Introduction

The periodic law and the Periodic Table of Chemical Elements by D.I. Mendeleev are the basis of modern chemistry. They refer to such scientific patterns that reflect phenomena that actually exist in nature, and therefore will never lose their significance.

The periodic law and the discoveries made on its basis in various fields of natural science and technology are the greatest triumph of the human mind, evidence of ever deeper penetration into the most intimate secrets of nature, the successful transformation of nature for the benefit of man.

“It rarely happens that a scientific discovery turns out to be something completely unexpected, it is almost always anticipated, but subsequent generations, who use proven answers to all questions, often find it difficult to appreciate what difficulties it cost their predecessors.” DI. Mendeleev.

Purpose: To characterize the concept of a periodic system and the periodic law of elements, the periodic law and its rationale, to characterize the structures of the periodic system: subgroups, periods and groups. Study the history of the discovery of the periodic law and the periodic system of elements.

Objectives: Consider the history of the discovery of the periodic law and the periodic system. Define the periodic law and the periodic system. Analyze the periodic law and its rationale. The structure of the periodic table: subgroups, periods and groups.

The history of the discovery of the periodic law and the periodic system of chemical elements

The establishment of the atomic-molecular theory at the turn of the 18th and 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. We can highlight three of the most significant works that challenged the priority of the discovery of the periodic law by D.I. Mendeleev.

In 1860, the first International Chemical Congress took place, after which it became clear that the main characteristic of a chemical element is its atomic weight. The French scientist B. De Chancourtois in 1862 was the first to arrange the elements in order of increasing atomic weights and arrange them in a spiral around a cylinder. Each turn of the spiral contained 16 elements, similar elements, as a rule, fell into vertical columns, although significant differences were also noted. De Chancourtois's work went unnoticed, but his idea of ​​sorting elements in order of increasing atomic weights proved fruitful.

And two years later, guided by this idea, the English chemist John Newlands arranged the elements in a table and noticed that the properties of the elements were repeated periodically every seven numbers. For example, chlorine is similar in properties to fluorine, potassium is similar to sodium, selenium is similar to sulfur, etc. Newlands called this pattern the “law of octaves,” almost anticipating the concept of a period. But Newlands insisted that the length of the period (equal to seven) is constant, so his table contains not only the correct patterns, but also random pairs (cobalt - chlorine, iron - sulfur and carbon - mercury).

But the German scientist Lothar Meyer in 1870 plotted the dependence of the atomic volume of elements on their atomic weight and discovered a clear periodic dependence, and the length of the period did not coincide with the law of octaves and was a variable value.

All these works have much in common. De Chancourtois, Newlands and Meyer discovered the manifestation of periodic changes in the properties of elements depending on their atomic weight. But they were unable to create a unified periodic system of all elements, since many elements did not find their place in the patterns they discovered. These scientists also failed to draw any serious conclusions from their observations, although they felt that the numerous relationships between the atomic weights of elements were a manifestation of some general law.

This general law was discovered by the great Russian chemist Dmitri Ivanovich Mendeleev in 1869. 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 valence). 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 there must be a connection between mass and chemical properties. 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.

If we proceed from the principle of increasing atomic weights, then the next elements after calcium should have been vanadium (A = 51), chromium (A = 52) and titanium (A = 52). 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 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 nonmetal, 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 ekaboron (eka in Sanskrit means “the same thing”), ekaaluminum and ekasilicon . Their modern names are Se, Ga, Ge.

The scientific world of the West was initially skeptical about the Mendeleev system and its predictions, but everything changed when in 1875 the French chemist P. Lecoq de Boisbaudran, examining the spectra of zinc ore, discovered traces of a new element, which he named gallium in honor of his homeland (Gallium - 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.

In 1879, the Swedish chemist L. Nilsson, while separating rare earth elements obtained from the mineral gadolinite, isolated a new element and named it scandium. This turns out to be the ecaboron predicted by Mendeleev.

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.


Related information.


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 of 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.

The discovery of the table of periodic chemical elements was one of the important milestones in the history of the development of chemistry as a science. The discoverer of the table was the Russian scientist Dmitry Mendeleev. An extraordinary scientist with a broad scientific outlook managed to combine all ideas about the nature of chemical elements into a single coherent concept.

M24.RU will tell you about the history of the discovery of the table of periodic elements, interesting facts related to the discovery of new elements and folk tales that surrounded Mendeleev and the table of chemical elements he created.

Table opening history

By the middle of the 19th century, 63 chemical elements had been discovered, and scientists around the world have repeatedly made attempts to combine all existing elements into a single concept. It was proposed to place the elements in order of increasing atomic mass and divide them into groups according to similar chemical properties.

In 1863, the chemist and musician John Alexander Newland proposed his theory, who proposed a layout of chemical elements similar to that discovered by Mendeleev, but the scientist’s work was not taken seriously by the scientific community due to the fact that the author was carried away by the search for harmony and the connection of music with chemistry.

In 1869, Mendeleev published his diagram of the periodic table in the Journal of the Russian Chemical Society and sent notice of the discovery to the world's leading scientists. Subsequently, the chemist repeatedly refined and improved the scheme until it acquired its usual appearance.

The essence of Mendeleev's discovery is that with increasing atomic mass, the chemical properties of elements change not monotonically, but periodically. After a certain number of elements with different properties, the properties begin to repeat. Thus, potassium is similar to sodium, fluorine is similar to chlorine, and gold is similar to silver and copper.

In 1871, Mendeleev finally combined the ideas into the periodic law. Scientists predicted the discovery of several new chemical elements and described their chemical properties. Subsequently, the chemist’s calculations were completely confirmed - gallium, scandium and germanium fully corresponded to the properties that Mendeleev attributed to them.

Tales about Mendeleev

There were many tales about the famous scientist and his discoveries. People at that time had little understanding of chemistry and believed that studying chemistry was something like eating soup from babies and stealing on an industrial scale. Therefore, Mendeleev’s activities quickly acquired a mass of rumors and legends.

One legend says that Mendeleev discovered the table of chemical elements in a dream. This is not the only case; August Kekule, who dreamed of the formula of the benzene ring, also spoke about his discovery. However, Mendeleev only laughed at the critics. “I’ve been thinking about it for maybe twenty years, and you say: I was sitting there and suddenly... done!” the scientist once said about his discovery.

Another story credits Mendeleev with the discovery of vodka. In 1865, the great scientist defended his dissertation on the topic “Discourse on the combination of alcohol with water,” and this immediately gave rise to a new legend. The chemist’s contemporaries chuckled, saying that the scientist “creates quite well under the influence of alcohol combined with water,” and subsequent generations already called Mendeleev the discoverer of vodka.

They also laughed at the scientist’s lifestyle, and especially at the fact that Mendeleev equipped his laboratory in the hollow of a huge oak tree.

Contemporaries also made fun of Mendeleev’s passion for suitcases. The scientist, during his involuntary inactivity in Simferopol, was forced to while away the time by weaving suitcases. Later, he independently made cardboard containers for the needs of the laboratory. Despite the clearly “amateur” nature of this hobby, Mendeleev was often called a “master of suitcases.”

Discovery of radium

One of the most tragic and at the same time famous pages in the history of chemistry and the appearance of new elements in the periodic table is associated with the discovery of radium. The new chemical element was discovered by the spouses Marie and Pierre Curie, who discovered that the waste remaining after the separation of uranium from uranium ore was more radioactive than pure uranium.

Since no one knew what radioactivity was at that time, rumor quickly attributed healing properties and the ability to cure almost all diseases known to science to the new element. Radium was included in food products, toothpaste, and face creams. The rich wore watches whose dials were painted with paint containing radium. The radioactive element was recommended as a means to improve potency and relieve stress.

Such “production” continued for twenty years - until the 30s of the twentieth century, when scientists discovered the true properties of radioactivity and found out how destructive the effect of radiation is on the human body.

Marie Curie died in 1934 from radiation sickness caused by long-term exposure to radium.

Nebulium and Coronium

The periodic table not only ordered the chemical elements into a single harmonious system, but also made it possible to predict many discoveries of new elements. At the same time, some chemical "elements" were recognized as non-existent on the basis that they did not fit into the concept of the periodic law. The most famous story is the “discovery” of the new elements nebulium and coronium.

While studying the solar atmosphere, astronomers discovered spectral lines that they were unable to identify with any of the chemical elements known on earth. Scientists suggested that these lines belong to a new element, which was called coronium (because the lines were discovered during the study of the “corona” of the Sun - the outer layer of the star’s atmosphere).

A few years later, astronomers made another discovery while studying the spectra of gaseous nebulae. The discovered lines, which again could not be identified with anything terrestrial, were attributed to another chemical element - nebulium.

The discoveries were criticized because there was no longer room in Mendeleev's periodic table for elements with the properties of nebulium and coronium. After checking, it was discovered that nebulium is ordinary terrestrial oxygen, and coronium is highly ionized iron.

The material was created based on information from open sources. Prepared by Vasily Makagonov @vmakagonov

The periodic law of Dmitry Ivanovich Mendeleev is one of the fundamental laws of nature, which links the dependence of the properties of chemical elements and simple substances with their atomic masses. Currently, the law has been refined, and the dependence of the properties is explained by the charge of the atomic nucleus.

The law was discovered by a Russian scientist in 1869. Mendeleev presented it to the scientific community in a report to the congress of the Russian Chemical Society (the report was made by another scientist, since Mendeleev was forced to urgently leave on the instructions of the Free Economic Society of St. Petersburg). In the same year, the textbook “Fundamentals of Chemistry” was published, written by Dmitry Ivanovich for students. In it, the scientist described the properties of popular compounds, and also tried to provide a logical systematization of chemical elements. It also presented for the first time a table with periodically arranged elements, as a graphic interpretation of the periodic law. All subsequent years, Mendeleev improved his table, for example, he added a column of inert gases, which were discovered 25 years later.

The scientific community did not immediately accept the ideas of the great Russian chemist, even in Russia. But after three new elements were discovered (gallium in 1875, scandium in 1879 and germanium in 1886), predicted and described by Mendeleev in his famous report, the periodic law was recognized.

  • Is a universal law of nature.
  • The table, which graphically represents the law, includes not only all known elements, but also those that are still being discovered.
  • All new discoveries did not affect the relevance of the law and the table. The table is being improved and changed, but its essence has remained unchanged.
  • Made it possible to clarify the atomic weights and other characteristics of some elements and to predict the existence of new elements.
  • Chemists received a reliable hint on how and where to look for new elements. In addition, the law allows, with a high degree of probability, to determine in advance the properties of yet undiscovered elements.
  • Played a huge role in the development of inorganic chemistry in the 19th century.

History of discovery

There is a beautiful legend that Mendeleev saw his table in a dream, and woke up in the morning and wrote it down. In fact, this is just a myth. The scientist himself said many times that he devoted 20 years of his life to the creation and improvement of the periodic table of elements.

It all started with the fact that Dmitry Ivanovich decided to write a textbook on inorganic chemistry for students, in which he planned to systematize all the knowledge known at that moment. And naturally, he relied on the achievements and discoveries of his predecessors. For the first time, attention to the relationship between atomic weights and the properties of elements was drawn by the German chemist Döbereiner, who tried to divide the elements known to him into triads with similar properties and weights that obey a certain rule. In each triple, the middle element had a weight close to the arithmetic mean of the two outer elements. The scientist was thus able to form five groups, for example, Li–Na–K; Cl–Br–I. But these were not all known elements. In addition, the three elements clearly did not exhaust the list of elements with similar properties. Attempts to find a general pattern were later made by the Germans Gmelin and von Pettenkofer, the French J. Dumas and de Chancourtois, and the English Newlands and Odling. The German scientist Meyer advanced the furthest, who in 1864 compiled a table very similar to the periodic table, but it contained only 28 elements, while 63 were already known.

Unlike his predecessors, Mendeleev succeeded draw up a table that includes all known elements arranged according to a certain system. At the same time, he left some cells blank, approximately calculating the atomic weights of some elements and describing their properties. In addition, the Russian scientist had the courage and foresight to declare that the law he discovered was a universal law of nature and called it “periodic law.” Having said “a,” he went ahead and corrected the atomic weights of the elements that did not fit into the table. Upon closer inspection, it turned out that his corrections were correct, and the discovery of the hypothetical elements he described became the final confirmation of the truth of the new law: practice proved the validity of the theory.

Ministry of Education and Science of the Russian Federation

Department of Education of the Administration of Tver

Municipal educational institution

"Evening (shift) secondary 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 institutions, and 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 for all further development of the doctrine of atoms and elements; they are the foundation of chemistry and physics of our days.

Purpose 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 elements of a completely different chemical behavior were 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 in common with them, fell into the group of oxygen and sulfur. This is how the idea of ​​the periodicity of the properties of elements was first 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 published a work 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 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:

“Emerited Professor Alexander Aleksandrovich Inostrantsev kindly told me extremely interesting things about Mendeleev’s intuition that completes the creative process. 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. For this purpose, I wrote on small pieces of cardboard the signs of the elements and their atomic weights, after which I began to group them in various ways according to their similarity. But this method did not satisfy me until I arranged the cardboards one after the other according to increasing order. atomic weight. When I arranged 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 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 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, because, judging by its name, one could expect that it would finally give an answer to the question that interests 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, which is why it should have been included in the collection of works on periodic law, and not excluded from this collection. As a result of searching for this article, it was discovered. , that in the French journal on 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. a 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.

A closer look at the text of the article published in French shows that this is not some new work, but an exact translation from his article “Periodic Law of Chemical Elements,” which he wrote for the Encyclopedic Dictionary of Brockhaus and Efron, and which was published in Volume XXIII 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 Boblovo estate 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 call these patterns a general law of 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 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-aluminium, eca-boron and eca-silicon. Since the mid-1880s, the Periodic Law has been definitively recognized as one of the theoretical foundations of chemistry.

Conclusion

The periodic law played a huge role in the development of chemistry and other natural sciences. The mutual relationship between all elements and their physical and chemical properties was discovered. This posed a scientific and philosophical problem of enormous importance to natural science: this mutual connection must be explained. After the discovery of the Periodic Law, it became clear that the atoms of all elements should be built according to a single principle, and their structure should 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 of the modern concept of “chemical element” and clarification of 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.”

References

2. . Basics of chemistry. - T. 2. – M. – L.: Goskhimizdat, 1947. - 389 p.

3. . Selected lectures on chemistry. – M.: Higher. school, 1968. - 224 s.

4. . New materials on the history of the discovery of the periodic law. - M.–L.: Publishing house Acad. Sciences USSR, 1950. - 145 s.

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

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