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 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.

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 TYRAN” 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 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”).

Many have also heard that D.I. Mendeleev was the organizer and permanent leader (1869-1905) of the Russian public scientific association called “Russian Chemical Society” (since 1872 - “Russian Physico-Chemical Society”), which throughout its existence published the world-famous journal ZhRFKhO, until 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:

At this time, it officially contains 118 chemicals. Of these, 94 were found in nature, the remaining 24 were obtained artificially as a result of nuclear reactions. Of all the chemicals found in nature, 88; elements such as technetium Tc, promethium Pm, astatine At and France Fr, as well as all the elements following uranium U, were obtained artificially for the first time. Under normal conditions, the corresponding simple substances for 11 elements are gases, for 2 - liquids, for the remaining elements - solids.

Worth reading

Dmitri Ivanovich Mendeleev- Russian scientist-encyclopedist, public figure. Chemist, physical chemist, physicist, metrologist, economist, technologist, geologist, meteorologist, teacher, aeronaut, instrument maker. Professor of St. Petersburg University; Corresponding Member in the “Physical” category of the Imperial St. Petersburg Academy of Sciences. Among the most famous discoveries is the periodic law of chemical elements, one of the fundamental laws of the universe, integral to all natural science.

Periodic Table of Chemical Elements– classification of chemical elements, establishing the dependence of various properties of elements on the charge of the atomic nucleus. The system is a graphic expression of the periodic law established by the Russian chemist D.I. Mendeleev in 1869. Its initial version was developed by D.I. Mendeleev in 1869-1871 and established the dependence of the properties of elements on their atomic weight. In total, several hundred options for depicting the periodic table have been proposed. In the modern version of the system, it is assumed that the elements are summarized in a two-dimensional table, in which each column defines the main physical and chemical properties, and the rows represent periods that are to a certain extent similar to each other. By the middle of the 19th century, 63 chemical elements had been discovered, and attempts to find patterns in this set were made repeatedly. More common than others are 3 forms of the periodic table: “short”, “long” and “extra-long”. In the “super-long” version, each period occupies exactly one line. Periodic system D.I. Mendeleev became a major milestone in the development of atomic-molecular science.

A new element has been added to the periodic table

Instructions

The periodic system is a multi-story “house” containing a large number of apartments. 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 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 its atomic number from the relative atomic mass of the element. 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 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 increase, and non-metallic properties 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 of chemical elements D.I. 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 remained unclear for a long time. 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 under normal conditions the atom is 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

The periodic law, which is the basis of modern chemistry and explains 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 by studying the complex structure of the atom.

In the 19th century, it was believed that atomic mass was the main characteristic of an 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 non-metallicity 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.

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 (numbered 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 an essential 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 its mechanical properties. In the chemical industry, selenium is used as a catalyst.

Sources:

• KhiMiK.ru, Selen

Calcium is a chemical element belonging to the second subgroup of the periodic table with the symbol 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

From Latin, “” is translated 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 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, which is why it is practically never found in nature in its pure form. 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. This element is found 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, through the migration of this element in the 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, which is why 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. The most famous story at that time was the discovery of such new elements as coronium and nebulium.

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 “The Natural System of 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. The modern version consists of 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 valence is and determine other chemical characteristics. 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 correctness and accuracy of the periodic system, the scientific community did not want to recognize this discovery for a long time. 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. The modern concept of an element was formed precisely thanks to the great scientist. The advent of Mendeleev's periodic system introduced fundamental changes in the understanding of various compounds 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.

Even at school, sitting in chemistry lessons, we all remember the table on the wall of the classroom or chemical laboratory. This table contained a classification of all chemical elements known to mankind, those fundamental components that make up the Earth and the entire Universe. Then we could not even think that Mendeleev table is undoubtedly one of the greatest scientific discoveries, which is the foundation of our modern knowledge of chemistry.

Periodic table of chemical elements by D. I. Mendeleev

At first glance, her idea looks deceptively simple: organize chemical elements in order of increasing weight of their atoms. Moreover, in most cases it turns out that the chemical and physical properties of each element are similar to the element preceding it in the table. This pattern appears for all elements except the very first few, simply because they do not have in front of them elements similar to them in atomic weight. It is thanks to the discovery of this property that we can place a linear sequence of elements in a table much like a wall calendar, and thus combine a huge number of types of chemical elements in a clear and coherent form. Of course, today we use the concept of atomic number (the number of protons) in order to order the system of elements. This helped solve the so-called technical problem of a “pair of permutations”, but did not lead to a fundamental change in the appearance of the periodic table.

IN periodic table all elements are ordered based on their atomic number, electronic configuration, and repeating chemical properties. The rows in the table are called periods, and the columns are called groups. The first table, dating back to 1869, contained only 60 elements, but now the table had to be enlarged to accommodate the 118 elements we know today.

Mendeleev's periodic table systematizes not only the elements, but also their most diverse properties. It is often enough for a chemist to have the Periodic Table in front of his eyes in order to correctly answer many questions (not only exam questions, but also scientific ones).

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Periodic law

There are two formulations periodic law chemical elements: classical and modern.

Classical, as presented by its discoverer D.I. Mendeleev: the properties of simple bodies, as well as the forms and properties of compounds of elements, are periodically dependent on the values ​​of the atomic weights of the elements.

Modern: the properties of simple substances, as well as the properties and forms of compounds of elements, are periodically dependent on the charge of the nucleus of the atoms of the elements (ordinal number).

A graphic representation of the periodic law is the periodic system of elements, which is a natural classification of chemical elements based on regular changes in the properties of elements depending on the charges of their atoms. The most common images of the periodic table of elements are D.I. Mendeleev's forms are short and long.

Groups and periods of the Periodic Table

In groups are called vertical rows in the periodic table. In groups, elements are combined based on the highest oxidation state in their oxides. Each group consists of a main and secondary subgroup. The main subgroups include elements of small periods and elements of large periods with the same properties. Side subgroups consist only of elements of large periods. The chemical properties of the elements of the main and secondary subgroups differ significantly.

Period called a horizontal row of elements arranged in order of increasing atomic numbers. There are seven periods in the periodic system: the first, second and third periods are called small, they contain 2, 8 and 8 elements, respectively; the remaining periods are called large: in the fourth and fifth periods there are 18 elements, in the sixth - 32, and in the seventh (not yet completed) - 31 elements. Each period, except the first, begins with an alkali metal and ends with a noble gas.

Physical meaning of the serial number chemical element: the number of protons in the atomic nucleus and the number of electrons rotating around the atomic nucleus are equal to the atomic number of the element.

Properties of the periodic table

Let us remind you that groups are called vertical rows in the periodic table and the chemical properties of the elements of the main and secondary subgroups differ significantly.

The properties of elements in subgroups naturally change from top to bottom:

• metallic properties increase and non-metallic properties weaken;
• the atomic radius increases;
• the strength of bases and oxygen-free acids formed by the element increases;
• electronegativity decreases.

All elements except helium, neon and argon form oxygen compounds; there are only eight forms of oxygen compounds. In the periodic table, they are often depicted by general formulas, located under each group in increasing order of the oxidation state of the elements: R 2 O, RO, R 2 O 3, RO 2, R 2 O 5, RO 3, R 2 O 7, RO 4, where the symbol R denotes an element of this group. The formulas of higher oxides apply to all elements of the group, except in exceptional cases when the elements do not exhibit an oxidation state equal to the group number (for example, fluorine).

Oxides of the composition R 2 O exhibit strong basic properties, and their basicity increases with increasing atomic number; oxides of the composition RO (with the exception of BeO) exhibit basic properties. Oxides of the composition RO 2, R 2 O 5, RO 3, R 2 O 7 exhibit acidic properties, and their acidity increases with increasing atomic number.

The elements of the main subgroups, starting from group IV, form gaseous hydrogen compounds. There are four forms of such compounds. They are located under the elements of the main subgroups and are represented by general formulas in the sequence RH 4, RH 3, RH 2, RH.

RH 4 compounds are neutral in nature; RH 3 - weakly basic; RH 2 - slightly acidic; RH - strongly acidic character.

Let us remind you that period called a horizontal row of elements arranged in order of increasing atomic numbers.

Within a period with increasing element serial number:

• electronegativity increases;
• metallic properties decrease, non-metallic properties increase;
• the atomic radius decreases.

Elements of the periodic table

Alkali and alkaline earth elements

These include elements from the first and second groups of the periodic table. Alkali metals from the first group - soft metals, silver in color, easy to cut with a knife. They all have a single electron in their outer shell and react perfectly. Alkaline earth metals from the second group also have a silvery tint. Two electrons are placed at the outer level, and, accordingly, these metals interact less readily with other elements. Compared to alkali metals, alkaline earth metals melt and boil at higher temperatures.

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Lanthanides (rare earth elements) and actinides

Lanthanides- a group of elements originally found in rare minerals; hence their name "rare earth" elements. Subsequently, it turned out that these elements are not as rare as initially thought, and therefore the name lanthanides was given to rare earth elements. Lanthanides and actinides occupy two blocks, which are located under the main table of elements. Both groups include metals; all lanthanides (except promethium) are non-radioactive; actinides, on the contrary, are radioactive.

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Halogens and noble gases

The halogens and noble gases are grouped into groups 17 and 18 of the periodic table. Halogens are non-metallic elements, they all have seven electrons in their outer shell. IN noble gases All the electrons are in the outer shell, so they hardly participate in the formation of compounds. These gases are called “noble” gases because they rarely react with other elements; that is, they refer to members of the noble caste who have traditionally shunned other people in society.

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Transition metals

Transition metals occupy groups 3-12 in the periodic table. Most of them are dense, hard, with good electrical and thermal conductivity. Their valence electrons (with the help of which they are connected to other elements) are located in several electron shells.

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Metalloids

Metalloids occupy groups 13-16 of the periodic table. Metalloids such as boron, germanium and silicon are semiconductors and are used to make computer chips and circuit boards.

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Post-transition metals

Elements called post-transition metals, belong to groups 13-15 of the periodic table. Unlike metals, they do not have shine, but have a matte color. Compared to transition metals, post-transition metals are softer, have lower melting and boiling points, and higher electronegativity. Their valence electrons, with which they attach other elements, are located only on the outer electron shell. Post-transition metal group elements have much higher boiling points than metalloids.

Now consolidate your knowledge by watching a video about the periodic table and more.

Great, the first step on the path to knowledge has been taken. Now you are more or less oriented in the periodic table and this will be very useful to you, because the Periodic System of Mendeleev is the foundation on which this amazing science stands.