2.2. The history of the creation of the Periodic system.

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

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

The decisive stage of his thoughts came on March 1, 1869 (February 14, old style). A day earlier, Mendeleev wrote a request for a ten-day vacation to inspect artel cheese factories in the Tver province: he received a letter with recommendations on studying cheese production from A. I. Khodnev, one of the leaders of the Free Economic Society.

Petersburg that day was cloudy and frosty. The trees creaked in the wind in the university garden, where the windows of Mendeleev's apartment looked out. While still in bed, Dmitry Ivanovich drank a mug of warm milk, then got up, washed himself and went to breakfast. His mood was wonderful.

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

After breakfast, Mendeleev closed himself in his office. He took out a pack of business cards from the desk and began to write the symbols of the elements and their main chemical properties on their reverse side. After a while, the household heard how it began to be heard from the office: "Uuu! Horned one. Wow, what a horned one! I will overcome them. I will kill them!" These exclamations meant that Dmitry Ivanovich had a creative inspiration. Mendeleev shifted the cards from one horizontal row to another, guided by the values ​​of the atomic mass and the properties of simple substances formed by atoms of the same element. Once again, a thorough knowledge of inorganic chemistry came to his aid. Gradually, the appearance of the future Periodic Table of chemical elements began to take shape. So, at first he put a card with the element beryllium Be (atomic mass 14) next to the card of the aluminum element Al (atomic mass 27.4), according to the then tradition, taking beryllium for an analog of aluminum. However, then, comparing the chemical properties, he placed beryllium over magnesium Mg. Having doubted the then generally accepted value of the atomic mass of beryllium, he changed it to 9.4, and changed the formula of beryllium oxide from Be 2 O 3 to BeO (like magnesium oxide MgO). By the way, the "corrected" value of the atomic mass of beryllium was confirmed only ten years later. He acted just as boldly on other occasions.

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

On the evening of March 1, 1869, he whitewashed the table he had compiled and, under the title "Experiment of a system of elements based on their atomic weight and chemical similarity," sent it to the printer, making notes for typesetters and putting the date "February 17, 1869" (this is according to the old style).

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

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

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

On March 18, 1869, Menshutkin, who at that time was the clerk of the society, made a small report on the Periodic Law on behalf of Mendeleev. The report at first did not attract much attention of chemists, and the President of the Russian Chemical Society, Academician Nikolai Zinin (1812-1880) stated that Mendeleev was not doing what a real researcher should do. True, two years later, after reading Dmitry Ivanovich's article "The natural system of elements and its application to indicating the properties of certain elements," Zinin changed his mind and wrote to Mendeleev: "Very, very good, very excellent approximations, even fun to read, God bless you good luck in experimental confirmation of your conclusions. Sincerely devoted to you and deeply respecting you N. Zinin. Mendeleev did not place all the elements in ascending order of atomic masses; in some cases he was more guided by the similarity of chemical properties. So, cobalt Co has an atomic mass greater than nickel Ni, tellurium Te also has a greater mass than iodine I, but Mendeleev placed them in the order Co - Ni, Te - I, and not vice versa. Otherwise, tellurium would fall into the group of halogens, and iodine would become a relative of selenium Se.

To his wife and children. Or maybe he knew that he was dying, but did not want to disturb and excite the family in advance, whom he loved passionately and tenderly. At 5:20 a.m. January 20, 1907 Dmitry Ivanovich Mendeleev died. He was buried at the Volkovsky cemetery in St. Petersburg, not far from the graves of his mother and son Vladimir. In 1911, the Museum of D.I. Mendeleev, where ...

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

Lyceum exam, where old Derzhavin blessed the young Pushkin. The role of the meter happened to be played by Academician Yu.F. Fritsshe, a well-known specialist in organic chemistry. PhD thesis D.I. Mendeleev graduated from the Main Pedagogical Institute in 1855. PhD thesis "Isomorphism in connection with other relationships of crystalline form to composition" became his first major scientific ...

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

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 pioneer of the table was the Russian scientist Dmitry Mendeleev. An extraordinary scientist with the broadest scientific horizons managed to combine all ideas about the nature of chemical elements into a single coherent concept.

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, M24.RU will tell in this article.

Table opening history

By the middle of the 19th century, 63 chemical elements had been discovered, and scientists around the world have repeatedly attempted to combine all the existing elements into a single concept. The elements were proposed to be placed in ascending order of atomic mass and divided into groups according to the similarity of 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 work of the scientist 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 scheme of the periodic table in the journal of the Russian Chemical Society and sent out a notice of the discovery to the leading scientists of the world. In the future, the chemist repeatedly refined and improved the scheme until it acquired its familiar form.

The essence of Mendeleev's discovery is that with an increase in the atomic mass, the chemical properties of elements do not change monotonously, 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 united 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 fully 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 idea of ​​chemistry and believed that doing chemistry was something like eating soup from babies and stealing on an industrial scale. Therefore, the activities of Mendeleev quickly acquired a mass of rumors and legends.

One of the legends says that Mendeleev discovered the table of chemical elements in his sleep. The case is not the only one, August Kekule, who dreamed of the formula of the benzene ring, spoke in the same way 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 in suddenly ... ready!”, 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 contemporaries of the chemist laughed, saying that the scientist “does well under the influence of alcohol combined with water”, and the next generations already called Mendeleev the discoverer of vodka.

They also laughed at the way of life of the scientist, and especially at the fact that Mendeleev equipped his laboratory in the hollow of a huge oak.

Also, contemporaries teased Mendeleev's passion for suitcases. The scientist, at the time of his involuntary inaction in Simferopol, was forced to pass the time weaving suitcases. In the future, he independently made cardboard containers for the needs of the laboratory. Despite the clearly "amateur" nature of this hobby, Mendeleev was often called a "suitcase master."

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. A 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 is more radioactive than pure uranium.

Since no one knew what radioactivity was then, the 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, 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" lasted for twenty whole years - until the 30s of the twentieth century, when scientists discovered the true properties of radioactivity and found out how detrimental the effect of radiation 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 coherent system, but also made it possible to predict many discoveries of new elements. At the same time, some chemical "elements" were declared 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 new elements of nebulium and coronium.

When studying the solar atmosphere, astronomers discovered spectral lines that they could not identify with any of the chemical elements known on earth. Scientists have suggested that these lines belong to a new element, which was called coronium (because the lines were discovered during the study of the "crown" of the Sun - the outer layer of the star's atmosphere).

A few years later, astronomers made another discovery by 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, since Mendeleev's periodic table no longer had room for elements with the properties of nebulium and coronium. After checking, it was found that nebulium is ordinary terrestrial oxygen, and coronium is highly ionized iron.

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

No, it's not true. A popular legend says that Dmitry Mendeleev, resting after scientific work, suddenly saw in a dream a periodic table of chemical elements. The scientist, stunned by the dream, allegedly immediately woke up and in a fever began to look for a pencil in order to quickly transfer the table from memory to paper. Mendeleev himself treated this fascinating story with ill-concealed irony. He said about his table: “I’ve been thinking about it for maybe twenty years, but you think: I sat and suddenly ... it’s ready.”

Who is the author of the myth about the sleepy nature of Mendeleev's discovery?

Most likely, this bike was born at the suggestion of Alexander Inostrantsev, professor of geology at the University of St. Petersburg. In his numerous letters, he says that he was very friendly with Mendeleev. And once a chemist opened his soul to a geologist, telling him literally the following: “Obviously, I saw a table in a dream in which the elements were arranged as needed. I woke up and immediately wrote down the data on a piece of paper and fell asleep again. And only in one place did it require editing later. Later, Inostrantsev often retold this story to his students, who were very impressed with the idea that in order to make a great discovery, it was enough just to fall asleep deeply.

More critical listeners were in no hurry to take the above anecdote on faith, since, firstly, Inostrantsev was never such a bosom friend of Mendeleev. Secondly, the chemist generally opened up to few people, he often joked with his friends, while doing it with a more than serious expression on his face, so that those around him often could not understand whether this or that phrase was seriously thrown or not. Thirdly, Mendeleev said in his diaries and letters that from 1869 to 1871 he made not one, but many edits in the table.

Were there scientists who made discoveries in their sleep?

Unlike Mendeleev, many foreign scientists and inventors not only did not disown, but, on the contrary, emphasized in every possible way that some kind of insight that descended on them in a dream helped them to make this or that discovery.

American scientist Elias Howe at the end of the 19th century, he worked on the creation of a sewing machine. Howe's first devices broke and spoiled the fabric - this was due to the fact that the needle eye was on the blunt side of the needle. The scientist for a long time could not figure out how to solve this problem, until one day he dozed off right above the drawings. Howe dreamed that the ruler of some overseas country, under pain of death, ordered him to make a sewing machine. The apparatus he created immediately broke down, and the monarch became furious. As Howe was led to the scaffold, he saw that the spears of the guards surrounding him had holes just below the point. Waking up, Howe moved the eye to the opposite end of the needle, and his sewing machine began to work without a hitch.

German chemist Friedrich August Kekule in 1865, he dozed off in his favorite armchair by the fireplace and had the following dream: “Atoms jumped before my eyes, they merged into larger structures, similar to snakes. As if spellbound, I followed their dance, when suddenly one of the "snakes" grabbed its tail and danced teasingly before my eyes. As if pierced by lightning, I woke up: the structure of benzene is a closed ring!

Danish scientist Niels Bor in 1913 he dreamed that he found himself on the Sun, and the planets revolved around him at great speed. Impressed by this dream, Bohr created a planetary model of the structure of atoms, for which he was later awarded the Nobel Prize.

German scientist Otto Levy proved that the nature of the transmission of a nerve impulse in the human body is chemical, and not electrical, as was thought at the beginning of the twentieth century. This is how Levy described his scientific research, which did not stop day or night: “... On the night before Easter Sunday 1920, I woke up and made some notes on a piece of paper. Then I fell asleep again. In the morning I had the feeling that I wrote down something very important that night, but I could not decipher my scribbles. The next night, at three o'clock, the idea came back to me. This was the design of an experiment that would help determine whether my hypothesis of chemical transmission is valid ... I immediately got up, went to the laboratory and set up an experiment on a frog's heart that I saw in a dream ... Its results became the basis of the theory of chemical transmission of a nerve impulse. For his contribution to medicine in 1936, Levy received the Nobel Prize. Two years later he emigrated from Germany, first to the UK and then to the USA. Berlin allowed the scientist to go abroad only after he donated the entire monetary reward to the needs of the Third Reich.

In the middle of the 20th century, an American scientist James Watson I saw in a dream two intertwining snakes. This dream helped him to be the first in the world to depict the shape and structure of DNA.

How to use the periodic table? For an uninitiated person, reading the periodic table is the same as looking at the ancient runes of elves for a dwarf. And the periodic table can tell a lot about the world.

In addition to serving you in the exam, it is also simply indispensable for solving a huge number of chemical and physical problems. But how to read it? Fortunately, today everyone can learn this art. In this article we will tell you how to understand the periodic table.

The periodic system of chemical elements (Mendeleev's table) is a classification of chemical elements that establishes the dependence of various properties of elements on the charge of the atomic nucleus.

History of the creation of the Table

Dmitri Ivanovich Mendeleev was not a simple chemist, if someone thinks so. He was a chemist, physicist, geologist, metrologist, ecologist, economist, oilman, aeronaut, instrument maker and teacher. During his life, the scientist managed to conduct a lot of fundamental research in various fields of knowledge. For example, it is widely believed that it was Mendeleev who calculated the ideal strength of vodka - 40 degrees.

We do not know how Mendeleev treated vodka, but it is known for sure that his dissertation on the topic “Discourse on the combination of alcohol with water” had nothing to do with vodka and considered alcohol concentrations from 70 degrees. With all the merits of the scientist, the discovery of the periodic law of chemical elements - one of the fundamental laws of nature, brought him the widest fame.

There is a legend according to which the scientist dreamed of the periodic system, after which he only had to finalize the idea that had appeared. But, if everything were so simple .. This version of the creation of the periodic table, apparently, is nothing more than a legend. When asked how the table was opened, Dmitry Ivanovich himself answered: “ I’ve been thinking about it for maybe twenty years, and you think: I sat and suddenly ... it’s ready. ”

In the middle of the nineteenth century, attempts to streamline the known chemical elements (63 elements were known) were simultaneously undertaken by several scientists. For example, in 1862 Alexandre Émile Chancourtois placed the elements along a helix and noted the cyclical repetition of chemical properties.

Chemist and musician John Alexander Newlands proposed his version of the periodic table in 1866. An interesting fact is that in the arrangement of the elements the scientist tried to discover some mystical musical harmony. Among other attempts was the attempt of Mendeleev, which was crowned with success.

In 1869, the first scheme of the table was published, and the day of March 1, 1869 is considered the day of the discovery of the periodic law. The essence of Mendeleev's discovery was that the properties of elements with increasing atomic mass do not change monotonously, but periodically.

The first version of the table contained only 63 elements, but Mendeleev made a number of very non-standard decisions. So, he guessed to leave a place in the table for yet undiscovered elements, and also changed the atomic masses of some elements. The fundamental correctness of the law derived by Mendeleev was confirmed very soon, after the discovery of gallium, scandium and germanium, the existence of which was predicted by scientists.

Modern view of the periodic table

Below is the table itself.

Today, instead of atomic weight (atomic mass), the concept of atomic number (the number of protons in the nucleus) is used to order elements. The table contains 120 elements, which are arranged from left to right in ascending order of atomic number (number of protons)

The columns of the table are so-called groups, and the rows are periods. There are 18 groups and 8 periods in the table.

1. The metallic properties of the elements decrease when moving along the period from left to right, and increase in the opposite direction.
2. The dimensions of atoms decrease as they move from left to right along the periods.
3. When moving from top to bottom in the group, the reducing metallic properties increase.
4. Oxidizing and non-metallic properties increase along the period from left to right.

What do we learn about the element from the table? For example, let's take the third element in the table - lithium, and consider it in detail.

First of all, we see the symbol of the element itself and its name under it. In the upper left corner is the atomic number of the element, in the order in which the element is located in the table. The atomic number, as already mentioned, is equal to the number of protons in the nucleus. The number of positive protons is usually equal to the number of negative electrons in an atom (with the exception of isotopes).

The atomic mass is indicated under the atomic number (in this version of the table). If we round the atomic mass to the nearest integer, we get the so-called mass number. The difference between the mass number and the atomic number gives the number of neutrons in the nucleus. Thus, the number of neutrons in a helium nucleus is two, and in lithium - four.

So our course "Mendeleev's Table for Dummies" has ended. In conclusion, we invite you to watch a thematic video, and we hope that the question of how to use the periodic table of Mendeleev has become more clear to you. We remind you that learning a new subject is always more effective not alone, but with the help of an experienced mentor. That is why, you should never forget about the student service, which will gladly share their knowledge and experience with you.

Instruction

The periodic system is a multi-storey "house" in which a large number of apartments are located. Each "tenant" or in his own apartment under a certain number, which is permanent. In addition, the element has a "surname" or name, such as oxygen, boron or nitrogen. In addition to these data, each "apartment" or information such as relative atomic mass is indicated, which may have exact or rounded values.

As in any house, there are "entrances", namely groups. Moreover, in groups, elements are located on the left and right, forming . Depending on which side there are more of them, that side is called the main one. The other subgroup, respectively, will be secondary. Also in the table there are "floors" or periods. Moreover, the periods can be both large (consist of two rows) and small (they have only one row).

According to the table, you can show the structure of the atom of an element, each of which has a positively charged nucleus, consisting of protons and neutrons, as well as negatively charged electrons rotating around it. The number of protons and electrons coincides numerically and is determined in the table by the ordinal number of the element. For example, the chemical element sulfur has #16, so it will have 16 protons and 16 electrons.

To determine the number of neutrons (neutral particles also located in the nucleus), subtract its serial number from the relative atomic mass of an element. For example, iron has a relative atomic mass of 56 and an atomic number of 26. Therefore, 56 - 26 = 30 protons in iron.

The electrons are located at different distances from the nucleus, forming electronic levels. To determine the number of electronic (or energy) levels, you need to look at the number of the period in which the element is located. For example, aluminum is in period 3, so it will have 3 levels.

By the group number (but only for the main subgroup), you can determine the highest valence. For example, the elements of the first group of the main subgroup (lithium, sodium, potassium, etc.) have a valence of 1. Accordingly, the elements of the second group (beryllium, magnesium, calcium, etc.) will have a valence of 2.

You can also analyze the properties of elements using the table. From left to right, the metallic properties decrease and the non-metallic properties increase. This is clearly seen in the example of period 2: it begins with an alkali metal sodium, then an alkaline earth metal magnesium, after it an amphoteric element aluminum, then non-metals silicon, phosphorus, sulfur, and the period ends with gaseous substances - chlorine and argon. In the next period, a similar dependence is observed.

From top to bottom, a pattern is also observed - metallic properties are enhanced, and non-metallic ones are weakened. That is, for example, cesium is much more active than sodium.