predicted by Mendeleev were discovered: gallium (Paul Lecoq de Boisbaudran, 1875), scandium (Lars Nilsson, 1879) and germanium (Clemens Winkler, 1886) - respectively eka-aluminum, eca-boron and eca-silicon. From the mid-1880s, the Periodic Law was finally recognized as one of the theoretical foundations chemistry.

Conclusion

The periodic law played a huge role in the development of other chemistry natural sciences. The mutual relationship between all elements and their physical and chemical properties was discovered. This presented natural science with a scientific and philosophical problem of enormous importance: this mutual connection must be explained. After the discovery of the Periodic Law, it became clear that the atoms of all elements must be built according to a single principle, and their structure must reflect the periodicity of the properties of the elements. Thus, the periodic law became an important link in the evolution of atomic-molecular science, having a significant impact on the development of the theory of atomic structure. He also contributed to the formulation modern concept"chemical element" and clarifying ideas about simple and complex substances. Advances in atomic physics, including nuclear energy and the synthesis of artificial elements, became possible only thanks to the Periodic Law.

“New theories and brilliant generalizations will appear and die. New ideas will replace our already outdated concepts of the atom and electron. The greatest discoveries and experiments will nullify the past and open today horizons of incredible novelty and breadth - all this will come and go, but Mendeleev’s Periodic Law will always live and guide the search.”

Bibliography

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