The opening of the periodic table briefly. Periodic system of Mendeleev. Chemical elements of the periodic system. New facts of brilliant foresight

The approval of the atomic-molecular theory at the turn of the 119th - 19th centuries was accompanied by a rapid growth 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 obtained 6 new simple substances (sodium, potassium, magnesium, calcium, barium, strontium) using electrolysis. 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 elements. Many scientists have been looking for patterns in the list of elements and have made some progress. There are three most significant works that challenged the priority of the discovery of the periodic law by D.I. Mendeleev.

Mendeleev formulated the periodic law in the form of the following main provisions:

• 1. Elements arranged by atomic weight represent a distinct periodicity of properties.
• 2. We must 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 value of the atomic weight of an element can sometimes be corrected by knowing its analogies.

Some analogies are revealed by the magnitude 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 yet undiscovered elements, 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 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 version of the periodic table of elements. The first draft of the table of elements appeared on February 17 (March 1, according to the new style), 1869.

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

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

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

And since the mass of a substance, although not absolute, but only relative, is finally expressed in the form of the weights of atoms, it is necessary to look for a functional correspondence between the individual properties of elements and their atomic weights. To look for something, even mushrooms or some kind of addiction, is impossible otherwise than by looking and trying.

So I began to select, writing on separate cards elements with their atomic weights and fundamental properties, similar elements and close atomic weights, which quickly led to the conclusion that the properties of elements are in a periodic dependence on their atomic weight, moreover, doubting many ambiguities, I did not doubt for a minute the generality of the conclusion drawn, since it is impossible to admit an accident.

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 noble gases. This can be seen from a page fragment from an article by D.I. Mendeleev, containing the periodic system of elements.

Based on the principle of increasing atomic weights, then 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 of 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 at once. In addition, he placed tellurium in front of iodine, although the latter has a lower atomic weight. With such an arrangement of elements, all horizontal rows in the table contained only similar elements, and the periodicity of changes in the properties of elements was clearly manifested. 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, in which the periodic system is given in an almost modern form.

8 groups of elements were formed in the table, the group numbers indicate the highest valency 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, described with amazing accuracy the properties of three unknown elements, which he called ekabor (eka on Sanskrit means "one and the same"), ekaaluminum and ekasilicon. (Gallia 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 coincide with the properties of ekaaluminum predicted by him, and informed Lecoq de Boisbaudran that he had 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 accurate measurements led to the correct value of 5.904 g/cm3. The final recognition of the periodic law of D.I. Mendeleev achieved after 1886, when the German chemist K. Winkler, analyzing silver ore, received an element that he called germanium. It turns out to be an exacilium.

Periodic law and the periodic system of elements.

The periodic law is one of the most important laws of chemistry. Mendeleev believed that the main characteristic of an element is its atomic mass. Therefore, he arranged all the elements in one row in order of increasing their 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 valency of the elements increases from I y Li to V y N (oxygen and fluorine have constant valence II and I, respectively) and from I y Na to VII y Cl. The next element K, like Li and Na, has valence I. In the series of oxides from Li2O to N2O5 and hydroxides from LiOH to HNO3, the basic properties are weakened, and the acidic properties are enhanced. The properties of oxides change similarly in the series from Na2O and NaOH to Cl2O7 and HClO4. Potassium oxide K2O, like 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 shapes and properties of nonmetals change similarly from CH4 to HF and from SiH4 to HCl.

This nature 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 magnitude of the atomic mass.

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

· The properties of the elements, as well as the forms and properties of the compounds of the elements are in a periodic dependence on the value of the atomic mass of the elements.

Mendeleev arranged the periods of the elements under each other and as a result compiled the periodic table of 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.

To create a modern table, it took many years of hard work of thousands and thousands of chemists and physicists. If Mendeleev were alive now, looking at the modern table of elements, he could well repeat the words of the English chemist J. W. Mellor, the 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 rank and file 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 graphical 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 are only in trace amounts). The rest23 were obtained artificially as a result of nuclear reactions - this is the process of transformation of atomic nuclei, which occurs when they interact with elementary particles, gamma quanta and with each other, usually leading to the release of an enormous amount of energy. The first 112 elements have permanent names, the rest are temporary.

The discovery of the 112th element (the heaviest of the official ones) is recognized by the International Union of Theoretical 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 ununbium; it was first synthesized in February 1996 at the heavy ion accelerator at the Heavy Ion Institute in Darmstadt. The discoverers have half a year to propose a new official name to add to the table (they have already proposed Wickshausius, Helmholtius, Venusius, Frisch, Strassmanius and Heisenberg). At present, transuranium elements with numbers 113-116 and 118, obtained at the Joint Institute for Nuclear Research in Dubna, are known, 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 "extra-long" version, each period occupies exactly one line. In the "long" version, 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 in their chemical properties) are taken out of the general table making it more compact. In the "short" form of entry, in addition to this, the fourth and subsequent periods occupy 2 lines; 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 abolished by IUPAC in 1989. Despite the recommendation to use the long form, the short form continued to appear in large numbers Russian reference books and manuals and after that time. From modern foreign literature, the short form is completely excluded; instead, the long form is used. Some researchers associate this situation, among other things, with the seemingly rational compactness of the short form of the table, as well as with stereotyped thinking and a lack of perception of modern (international) information.

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

There are many other, rarely or not used at all, but very original, ways of graphic display Periodic Law. Today, there are several hundred versions of the table, while scientists offer more and more new options.

Periodic law and its justification.

The periodic law made it possible to bring into the system and generalize a huge amount of scientific information in chemistry. This function of the law is called integrative. It manifests itself especially clearly in the structuring of scientific and educational material chemistry.

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

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

This happened with the characteristics of beryllium. Prior to 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 element. It was at this stage that Mendeleev suspected a mistake in researching the properties of beryllium, he found the work of the Russian chemist Avdeev, who claimed that beryllium is divalent and has an atomic weight of 9. Avdeev’s work remained unnoticed academia, 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).

Ten more elements had only atomic weights corrected. And all these refinements 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 on an intuitive level, but with the formation of the system, Mendeleev was able to calculate their properties with a high degree of accuracy. Good 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 discovered by himself.

In total, twelve elements were predicted by Mendeleev. 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. It suffices to give an example to confirm this. Since 1929, when Academician P. L. Kapitsa first discovered the non-metallic conductivity of germanium, the development of the theory 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 compounds of elements located in periods equally distant from this group (for example, with a general formula of the AzB type) should have semiconductor properties to a greater or lesser extent.

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

It is important to note that predictions within the framework of the Periodic System were made even after its universal recognition. In 1913

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

Only later were serial numbers associated with the value of the positive charge of the nucleus. On the other hand, Moseley's law made it possible to immediately experimentally confirm the number of elements in periods and, at the same time, to 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 dispute: to separate inert gases into an independent zero group of elements or to consider them 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 inert gases, directly pointing to the possible stability of their fluorides and oxides.

But only in 1962, the American chemist Neil Bartlett for the first time carried out the reaction of platinum hexafluoride with oxygen under the most ordinary conditions, obtaining xenon hexafluoroplatinate XePtF ^, and after it other gas compounds, which are now more correctly called noble, and not inert.

Here the reader will find information about one of the most important laws ever discovered by man in the scientific field - the periodic law of Mendeleev Dmitry Ivanovich. You will get acquainted with its meaning and influence on chemistry, the general provisions, characteristics and details of the periodic law, the history of discovery and the main provisions will be considered.

What is the periodic law

The periodic law is a natural law of a fundamental nature, which was first discovered by D. I. Mendeleev back in 1869, and the discovery itself was due to a comparison of the properties of some chemical elements and the atomic mass values ​​known at that time.

Mendeleev argued that, according to his law, simple and complex bodies and various compounds of elements depend on their dependence of the periodic type and on the weight of their atom.

The periodic law is unique in its kind and this is due to the fact that it is not expressed by mathematical equations, unlike other fundamental laws of nature and the universe. Graphically, it finds its expression in the periodic table of chemical elements.

Discovery history

The discovery of the periodic law took place in 1869, but attempts to systematize all known x elements began long before that.

The first attempt to create such a system was made by I. V. Debereiner in 1829. He classified all the chemical elements known to him into triads, interconnected by the proximity of half the sum of the atomic masses included in this group of three components. Following Debereiner, an attempt was made to create a unique table of classification of the elements by A. de Chancourtua, he called his system the "earth spiral", and after him the Newlands octave was compiled by John Newlands. In 1864, almost simultaneously, William Olding and Lothar Meyer published independently created tables.

The periodic law was presented to the scientific community for review on March 8, 1869, and this happened during a meeting of the Russian X-th society. Mendeleev Dmitry Ivanovich announced his discovery in front of everyone and in the same year Mendeleev's textbook "Fundamentals of Chemistry" was published, where the periodic table created by him was shown for the first time. A year later, in 1870, he wrote an article and submitted it for review to the RCS, where the concept of the periodic law was first used. In 1871, Mendeleev gave an exhaustive description of his research in his famous article on the periodic validity of chemical elements.

An invaluable contribution to the development of chemistry

The value of the periodic law is incredibly great for the scientific community around the world. This is due to the fact that its discovery gave a powerful impetus to the development of both chemistry and other natural sciences, such as physics and biology. The relationship of the elements with their qualitative chemical and physical characteristics was open, and this also made it possible to understand the essence of building all the elements according to one principle and gave rise to the modern formulation of the concepts of chemical elements, to concretize the knowledge of the idea of ​​​​substances of complex and simple structure.

The use of the periodic law made it possible to solve the problem of chemical prediction, to determine the cause of the behavior of known chemical elements. Atomic physics, including nuclear energy, became possible as a result of the same law. In turn, these sciences made it possible to expand the horizons of the essence of this law and delve into its understanding.

Chemical properties of the elements of the periodic system

In fact, the chemical elements are interconnected by the characteristics inherent in them in the state of both a free atom and an ion, solvated or hydrated, in a simple substance and in the form that their numerous compounds can form. However, x-th properties usually consist in two phenomena: properties characteristic of an atom in a free state, and a simple substance. This kind of properties includes many of their types, but the most important are:

1. Atomic ionization and its energy, depending on the position of the element in the table, its ordinal number.
2. The energy relationship of the atom and electron, which, like atomic ionization, depends on the location of the element in the periodic table.
3. The electronegativity of an atom, which does not have a constant value, but can change depending on various factors.
4. The radii of atoms and ions - here, as a rule, empirical data are used, which is associated with the wave nature of electrons in a state of motion.
5. Atomization of simple substances - a description of the ability of an element to reactivity.
6. The oxidation states are a formal characteristic, however, appearing as one of the most important characteristics of an element.
7. The oxidation potential for simple substances is a measurement and indication of the potential of a substance to act in aqueous solutions, as well as the level of manifestation of redox properties.

Periodicity of elements of internal and secondary type

The periodic law gives an understanding of another important component of nature - internal and secondary periodicity. The aforementioned fields of study of atomic properties are, in fact, much more complex than one might think. This is due to the fact that the elements s, p, d of the table change their qualitative characteristics depending on their position in the period (internal periodicity) and group (secondary periodicity). For example, the internal process of the transition of the element s from the first group to the eighth to the p-element is accompanied by minimum and maximum points on the energy curve of the ionized atom. This phenomenon shows the internal inconstancy of the periodicity of changes in the properties of an atom according to its position in the period.

Results

Now the reader has a clear understanding and definition of what Mendeleev's periodic law is, realizes its significance for man and the development of various sciences, and has an idea of ​​​​its current provisions and the history of discovery.

abstract

“The history of the discovery and confirmation of the periodic law by D.I. Mendeleev"

St. Petersburg 2007

Introduction

Periodic law D.I. Mendeleev is a fundamental law that establishes a periodic change in the properties of chemical elements depending on the increase in the charges of the nuclei of their atoms. Discovered by D.I. Mendeleev in February 1869. When comparing the properties of all the elements known at that time and the values ​​of their atomic masses (weights). The term "periodic law" was first used by Mendeleev in November 1870, and in October 1871 he gave the final formulation of the Periodic Law: "... the properties of the elements, and therefore the properties of the simple and complex bodies they form, are in periodic dependence on their atomic weight." The graphical (tabular) expression of the periodic law is the periodic system of elements developed by Mendeleev.

1. Attempts by other scientists to derive the periodic law

The periodic system, or periodic classification, of the elements was of great importance for the development of inorganic chemistry in the second half of the 19th century. This value is currently colossal, because the system itself, as a result of studying the problems of the structure of matter, gradually acquired that degree of rationality that could not be achieved by knowing only atomic weights. The transition from empirical regularity to law is the ultimate goal of any scientific theory.

The search for the basis of the natural classification of chemical elements and their systematization began long before the discovery of the Periodic Law. The difficulties faced by the natural scientists who were the first to work in this area were caused by the lack of experimental data: at the beginning of the 19th century. the number of known chemical elements was still too small, and the accepted values ​​of the atomic masses of many elements were inaccurate.

Apart from the attempts of Lavoisier and his school to give a classification of elements on the basis of the criterion of analogy in chemical behavior, the first attempt at a periodic classification of elements belongs to Döbereiner.

Döbereiner triads and the first systems of elements

In 1829, the German chemist I. Döbereiner attempted to systematize the elements. He noticed that some elements similar in their properties can be combined into groups of three, which he called triads: Li–Na–K; Ca-Sr-Ba; S-Se-Te; P–As–Sb; Cl–Br–I.

The essence of the proposed the law of triads Döbereiner 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. Although Döbereiner naturally failed to break 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.

Döbereiner's ideas were developed by L. Gmelin, who showed that the relationship between the properties of elements and their atomic masses is much more complicated than triads. In 1843, Gmelin published a table in which chemically similar elements were arranged into groups in ascending order of their connecting (equivalent) weights. The elements formed triads, as well as tetrads and pentads (groups of four and five elements), and the electronegativity of the elements in the table changed smoothly from top to bottom.

In the 1850s M. von Pettenkofer and J. Dumas proposed the so-called. differential systems aimed at identifying general patterns in the change in the atomic weight of elements, which were developed in detail by German chemists A. Strekker and G. Chermak.

In the early 60s of the XIX century. several works appeared at once that immediately preceded the Periodic Law.

Spiral de Chancourtois

A. de Chancourtua 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 the surface of the cylinder was unfolded, it turned out that on vertical lines parallel to the axis of the cylinder, 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 elements of a completely different chemical behavior appeared on the same line with elements that were similar in their chemical nature. Manganese fell into the group of alkali metals, and titanium, which had nothing to do with them, fell into the group of oxygen and sulfur.

Newlands table

The English scientist J. Newlands in 1864 published a table of elements reflecting the proposed by him law of octaves. Newlands showed that in a series of elements arranged in ascending order of atomic weights, the properties of the eighth element are similar to those of the first. Newlands tried to give this dependence, which actually takes place for light elements, a universal character. In his table, similar elements were arranged in horizontal rows, but elements of completely different properties often turned out to be in the same row. In addition, Newlands was forced to place two elements in some cells; finally, the table did not contain empty seats; as a result, the law of octaves was accepted extremely skeptically.

Odling and Meyer tables

In the same 1864, the first table of the German chemist L. Meyer appeared; 28 elements were included in it, placed 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.

In 1870, Meyer published a new table called "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. What was done before the day of the great discovery

The prerequisites for the discovery of the periodic law should be sought in the book of D.I. Mendeleev (hereinafter D.I.) "Fundamentals of Chemistry". The first chapters of the 2nd part of this book by D.I. wrote at the beginning of 1869. The 1st chapter was devoted to sodium, the 2nd - to its analogues, the 3rd - to heat capacity, the 4th - to alkaline earth metals. By the day of the discovery of the periodic law (February 17, 1869), he probably already managed to set out the question of the ratio of such polar-opposite elements as alkali metals and halides, which were close to each other in terms of their atomicity (valency), as well as the question about the ratio of the alkali metals themselves in terms of their atomic weights. He came close to the issue of bringing together and comparing two groups of polar opposite elements in terms of the atomic weights of their members, which in fact already meant the rejection of the principle of distributing elements according to their atomicity and the transition to the principle of their distribution according to atomic weights. This transition was not a preparation for the discovery of the periodic law, but already the beginning of the discovery itself.

By the beginning of 1869, a significant part of the elements were combined into separate natural groups and families on the basis of common chemical properties; along with this, the other part of them was scattered, standing apart separate elements that were not united in special groups. The following were considered firmly established:

- a group of alkali metals - lithium, sodium, potassium, rubidium and cesium;

- a group of alkaline earth metals - calcium, strontium and barium;

– oxygen group – oxygen, sulfur, selenium and tellurium;

- nitrogen group - nitrogen, phosphorus, arsenic and antimony. In addition, bismuth was often added here, and vanadium was considered as an incomplete analogue of nitrogen and arsenic;

- carbon group - carbon, silicon and tin, and titanium and zirconium were considered as incomplete analogs of silicon and tin;

- a group of halogens (halides) - fluorine, chlorine, bromine and iodine;

– copper group – copper and silver;

– zinc group – zinc and cadmium

– iron family – iron, cobalt, nickel, manganese and chromium;

- family of platinum metals - platinum, osmium, iridium, palladium, ruthenium and rhodium.

The situation was more complicated with such elements that could be assigned to different groups or families:

- lead, mercury, magnesium, gold, boron, hydrogen, aluminum, thallium, molybdenum, tungsten.

In addition, a number of elements were known, the properties of which were not yet sufficiently studied:

- a family of rare earth elements - yttrium, "erbium", cerium, lanthanum and "didim";

– niobium and tantalum;

– beryllium;

3. Grand opening day

DI. was a very versatile scientist. For a long time he was very interested in questions Agriculture. He took the closest part in the activities of the Free Economic Society in St. Petersburg (VEO), of which he was a member. VEO organized artel cheese-making in a number of northern provinces. One of the initiators of this initiative was N.V. Vereshchagin. At the end of 1868, i.e. while D.I. finished issue. 2 of his book, Vereshchagin turned to the VEO with a request to send one of the members of the Society in order to inspect the work of the artel cheese factories on the spot. Consent to this kind of trip was expressed by D.I. In December 1868, he examined a number of artel cheese factories in the Tver province. An additional business trip was needed to complete the survey. Just on February 17, 1869, the departure was scheduled.

In his 1668 work, Robert Boyle provided a list of indecomposable chemical elements. There were only fifteen of them at that time. At the same time, the scientist did not claim that, in addition to the elements he listed, there were no more, and the question of their number remained open.

A hundred years later, the French chemist Antoine Lavoisier compiled a new list of elements known to science. 35 were included in his roster chemical substances, of which 23 were subsequently recognized as those same indecomposable elements.

The search for new elements was carried out by chemists all over the world and progressed quite successfully. The decisive role in this issue was played by the Russian chemist Dmitry Ivanovich Mendeleev: it was he who came up with the idea of ​​the possibility of a relationship between the atomic mass of elements and their place in the "hierarchy". In his own words, "it is necessary to look for ... correspondences between the individual properties of elements and their atomic weights."

Comparing the chemical elements known at that time, Mendeleev, after a colossal work, eventually discovered that dependence, the general regular connection between the individual elements, in which they appear as a single whole, where the properties of each element are not something that exists by itself, but periodically and a regularly recurring phenomenon.

So in February 1869 it was formulated periodic law of Mendeleev. In the same year, on March 6, a report prepared by D.I. Mendeleev, under the title "Relationship of properties with the atomic weight of elements" was presented by N.A. Menshutkin at a meeting of the Russian Chemical Society.

In the same year, the publication appeared in the German magazine "Zeitschrift für Chemie", and in 1871, a detailed publication by D.I. Mendeleev, dedicated to his discovery - "Die periodische Gesetzmässigkeit der Elemente" (Periodic regularity of chemical elements).

Creating a Periodic Table

Despite the fact that the idea was formed by Mendeleev in a rather short period of time, he could not formalize his conclusions for a long time. It was important for him to present his idea in the form of a clear generalization, a strict and visual system. As D.I. Mendeleev in a conversation with Professor A.A. Inostrantsev: "Everything came together in my head, but I can't express it in a table."

According to biographers, after this conversation, the scientist worked on creating the table for three days and three nights, not going to bed. He went through various options in which elements could be combined to organize in a table. The work was also complicated by the fact that at the time of the creation of the periodic system, not all chemical elements were known to science.

In 1869-1871, Mendeleev continued to develop the ideas of periodicity put forward and accepted by the scientific community. One of the steps was the introduction of the concept of the place of an element in the periodic system as a set of its properties in comparison with the properties of other elements.

It was on the basis of this, and also based on the results obtained in the course of studying the sequence of changes in glass-forming oxides, that Mendeleev corrected the values ​​of the atomic masses of 9 elements, including beryllium, indium, uranium and others.

During the work of D.I. Mendeleev sought to fill in the empty cells of his table. As a result, in 1870 he predicted the discovery of elements unknown at that time to science. Mendeleev calculated atomic masses and described the properties of three elements not yet discovered at that time:

• "ekaaluminum" - discovered in 1875, named gallium,
• "ekabora" - discovered in 1879, named scandium,
• "ekasilicia" - discovered in 1885, named germanium.

His next realized predictions were the discovery of eight more elements, including polonium (discovered in 1898), astatine (discovered in 1942-1943), technetium (discovered in 1937), rhenium (discovered in 1925) and France (discovered in 1939).

In 1900, Dmitry Ivanovich Mendeleev and William Ramsay came to the conclusion that it was necessary to include elements of a special, zero group in the periodic system. Today, these elements are called noble gases (until 1962, these gases were called inert gases).

The principle of organization of the periodic system

In his table, D.I. Mendeleev arranged the chemical elements in rows in order of increasing mass, choosing the length of the rows so that the chemical elements in the same column had similar chemical properties.

Noble gases - helium, neon, argon, krypton, xenon and radon are reluctant to react with other elements and show low chemical activity and therefore are in the far right column.

In contrast, the elements of the leftmost column - lithium, sodium, potassium and others react violently with other substances, the process is explosive. Elements in other columns of the table behave similarly - inside the column, these properties are similar, but vary when moving from one column to another.

The periodic system in its first version simply reflected the state of affairs existing in nature. Initially, the table did not explain in any way why this should be so. And only with the advent of quantum mechanics did the true meaning of the arrangement of elements in the periodic table become clear.

Chemical elements up to uranium (contains 92 protons and 92 electrons) are found in nature. Starting with number 93, there are artificial elements created in the laboratory.

Ministry of Education and Science of the Russian Federation

Department of Education of the Administration of Tver

Municipal educational institution

"Evening (shift) general education school No. 2", Tver

Competition of student essays "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 MOU VSOSH No. 2, Tver

Supervisor:

chemistry teacher of the highest category

MOU VSOSH No. 2, Tver

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

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

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

1.2. Döbereiner 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. In honor of Russia approved gold medal It is awarded for outstanding work in chemistry. The name of the scientist was given to the Russian Chemical Society. In honor of the annual Regional Mendeleev readings are held in the Tver region. Even the element with serial number 101 was given the name mendelevium, in honor of Dmitry Ivanovich.

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

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

1. Prerequisites for the discovery of the Periodic Law

The search for the basis of 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, the composition and properties of their compounds were described.

1.1 Classification

An outstanding Swedish chemist divided all elements into metals and non-metals based on differences in the properties of the simple substances and compounds formed by them. He determined that metals correspond to basic oxides and bases, and non-metals to acid 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 similar in their properties could be combined in groups of three, which he called triads.

The essence of the proposed Döbereiner triad law 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 Debereiner's triads are to some extent the prototypes of Mendeleev's groups, these representations 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 an artificial limitation of sets of similar elements to only triple unions. Very revealing in this sense is Debereiner's failure to single out 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 limited himself in advance to the search for triads, he could not find the right solution. Half a century later, Lothar Mayer will say that if Döbereiner had even briefly digressed from his triads, he would immediately see the similarity of all these four elements at the same time.

Although Döbereiner naturally failed to break 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)

The professor of the Paris Higher School, Alexandre Begier 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 the surface of the cylinder was unfolded, it turned out that on vertical lines parallel to the axis of the cylinder, 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, in this case, elements of a completely different chemical behavior turned out to be on the same line with elements that were similar in their chemical nature. Manganese fell into the group of alkali metals, and titanium, which had nothing to do 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 they did not pay attention to it, and soon it was forgotten.

Shortly after the de Chancourtois spiral, the American scientist John Newlands made an attempt to correlate the chemical properties of elements with their atomic masses. Arranging the elements in ascending order of their atomic masses, Newlands noticed that there was a similarity in properties 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 in vertical groups of seven elements each, and at the same time found that (with a slight change in the order of some elements) elements similar in chemical properties appear on the same horizontal line. John Newlands, by far, was the first to give a series of elements arranged in ascending order of atomic masses, assigned the corresponding serial number to the chemical elements, and noticed a 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 (masses) 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 takes place for light elements, a universal character. In his table, similar elements were arranged in horizontal rows, but elements of completely different properties often turned out to be in the same row. The London Chemical Society met 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

In the same 1864, the first table of the German chemist Lothar Meyer appeared; 28 elements were included in it, placed 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 published a new table called 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 element's atomic volume versus atomic weight, which has a characteristic sawtooth shape that perfectly illustrates 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 legend, which has not yet been verified due to the lack of relevant documentary data. The story of the professor of geology of St. Petersburg is interesting. University (), close friend . , who visited just in those days when he discovered the periodic law, gives curious strokes of how he worked on the creation of his system of elements, who published the story, wrote:

“About the final creative process of Mendeleev’s intuition, Honored Professor Alexander Alexandrovich Inostrantsev Kindly told me extremely interesting things. Once, already being the secretary of the Faculty of Physics and Mathematics, A. A. went to visit Mendeleev, with whom, as a scientist and close friend, he was in constant spiritual communication. He sees: D. I. is standing at the desk, apparently in a gloomy, depressed state.

What are you doing, Dmitry Ivanovich?

Mendeleev spoke about what was later embodied in the periodic table of elements, but at that moment the law and the table had not yet been formed: “Everything has developed in my head,” Mendeleev added bitterly, “but I can’t express it in a table.” A little later, the following happened. Mendeleev spent three days and three nights, not going to bed, and worked at the desk, 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. “I see in a dream a table where the elements are arranged as needed. I woke up, immediately wrote it down on a piece of paper - only in one place did it later turn out to be the necessary amendment.

Further, it is necessary to take into account the testimony of himself in the "Fundamentals of Chemistry" about how, in the final formulation of his classification of elements, he used cards on which data on individual elements were written. The cards were needed precisely to identify the still unknown relationship between the 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 located not in the order of groups and rows (periods), but only in the order of groups (the periods were not yet open at first). The groups were placed one under the other, and it was precisely the placement of the groups that led to the discovery that the vertical columns (periods) of the elements adjoin each other, forming a common continuous row of elements in which certain chemical properties are periodically repeated. This, in fact, was the discovery of the periodic law.

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

The third story, transmitted again from the words of himself, 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 by Czechoslovak chemists. During World War II, Gerald Druce featured this story in his biography of Bohuslav Brauner. According to Brauner, he told him about how the compilation of a textbook on chemistry, that is, "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 chemical elements. I found that all existing systems are artificial, and therefore unsuitable for my purpose; I sought to establish a natural systems To this end, I wrote on small pieces of cardboard the signs of the elements and their atomic weights, after which I began to group them different ways according to their similarity. But this method did not satisfy me until I arranged the cartons 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 below the first, but start below 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 happens with the following elements. The same repetition occurs in the third row, after a certain period, and continues in all rows.

Such is the story, transmitted from his words. Further, in the 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 nature of the element changed gradually, as can be seen above. On the left side of his table were "electropositive" elements, on right "electronegative". He proclaimed his law in the following words"

Thus, the story, transmitted by him from words, does not concern 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 chemical substances underlying this system. elements. In short, the story given by Brauner does not concern the history of the compilation of the 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 placed as a more biographical one. For some reason, he did not give links 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 from words, but from himself. The reference to the fact that this article was excluded by Prof. as supposedly more biographical in 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. 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 mu elements"). In a footnote to this article, the editors of the journal 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 a journal about his periodic system. fulfilled this request with great pleasure 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 closest acquaintance with the text published on French article shows that this is not some new work, but an exact translation from his article "Periodic Law of the 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 give more interest, changed the seemingly too dry title: "Periodic Law of the Chemical Elements" to the intriguing: "How I Found the Periodic Table of the Elements." Otherwise, everything remained unchanged, and he did not add anything biographical to his 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 the system of elements"

On March 6, 1869, at a meeting of the Russian Chemical Society, in the absence of Mendeleev (Mendeleev was at cheese dairies in the Tver region and, possibly, stopped by his estate "Boblovo" in the Moscow region), a message about the discovery of the periodic law was made, having received for the next issue of his journal ("Journal of the Russian Chemical Society") article.

In 1871, in the final article "The 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 formed by them, are in a periodic dependence on the atomic weight." At the same time, Mendeleev gave his periodic table a form that became classical (the so-called short version).

Unlike his predecessors, Mendeleev not only compiled a table and pointed out the presence of undoubted regularities in the numerical values ​​of atomic weights, but also decided to call these regularities a general law of nature. Based on the assumption that atomic mass determines the properties of an element, he took the liberty of changing the accepted atomic weights of some elements and describing in detail the properties of elements that have not yet been discovered.

Fig.5. Periodic system of chemical elements

D. I. Mendeleev for many years fought for the recognition of the Periodic Law; his ideas were recognized only after the elements predicted by Mendeleev were discovered: gallium (Paul Lecoq de Boisbaudran, 1875), scandium (Lars Nilsson, 1879) and germanium (Clemens Winkler, 1886) - ekaaluminum, ecabor and ekasilicon, respectively. Since the mid-1880s, the Periodic Law has been finally recognized as one of the theoretical foundations chemistry.

Conclusion

The periodic law played a huge role in the development of the chemistry of other natural sciences. The mutual relationship between all elements, their physical and chemical properties was discovered. This posed before natural science a scientific and philosophical problem of great 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 and molecular science, having a significant impact on the development of the theory of the structure of the atom. He also contributed to the formulation modern concept"chemical element" and clarifying ideas about simple and complex substances. The successes of atomic physics, including nuclear energy and the synthesis of artificial elements, became possible only thanks to the Periodic Law.

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

Bibliography

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3. . Selected lectures in chemistry. - M .: Higher. school, 1968. - 224 p.

four. . New materials on the history of the discovery of the periodic law. - M.-L.: Publishing House of Acad. Sciences of the USSR, 1950. - 145 p.

5. . Philosophical analysis of the first works on the periodic law (). - M.: Publishing House of Acad. Sciences of the USSR, 1959. - 294 p.

6. . Philosophy of invention and invention in philosophy. - T.2. - M.: Science and School, 1922.- P.88.