Instructions

Periodic table is a multi-storey “house” containing a large number of apartments. Each “tenant” or in his own 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 this data, each “apartment” contains information such as relative atomic mass, which may have exact or rounded values.

As in any house, there are “entrances”, namely groups. Moreover, in groups the 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, accordingly, will be secondary. The table also has “floors” or periods. Moreover, periods can be both large (consist of two rows) and small (have only one row).

The table shows the structure of an 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 is numerically the same and is determined in the table by the serial number of the element. For example, the chemical element sulfur is #16, therefore it will have 16 protons and 16 electrons.

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

Electrons are located at different distances from the nucleus, forming electron 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, it is in the 3rd period, therefore it will have 3 levels.

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

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

From top to bottom there is also a pattern - metallic properties strengthen, and non-metallic weaken. That is, for example, cesium is much more active compared to sodium.

Helpful advice

For convenience, it is better to use the color version of the table.

Discovery of the periodic law and creation of an ordered system chemical elements DI. Mendeleev became the apogee of the development of chemistry in the 19th century. The scientist summarized and systematized extensive knowledge about the properties of elements.

Instructions

In the 19th century there was no idea about the structure of the atom. Discovery by D.I. Mendeleev was only a generalization of experimental facts, but their physical meaning for a long time remained unclear. When the first data appeared on the structure of the nucleus and the distribution of electrons in atoms, it was possible to look at the law and system of elements in a new way. Table D.I. Mendeleev makes it possible to visually trace the properties of the elements found in.

Each element in the table is assigned a specific serial number (H - 1, Li - 2, Be - 3, etc.). This number corresponds to the nucleus (the number of protons in the nucleus) and the number of electrons orbiting the nucleus. The number of protons is thus equal to the number of electrons, which means that in normal conditions atom electrically.

The division into seven periods occurs according to the number of energy levels of the atom. Atoms of the first period have a single-level electron shell, the second - a two-level, the third - a three-level, etc. When a new energy level is filled, a new period begins.

The first elements of any period are characterized by atoms that have one electron at the outer level - these are alkali metal atoms. The periods end with atoms of noble gases, which have an external energy level completely filled with electrons: in the first period, noble gases have 2 electrons, in subsequent periods - 8. It is precisely because of the similar structure of the electron shells that groups of elements have similar physics.

In the table D.I. Mendeleev has 8 main subgroups. This number is determined by the maximum possible number of electrons at the energy level.

At the bottom of the periodic table, lanthanides and actinides are distinguished as independent series.

Using the table D.I. Mendeleev, one can observe the periodicity of the following properties of elements: atomic radius, atomic volume; ionization potential; electron affinity forces; electronegativity of the atom; ; physical properties of potential compounds.

Clearly traceable periodicity of the arrangement of elements in the table D.I. Mendeleev is rationally explained by the sequential nature of filling energy levels with electrons.

Sources:

Mendeleev table

Periodic law, which is the basis modern chemistry and explaining the patterns of changes in the properties of chemical elements, was discovered by D.I. Mendeleev in 1869. The physical meaning of this law is revealed when studying complex structure atom.

In the 19th century it was believed that atomic mass is main characteristic element, so it was used to classify substances. Nowadays, atoms are defined and identified by the amount of charge on their nucleus (the number and atomic number on the periodic table). However, the atomic mass of elements, with some exceptions (for example, the atomic mass is less than the atomic mass of argon), increases in proportion to their nuclear charge.

With an increase in atomic mass, a periodic change in the properties of elements and their compounds is observed. These are the metallicity and nonmetallicity of atoms, atomic radius, ionization potential, electron affinity, electronegativity, oxidation states, compounds (boiling points, melting points, density), their basicity, amphotericity or acidity.

How many elements are in the modern periodic table

The periodic table graphically expresses the law he discovered. The modern periodic table contains 112 chemical elements (the last ones are Meitnerium, Darmstadtium, Roentgenium and Copernicium). According to the latest data, the following 8 elements have also been discovered (up to 120 inclusive), but not all of them have received their names, and these elements are still few in any printed publications are present.

Each element occupies a specific cell in the periodic table and has its own serial number, corresponding to the charge of the nucleus of its atom.

How is the periodic table constructed?

The structure of the periodic table is represented by seven periods, ten rows and eight groups. Each period begins with an alkali metal and ends with a noble gas. The exceptions are the first period, which begins with hydrogen, and the seventh incomplete period.

Periods are divided into small and large. Small periods (first, second, third) consist of one horizontal row, large periods (fourth, fifth, sixth) - of two horizontal rows. The upper rows in large periods are called even, the lower rows are called odd.

In the sixth period of the table after (serial number 57) there are 14 elements similar in properties to lanthanum - lanthanides. They are listed at the bottom of the table as a separate line. The same applies to actinides located after actinium (with number 89) and largely repeating its properties.

The even rows of large periods (4, 6, 8, 10) are filled only with metals.

Elements in groups exhibit the same valency in oxides and other compounds, and this valency corresponds to the group number. The main ones contain elements of small and large periods, only large ones. From top to bottom they strengthen, non-metallic ones weaken. All atoms of side subgroups are metals.

Tip 4: Selenium as a chemical element on the periodic table

The chemical element selenium belongs to group VI of the periodic table of Mendeleev, it is a chalcogen. Natural selenium consists of six stable isotopes. There are also 16 radioactive isotopes of selenium known.

Instructions

Selenium is considered a very rare and trace element; it migrates vigorously in the biosphere, forming more than 50 minerals. The most famous of them are: berzelianite, naumannite, native selenium and chalcomenite.

Selenium is found in volcanic sulfur, galena, pyrite, bismuthin and other sulfides. It is mined from lead, copper, nickel and other ores, in which it is found in a dispersed state.

The tissues of most living beings contain from 0.001 to 1 mg/kg; some plants, marine organisms and fungi concentrate it. For a number of plants, selenium is necessary element. The need for humans and animals is 50-100 mcg/kg of food; this element has antioxidant properties, affects many enzymatic reactions and increases the sensitivity of the retina to light.

Selenium can exist in various allotropic modifications: amorphous (vitreous, powdery and colloidal selenium), as well as crystalline. By reducing selenium from a solution of selenous acid or by rapidly cooling its vapor, red powdered and colloidal selenium is obtained.

When any modification of this chemical element is heated above 220°C and subsequently cooled, glassy selenium is formed; it is fragile and has a glassy luster.

The most thermally stable is hexagonal gray selenium, the lattice of which is built from spiral chains of atoms located parallel to each other. It is produced by heating other forms of selenium until melting and slowly cooling to 180-210°C. Within hexagonal selenium chains, the atoms are bonded covalently.

Selenium is stable in air, it is not affected by: oxygen, water, dilute sulfuric and hydrochloric acids, but it dissolves well in nitric acid. Interacting with metals, selenium forms selenides. There are many known complex compounds of selenium, all of them are poisonous.

Selenium is obtained from paper or production waste by electrolytic refining of copper. This element is present in sludge along with heavy metals, sulfur and tellurium. To extract it, the sludge is filtered, then heated with concentrated sulfuric acid or subjected to oxidative roasting at a temperature of 700°C.

Selenium is used in the production of rectifying semiconductor diodes and other converter equipment. In metallurgy, it is used to give steel a fine-grained structure and also improve it mechanical properties. IN chemical industry Selenium is used as a catalyst.

Sources:

KhiMiK.ru, Selen

Calcium is a chemical element belonging to the second subgroup periodic table with the symbolic designation Ca and an atomic mass of 40.078 g/mol. It is a fairly soft and reactive alkaline earth metal with a silvery color.

Instructions

WITH Latin language“” translates as “lime” or “soft stone”, and it owes its discovery to the Englishman Humphry Davy, who in 1808 was able to isolate calcium using the electrolytic method. The scientist then took a mixture of wet slaked lime, “flavored” with mercuric oxide, and subjected it to the process of electrolysis on a platinum plate, which appeared in the experiment as an anode. The cathode was a wire that the chemist immersed in liquid mercury. It is also interesting that calcium compounds such as limestone, marble and gypsum, as well as lime, were known to mankind many centuries before Davy’s experiment, during which time scientists believed some of them to be simple and independent bodies. It was not until 1789 that the Frenchman Lavoisier published a work in which he suggested that lime, silica, barite and alumina were complex substances.

Calcium has a high degree of chemical activity, due to which it pure form practically never found in nature. But scientists estimate that this element accounts for about 3.38% of the total mass of the entire earth's crust, making calcium fifth most abundant after oxygen, silicon, aluminum and iron. There is this element in sea water– about 400 mg per liter. Calcium is also included in the composition of silicates of various rocks (for example, granite and gneisses). There is a lot of it in feldspar, chalk and limestones, consisting of the mineral calcite with the formula CaCO3. The crystalline form of calcium is marble. In total, by migrating this element to earth's crust it forms 385 minerals.

The physical properties of calcium include its ability to exhibit valuable semiconducting abilities, although it does not become a semiconductor and a metal in the traditional sense of the word. This situation changes with a gradual increase in pressure, when calcium is given a metallic state and the ability to exhibit superconducting properties. Calcium easily interacts with oxygen, air moisture and carbon dioxide, due to which in laboratories this chemical element is kept tightly closed for work and chemist John Alexander Newland - however, the scientific community ignored his achievement. Newland's proposal was not taken seriously because of his search for harmony and the connection between music and chemistry.

Dmitri Mendeleev first published his periodic table in 1869 in the pages of the Journal of the Russian Chemical Society. The scientist also sent notices of his discovery to all the world's leading chemists, after which he repeatedly improved and finalized the table until it became what it is known today. The essence of Dmitry Mendeleev's discovery was a periodic, rather than monotonous change in the chemical properties of elements with increasing atomic mass. The final unification of the theory into the periodic law occurred in 1871.

Legends about Mendeleev

The most common legend is the discovery of the periodic table in a dream. The scientist himself has repeatedly ridiculed this myth, claiming that he had been coming up with the table for many years. According to another legend, Dmitry Mendeleev vodka - it appeared after the scientist defended his dissertation “Discourse on the combination of alcohol with water.”

Mendeleev is still considered by many to be the discoverer, who himself loved to create under an aqueous-alcohol solution. The scientist’s contemporaries often laughed at Mendeleev’s laboratory, which he set up in the hollow of a giant oak tree.

A separate reason for jokes, according to rumors, was Dmitry Mendeleev’s passion for weaving suitcases, which the scientist was engaged in while living in Simferopol. Later, he made crafts from cardboard for the needs of his laboratory, for which he was sarcastically called a master of suitcase making.

The periodic table, in addition to ordering chemical elements into a single system, made it possible to predict the discovery of many new elements. However, at the same time, scientists recognized some of them as non-existent, since they were incompatible with the concept. Most known history at that time there was the discovery of such new elements as coronium and nebulium.

Classified sections of the periodic table June 15th, 2018

Many have heard about Dmitry Ivanovich Mendeleev and about the “Periodic Law of Changes in the Properties of Chemical Elements in Groups and Series” that he discovered in the 19th century (1869) (the author’s name for the table is “Periodic System of Elements in Groups and Series”).

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.

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 unified 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 leading world 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 Chemical properties 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 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.

But not everything is so simple and there are some things we don’t know.

Few people know that D.I. Mendeleev was one of the first world-famous Russian scientists of the late 19th century, who defended in world science the idea of ether as a universal substantial entity, who gave it fundamental scientific and applied significance in revealing the secrets of Existence and to improve the economic life of people.

There is an opinion that the periodic table of chemical elements officially taught in schools and universities is a falsification. Mendeleev himself, in his work entitled “An Attempt at a Chemical Understanding of the World Ether,” gave a slightly different table.

The last time the real Periodic Table was published in an undistorted form was in 1906 in St. Petersburg (textbook “Fundamentals of Chemistry”, VIII edition).

The differences are visible: the zero group has been moved to the 8th, and the element lighter than hydrogen, with which the table should begin and which is conventionally called Newtonium (ether), is completely excluded.

The same table is immortalized by the "BLOODY TYRANT" comrade. Stalin in St. Petersburg, Moskovsky Avenue. 19. VNIIM im. D. I. Mendeleeva (All-Russian Research Institute of Metrology)

The monument-table of the Periodic Table of Chemical Elements by D. I. Mendeleev was made with mosaics under the direction of Professor of the Academy of Arts V. A. Frolov (architectural design by Krichevsky). The monument is based on a table from the last lifetime 8th edition (1906) of D. I. Mendeleev’s Fundamentals of Chemistry. Elements discovered during the life of D.I. Mendeleev are indicated in red. Elements discovered from 1907 to 1934 , indicated in blue.

Why and how did it happen that they lie to us so brazenly and openly?

The place and role of the world ether in the true table of D. I. Mendeleev

Many have also heard that D.I. Mendeleev was the organizer and permanent leader (1869-1905) of the Russian public scientific association under the name “Russian Chemical Society” (since 1872 - “Russian Physico-Chemical Society”), which published the world-famous journal ZHRFKhO throughout its existence, until the liquidation of both the Society and its journal by the USSR Academy of Sciences in 1930.
But few people know that D.I. Mendeleev was one of the last world-famous Russian scientists of the late 19th century, who defended in world science the idea of ether as a universal substantial entity, who gave it fundamental scientific and applied significance in revealing secrets Being and to improve the economic life of people.

There are even fewer who know that after the sudden (!!?) death of D.I. Mendeleev (01/27/1907), then recognized as an outstanding scientist by all scientific communities around the world except the St. Petersburg Academy of Sciences, his main discovery was “Periodic law” - was deliberately and widely falsified by world academic science.

And there are very few who know that all of the above is connected together by the thread of sacrificial service of the best representatives and bearers of the immortal Russian Physical Thought for the good of the people, the public benefit, despite the growing wave of irresponsibility in the highest strata of society of that time.

In essence, the present dissertation is devoted to the comprehensive development of the last thesis, because in true science, any neglect of essential factors always leads to false results.

Elements of the zero group begin each row of other elements, located on the left side of the Table, “... which is a strictly logical consequence of understanding the periodic law” - Mendeleev.

A particularly important and even exclusive place in the sense of the periodic law belongs to the element “x”—“Newtonium”—to the world ether. And this special element should be located at the very beginning of the entire Table, in the so-called “zero group of the zero row”. Moreover, being a system-forming element (more precisely, a system-forming essence) of all elements of the Periodic Table, the world ether is the substantial argument of the entire diversity of elements of the Periodic Table. The Table itself, in this regard, acts as a closed functional of this very argument.

Sources:

How it all began?

Many famous eminent chemists at the turn of the 19th and 20th centuries have long noticed that the physical and chemical properties of many chemical elements are very similar to each other. For example, Potassium, Lithium and Sodium are all active metals that, when reacting with water, form active hydroxides of these metals; Chlorine, Fluorine, Bromine in their compounds with hydrogen showed the same valency equal to I and all these compounds are strong acids. From this similarity, the conclusion has long been suggested that all known chemical elements can be combined into groups, and so that the elements of each group have a certain set of physical and chemical characteristics. However, such groups were often incorrectly composed of different elements by various scientists and for a long time, many ignored one of the main characteristics of elements - their atomic mass. It was ignored because there were and are different various elements, which means it could not be used as a parameter for combining into groups. The only exception was the French chemist Alexandre Emile Chancourtois, he tried to arrange all the elements in a three-dimensional model along a helix, but his work was not recognized by the scientific community, and the model turned out to be bulky and inconvenient.

Unlike many scientists, D.I. Mendeleev took atomic mass (in those days still “Atomic weight”) as a key parameter in the classification of elements. In his version, Dmitry Ivanovich arranged the elements in increasing order of their atomic weights, and here a pattern emerged that at certain intervals of elements their properties periodically repeat. True, exceptions had to be made: some elements were swapped and did not correspond to the increase in atomic masses (for example, tellurium and iodine), but they corresponded to the properties of the elements. The further development of atomic-molecular science justified such advances and showed the validity of this arrangement. You can read more about this in the article “What is Mendeleev’s discovery”

As we can see, the arrangement of elements in this version is not at all the same as what we see in its modern form. Firstly, the groups and periods are swapped: groups horizontally, periods vertically, and secondly, there are somehow too many groups in it - nineteen, instead of the accepted eighteen today.

However, just a year later, in 1870, Mendeleev formed new option table, which is already more recognizable to us: similar elements are arranged vertically, forming groups, and 6 periods are located horizontally. What is especially noteworthy is that in both the first and second versions of the table one can see significant achievements that his predecessors did not have: the table carefully left places for elements that, in Mendeleev’s opinion, had yet to be discovered. The corresponding vacant positions are indicated by a question mark and you can see them in the picture above. Subsequently, the corresponding elements were actually discovered: Galium, Germanium, Scandium. Thus, Dmitry Ivanovich not only systematized the elements into groups and periods, but also predicted the discovery of new, not yet known, elements.

Subsequently, after solving many pressing mysteries of chemistry of that time - the discovery of new elements, the isolation of a group of noble gases together with the participation of William Ramsay, the establishment of the fact that Didymium is not at all an independent element, but is a mixture of two others - more and more new and new table options, sometimes even having a non-tabular appearance. But we will not present them all here, but will present only the final version, which was formed during the life of the great scientist.

Transition from atomic weights to nuclear charge.

Unfortunately, Dmitry Ivanovich did not live to see the planetary theory of atomic structure and did not see the triumph of Rutherford’s experiments, although it was with his discoveries that a new era began in the development of the periodic law and the entire periodic system. Let me remind you that from experiments conducted by Ernest Rutherford, it followed that the atoms of elements consist of a positively charged atomic nucleus and negatively charged electrons revolving around the nucleus. After determining the charges of the atomic nuclei of all elements known at that time, it turned out that in the periodic table they are located in accordance with the charge of the nucleus. And the periodic law acquired a new meaning, now it began to sound like this:

“The properties of chemical elements, as well as the forms and properties of the simple substances and compounds they form, are periodically dependent on the magnitude of the charges of the nuclei of their atoms”

Now it has become clear why some lighter elements were placed by Mendeleev behind their heavier predecessors - the whole point is that they are so ranked in order of the charges of their nuclei. For example, tellurium is heavier than iodine, but is listed earlier in the table, because the charge of the nucleus of its atom and the number of electrons is 52, while that of iodine is 53. You can look at the table and see for yourself.

After the discovery of the structure of the atom and the atomic nucleus, the periodic table underwent several more changes until it finally reached the form already familiar to us from school, the short-period version of the periodic table.

In this table we are already familiar with everything: 7 periods, 10 rows, secondary and main subgroups. Also, with the time of discovering new elements and filling the table with them, it was necessary to place elements like Actinium and Lanthanum in separate rows, all of them were named Actinides and Lanthanides, respectively. This version of the system existed for a very long time - in the world scientific community almost until the late 80s, early 90s, and in our country even longer - until the 10s of this century.

A modern version of the periodic table.

However, the option that many of us went through in school turns out to be quite confusing, and the confusion is expressed in the division of subgroups into main and secondary ones, and remembering the logic for displaying the properties of elements becomes quite difficult. Of course, despite this, many studied using it, becoming doctors of chemical sciences, but in modern times it has been replaced by a new version - the long-period one. I note that this particular option is approved by IUPAC (International Union of Pure and Applied Chemistry). Let's take a look at it.

Eight groups have been replaced by eighteen, among which there is no longer any division into main and secondary, and all groups are dictated by the location of electrons in the atomic shell. At the same time, we got rid of double-row and single-row periods; now all periods contain only one row. Why is this option convenient? Now the periodicity of the properties of elements is more clearly visible. The group number, in fact, indicates the number of electrons in the outer level, and therefore all the main subgroups of the old version are located in the first, second and thirteenth to eighteenth groups, and all the “former side” groups are located in the middle of the table. Thus, the table now clearly shows that if this is the first group, then this alkali metals and no copper or silver for you, and it is clear that all transit metals clearly demonstrate the similarity of their properties due to the filling of the d-sublevel, which has a lesser effect on external properties, as well as lanthanides and actinides, exhibit similar properties due to only the different f-sublevel. Thus, the entire table is divided into the following blocks: s-block, on which s-electrons are filled, d-block, p-block and f-block, with d, p, and f-electrons filled respectively.

Unfortunately, in our country this option has been included in school textbooks only in the last 2-3 years, and even then not in all of them. And in vain. What is this connected with? Well, firstly, with the stagnant times in the dashing 90s, when there was no development at all in the country, not to mention the education sector, and it was in the 90s that the world chemical community switched to this option. Secondly, with slight inertia and difficulty in perceiving everything new, because our teachers are accustomed to the old, short-period version of the table, despite the fact that when studying chemistry it is much more complex and less convenient.

An extended version of the periodic table.

But time does not stand still, and neither do science and technology. The 118th element of the periodic table has already been discovered, which means that we will soon have to open the next, eighth, period of the table. In addition, a new energy sublevel will appear: the g-sublevel. Its constituent elements will have to be moved down the table, like the lanthanides or actinides, or this table will have to be expanded twice more, so that it will no longer fit on an A4 sheet. Here I will only provide a link to Wikipedia (see Extended Periodic Table) and will not repeat the description of this option once again. Anyone interested can follow the link and get acquainted.

In this version, neither f-elements (lanthanides and actinides) nor g-elements ("elements of the future" from Nos. 121-128) are placed separately, but make the table 32 cells wider. Also, the element Helium is placed in the second group, since it is part of the s-block.

In general, it is unlikely that future chemists will use this option; most likely, the periodic table will be replaced by one of the alternatives that are already being put forward by brave scientists: the Benfey system, Stewart’s “Chemical Galaxy” or another option. But this will only happen after reaching the second island of stability of chemical elements and, most likely, more will be needed for clarity in nuclear physics, than in chemistry, but for now the good old periodic system of Dmitry Ivanovich will suffice.

The nineteenth century in the history of mankind is a century in which many sciences were reformed, including chemistry. It was at this time that Mendeleev's periodic system appeared, and with it the periodic law. It was he who became the basis of modern chemistry. The periodic system of D.I. Mendeleev is a systematization of elements that establishes the dependence of chemical and physical properties on the structure and charge of the atom of a substance.

Story

The beginning of the periodic period was laid by the book “The Correlation of Properties with the Atomic Weight of Elements,” written in the third quarter of the 17th century. It displayed the basic concepts of the known chemical elements (at that time there were only 63 of them). In addition, the atomic masses of many of them were determined incorrectly. This greatly interfered with the discovery of D.I. Mendeleev.

Dmitry Ivanovich began his work by comparing the properties of elements. First of all, he worked on chlorine and potassium, and only then moved on to working with alkali metals. Armed with special cards on which chemical elements were depicted, he repeatedly tried to assemble this “mosaic”: laying it out on his table in search of the necessary combinations and matches.

After much effort, Dmitry Ivanovich finally found the pattern he was looking for and arranged the elements in periodic rows. Having received as a result empty cells between the elements, the scientist realized that not all chemical elements were known to Russian researchers, and that it was he who must give this world the knowledge in the field of chemistry that had not yet been given by his predecessors.

Everyone knows the myth that the periodic table appeared to Mendeleev in a dream, and he collected the elements into a single system from memory. This is, roughly speaking, a lie. The fact is that Dmitry Ivanovich worked quite long and concentrated on his work, and it exhausted him greatly. While working on the system of elements, Mendeleev once fell asleep. When he woke up, he realized that he had not finished the table and rather continued filling in the empty cells. His acquaintance, a certain Inostrantsev, a university teacher, decided that the periodic table had been dreamed of by Mendeleev and spread this rumor among his students. This is how this hypothesis emerged.

Fame

Mendeleev's chemical elements are a reflection of the periodic law created by Dmitry Ivanovich back in the third quarter of the 19th century (1869). It was in 1869 that Mendeleev’s notification about the creation of a certain structure was read out at a meeting of the Russian chemical community. And in the same year, the book “Fundamentals of Chemistry” was published, in which Mendeleev’s periodic system of chemical elements was published for the first time. And in the book " Natural system elements and its use to indicate the qualities of undiscovered elements” D.I. Mendeleev first mentioned the concept of “periodic law”.

Structure and rules for placing elements

The first steps in creating the periodic law were taken by Dmitry Ivanovich back in 1869-1871, at that time he worked hard to establish the dependence of the properties of these elements on the mass of their atom. Modern version represents elements summarized in a two-dimensional table.

The position of an element in the table carries a certain chemical and physical meaning. By the location of an element in the table, you can find out what its valency is and determine other chemical features. Dmitry Ivanovich tried to establish a connection between elements, both similar in properties and differing.

He based the classification of chemical elements known at that time on valence and atomic mass. By comparing the relative properties of elements, Mendeleev tried to find a pattern that would unite all known chemical elements into one system. By arranging them based on increasing atomic masses, he still achieved periodicity in each of the rows.

Further development of the system

The periodic table, which appeared in 1969, has been refined more than once. With the advent of noble gases in the 1930s, it was possible to reveal a new dependence of elements - not on mass, but on atomic number. Later, it was possible to establish the number of protons in atomic nuclei, and it turned out that it coincides with the atomic number of the element. Scientists of the 20th century studied electronic energy. It turned out that it also affects periodicity. This greatly changed ideas about the properties of elements. This point was reflected in later editions of Mendeleev’s periodic table. Each new discovery of the properties and characteristics of elements fit organically into the table.

Characteristics of Mendeleev's periodic system

The periodic table is divided into periods (7 rows arranged horizontally), which, in turn, are divided into large and small. The period begins with an alkali metal and ends with an element with non-metallic properties.
Dmitry Ivanovich's table is vertically divided into groups (8 columns). Each of them in the periodic table consists of two subgroups, namely the main and secondary ones. After much debate, at the suggestion of D.I. Mendeleev and his colleague U. Ramsay, it was decided to introduce the so-called zero group. It includes inert gases (neon, helium, argon, radon, xenon, krypton). In 1911, scientists F. Soddy were asked to place indistinguishable elements, the so-called isotopes, in the periodic table - separate cells were allocated for them.

Despite the truth and accuracy of the periodic system, the scientific community for a long time did not want to recognize this discovery. Many great scientists ridiculed the work of D.I. Mendeleev and believed that it was impossible to predict the properties of an element that had not yet been discovered. But after the supposed chemical elements were discovered (and these were, for example, scandium, gallium and germanium), the Mendeleev system and his periodic law became the science of chemistry.

Table in modern times

Mendeleev's periodic table of elements is the basis of most chemical and physical discoveries related to atomic-molecular science. Modern concept element was formed precisely thanks to the great scientist. The emergence of Mendeleev's periodic system introduced fundamental changes in ideas about various connections and simple substances. The creation of the periodic table by scientists had a huge impact on the development of chemistry and all sciences related to it.

The properties of chemical elements make it possible to combine them into appropriate groups. On this principle, the periodic system was created, which changed the idea of existing substances and made it possible to assume the existence of new, previously unknown elements.

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Mendeleev's periodic table

The periodic table of chemical elements was compiled by D.I. Mendeleev in the second half of the 19th century. What is it and what is it for? It unites all chemical elements in order of increasing atomic weight, and they are all arranged in such a way that their properties change in a periodic manner.

Mendeleev's periodic system brought together into a single system all existing elements, previously considered simply individual substances.

Based on its study, new ones were predicted and subsequently synthesized. chemical substances. The significance of this discovery for science cannot be overestimated, it was significantly ahead of its time and gave impetus to the development of chemistry for many decades.

There are three most common table options, which are conventionally called “short”, “long” and “extra-long” ». The main table is considered to be a long table, it officially approved. The difference between them is the arrangement of elements and the length of periods.

What is a period

The system contains 7 periods. They are presented graphically as horizontal lines. In this case, a period can have one or two lines, called rows. Each subsequent element differs from the previous one by increasing the nuclear charge (number of electrons) by one.

To keep it simple, a period is a horizontal row of the periodic table. Each of them begins with metal and ends with an inert gas. Actually, this creates periodicity - the properties of elements change within one period, repeating again in the next. The first, second and third periods are incomplete, they are called small and contain 2, 8 and 8 elements, respectively. The rest are complete, they have 18 elements each.

What is a group

A group is a vertical column, containing elements with the same electronic structure or, more simply, with the same higher value. The officially approved long table contains 18 groups, which begin with alkali metals and end with noble gases.

Each group has its own name, making it easier to search or classify elements. Metallic properties are enhanced, regardless of the element, from top to bottom. This is due to an increase in the number of atomic orbits - the more there are, the weaker the electronic bonds, which makes the crystal lattice more pronounced.

Metals in the periodic table

Metals in the table Mendeleev have a predominant number, their list is quite extensive. They are characterized common features, according to their properties they are heterogeneous and are divided into groups. Some of them have little in common with metals in the physical sense, while others can exist only for a fraction of a second and are absolutely not found in nature (at least on the planet), since they were created, or rather, calculated and confirmed in laboratory conditions, artificially. Each group has its own characteristics, the name is quite noticeably different from the others. This difference is especially pronounced in the first group.

Position of metals

What is the position of metals in the periodic table? Elements are arranged by increasing atomic mass, or number of electrons and protons. Their properties change periodically, so there is no neat placement on a one-to-one basis in the table. How to identify metals, and is it possible to do this using the periodic table? In order to simplify the question, a special technique was invented: conditionally, a diagonal line is drawn from Bor to Polonius (or to Astatus) at the junctions of the elements. Those on the left are metals, those on the right are non-metals. This would be very simple and cool, but there are exceptions - Germanium and Antimony.

This “methodology” is a kind of cheat sheet; it was invented only to simplify the memorization process. For a more accurate representation, it should be remembered that the list of nonmetals is only 22 elements, therefore, answering the question, how many metals are contained in the periodic table?

In the figure you can clearly see which elements are non-metals and how they are arranged in the table by groups and periods.

General physical properties

There are common physical properties metals These include:

Plastic.
Characteristic shine.
Electrical conductivity.
High thermal conductivity.
All except mercury are in a solid state.

It should be understood that the properties of metals vary greatly regarding their chemical or physical essence. Some of them bear little resemblance to metals in the ordinary sense of the term. For example, mercury occupies a special position. Under normal conditions it is in liquid state, does not have crystal lattice, the presence of which other metals owe their properties. The properties of the latter in this case are conditional; mercury is similar to them to a greater extent in its chemical characteristics.

Interesting! Elements of the first group, alkali metals, are not found in pure form, but are found in various compounds.

The softest metal existing in nature, cesium, belongs to this group. It, like other alkaline substances, has little in common with more typical metals. Some sources claim that in fact, the softest metal is potassium, which is difficult to dispute or confirm, since neither one nor the other element exists on its own - when released as a result of a chemical reaction, they quickly oxidize or react.

The second group of metals - alkaline earth metals - are much closer to the main groups. The name "alkaline earth" comes from ancient times, when oxides were called "earths" because they had a loose, crumbly structure. Metals starting from group 3 have more or less familiar (in the everyday sense) properties. As the group number increases, the amount of metals decreases