Meaning of the periodic table. The meaning of the periodic law Signs of the periodic system and the periodic law

Discovery by D.I. Mendeleev's periodic law is of great importance for the development of chemistry. The law was the scientific basis of chemistry. The author managed to systematize the rich, but scattered material accumulated by generations of chemists on the properties of elements and their compounds, and clarify many concepts, for example, the concepts of “chemical element” and “simple substance”. In addition, D.I. Mendeleev predicted the existence and described with amazing accuracy the properties of many elements unknown at that time, for example, scandium (eca-boron), gallium (eka-aluminium), germanium (eca-silicon). In a number of cases, based on the periodic law, the scientist changed the atomic masses of elements accepted at that time ( Zn, La, I, Er, Ce, Th,U), which were previously determined on the basis of erroneous ideas about the valence of elements and the composition of their compounds. In some cases, Mendeleev arranged elements in accordance with a natural change in properties, suggesting a possible inaccuracy in the values ​​​​of their atomic masses ( Os, Ir, Pt, Au, Te, I, Ni, Co) and for some of them, as a result of subsequent refinement, the atomic masses were corrected.

The periodic law and the periodic table of elements serve as the scientific basis for prediction in chemistry. Since the publication of the periodic table, more than 40 new elements have appeared in it. Based on the periodic law, transuranium elements were artificially obtained, including No. 101, called mendelevium.

The periodic law played a decisive role in elucidating the complex structure of the atom. We must not forget that the law was formulated by the author in 1869, i.e. almost 60 years before the modern theory of atomic structure was finally formed. And all the discoveries of scientists that followed the publication of the law and the periodic system of elements (we talked about them at the beginning of the presentation of the material) served as confirmation of the brilliant discovery of the great Russian chemist, his extraordinary erudition and intuition.

LITERATURE

1. Glinka N. A. General chemistry / N. A. Glinka. L.: Chemistry, 1984. 702 p.

2. Course of general chemistry / ed. N.V. Korovina. M.: Higher School, 1990. 446 p.

3. Akhmetov N.S. general and inorganic chemistry / N.S. Akhmetov. M.: Higher School, 1988. 639 p.

4. Pavlov N.N. Inorganic chemistry / N.N. Pavlov. M.: Higher School, 1986. 336 p.

5. Ramsden E.N. The beginnings of modern chemistry / E.N. Ramsden. L.: Chemistry, 1989. 784 p.

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The periodic law and the periodic system of chemical elements of D. I. Mendeleev based on ideas about the structure of atoms. The importance of the periodic law for the development of science

Chemistry tickets for the 10th grade course.

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The periodic law and the periodic system of chemical elements of D. I. Mendeleev based on ideas about the structure of atoms. The importance of the periodic law for the development of science.

In 1869, D.I. Mendeleev, based on an analysis of the properties of simple substances and compounds, formulated the Periodic Law:

The properties of simple bodies... and compounds of elements are periodically dependent on the magnitude of the atomic masses of the elements.

Based on the periodic law, the periodic system of elements was compiled. In it, elements with similar properties were combined into vertical columns - groups. In some cases, when placing elements in the Periodic Table, it was necessary to disrupt the sequence of increasing atomic masses in order to maintain the periodicity of the repetition of properties. For example, we had to “swap” tellurium and iodine, as well as argon and potassium.

The reason is that Mendeleev proposed the periodic law at a time when nothing was known about the structure of the atom.

After the planetary model of the atom was proposed in the 20th century, the periodic law was formulated as follows:

The properties of chemical elements and compounds periodically depend on the charges of atomic nuclei.

The charge of the nucleus is equal to the number of the element in the periodic table and the number of electrons in the electron shell of the atom.

This formulation explained the "violations" of the Periodic Law.

In the Periodic Table, the period number is equal to the number of electronic levels in the atom, the group number for elements of the main subgroups is equal to the number of electrons in the outer level.

The reason for the periodic change in the properties of chemical elements is the periodic filling of electron shells. After filling the next shell, a new period begins. The periodic change of elements is clearly visible in the changes in the composition and properties of the oxides.

Scientific significance of the periodic law. The periodic law made it possible to systematize the properties of chemical elements and their compounds. When compiling the periodic table, Mendeleev predicted the existence of many undiscovered elements, leaving empty cells for them, and predicted many properties of undiscovered elements, which facilitated their discovery.

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7. Periodic law and periodic system D.I. Mendeleev Structure of the periodic system (period, group, subgroup). The meaning of the periodic law and the periodic system.

Periodic law of D.I. Mendeleev The properties of simple bodies, as well as the forms and properties of compounds of elements, are periodically dependent on. values ​​of atomic weights of elements

Periodic table of elements. Series of elements within which properties change sequentially, such as the series of eight elements from lithium to neon or from sodium to argon, Mendeleev called periods. If we write these two periods one below the other so that sodium is under lithium and argon is under neon, we get the following arrangement of elements:

With this arrangement, the vertical columns contain elements that are similar in their properties and have the same valency, for example, lithium and sodium, beryllium and magnesium, etc.

Having divided all the elements into periods and placing one period under another so that elements similar in properties and type of compounds formed were located under each other, Mendeleev compiled a table that he called the periodic system of elements by groups and series.

Meaning of the periodic table. The periodic table of elements had a great influence on the subsequent development of chemistry. Not only was it the first natural classification of chemical elements, showing that they form a harmonious system and are in close connection with each other, but it was also a powerful tool for further research.

8. Periodic changes in the properties of chemical elements. Atomic and ionic radii. Ionization energy. Electron affinity. Electronegativity.

The dependence of atomic radii on the charge of the nucleus of an atom Z is periodic. Within one period, with increasing Z, there is a tendency for the size of the atom to decrease, which is especially clearly observed in short periods

With the beginning of the construction of a new electronic layer, more distant from the nucleus, i.e., during the transition to the next period, atomic radii increase (compare, for example, the radii of fluorine and sodium atoms). As a result, within a subgroup, with increasing nuclear charge, the sizes of atoms increase.

The loss of electron atoms leads to a decrease in its effective size^ and the addition of excess electrons leads to an increase. Therefore, the radius of a positively charged ion (cation) is always smaller, and the radius of a negatively charged non (anion) is always greater than the radius of the corresponding electrically neutral atom.

Within one subgroup, the radii of ions of the same charge increase with increasing nuclear charge. This pattern is explained by an increase in the number of electronic layers and the growing distance of outer electrons from the nucleus.

The most characteristic chemical property of metals is the ability of their atoms to easily give up external electrons and transform into positively charged ions, while non-metals, on the contrary, are characterized by the ability to add electrons to form negative ions. To remove an electron from an atom and transform the latter into a positive ion, it is necessary to expend some energy, called ionization energy.

Ionization energy can be determined by bombarding atoms with electrons accelerated in an electric field. The lowest field voltage at which the electron speed becomes sufficient to ionize atoms is called the ionization potential of the atoms of a given element and is expressed in volts.

With the expenditure of sufficient energy, two, three or more electrons can be removed from an atom. Therefore, they speak of the first ionization potential (the energy of the removal of the first electron from the atom) and the second ionization potential (the energy of the removal of the second electron)

As noted above, atoms can not only donate, but also gain electrons. The energy released when an electron attaches to a free atom is called the atom's electron affinity. Electron affinity, like ionization energy, is usually expressed in electron volts. Thus, the electron affinity of the hydrogen atom is 0.75 eV, oxygen - 1.47 eV, fluorine - 3.52 eV.

The electron affinities of metal atoms are typically close to zero or negative; It follows from this that for atoms of most metals the addition of electrons is energetically unfavorable. The electron affinity of nonmetal atoms is always positive and the greater, the closer the nonmetal is located to the noble gas in the periodic table; this indicates an increase in non-metallic properties as the end of the period approaches.

(?)9. Chemical bond. Basic types and characteristics of chemical bonds. Conditions and mechanism of its formation. Valence bond method. Valence. Concept of the molecular orbital method

When atoms interact, a chemical bond can arise between them, leading to the formation of a stable polyatomic system - a molecule, a molecular non, a crystal. the condition for the formation of a chemical bond is a decrease in the potential energy of the system of interacting atoms.

Theory of chemical structure. The basis of the theory developed by A. M. Butlerov is the following:

Atoms in molecules are connected to each other in a certain sequence. Changing this sequence leads to the formation of a new substance with new properties.

The combination of atoms occurs in accordance with their valence.

The properties of substances depend not only on their composition, but also on their “chemical structure,” that is, on the order of connection of atoms in molecules and the nature of their mutual influence. The atoms that are directly connected to each other most strongly influence each other.

The ideas about the mechanism of chemical bond formation, developed by Heitler and London using the example of the hydrogen molecule, were extended to more complex molecules. The theory of chemical bonds developed on this basis was called the valence bond method (BC method). The BC method provided a theoretical explanation of the most important properties of covalent bonds and made it possible to understand the structure of a large number of molecules. Although, as we will see below, this method did not turn out to be universal and in some cases is not able to correctly describe the structure and properties of molecules, it still played a large role in the development of the quantum mechanical theory of chemical bonding and has not lost its importance to this day. Valence is a complex concept. Therefore, there are several definitions of valency, expressing different aspects of this concept. The following definition can be considered the most general: the valency of an element is the ability of its atoms to combine with other atoms in certain ratios.

Initially, the valency of the hydrogen atom was taken as the unit of valence. The valency of another element can be expressed by the number of hydrogen atoms that adds to itself or replaces one atom of this other element.

We already know that the state of the electrodes in an atom is described by quantum mechanics as a set of atomic electron orbitals (atomic electron clouds); Each such orbital is characterized by a certain set of atomic quantum numbers. The MO method is based on the assumption that the state of electrons in a molecule can also be described as a set of molecular electron orbitals (molecular electron clouds), with each molecular orbital (MO) corresponding to a specific set of molecular quantum numbers. As in any other multielectron system, the Pauli principle remains valid in the molecule (see § 32), so that each MO can contain no more than two electrons, which must have oppositely directed spins.

The importance of the periodic law for the development of science

Based on the Periodic Law, Mendeleev compiled a classification of chemical elements - the periodic system. It consists of 7 periods and 8 groups.
The periodic law marked the beginning of the modern stage of development of chemistry. With its discovery, it became possible to predict new elements and describe their properties.
With the help of the Periodic Law, atomic masses were corrected and the valences of some elements were clarified; the law reflects the interconnection of elements and the interdependence of their properties. The periodic law confirmed the most general laws of the development of nature and opened the way to knowledge of the structure of the atom.

The periodic table of elements had a great influence on the subsequent development of chemistry.

Dmitry Ivanovich Mendeleev (1834-1907)

Not only was it the first natural classification of chemical elements, showing that they form a harmonious system and are in close connection with each other, but it also became a powerful tool for further research.

At the time when Mendeleev compiled his table based on the periodic law he discovered, many elements were still unknown. Thus, the fourth period element scandium was unknown. In terms of atomic mass, titanium came after calcium, but titanium could not be placed immediately after calcium, since it would fall into the third group, while titanium forms a higher oxide, and according to other properties it should be classified in the fourth group. Therefore, Mendeleev skipped one cell, that is, he left free space between calcium and titanium. On the same basis, in the fourth period, two free cells were left between zinc and arsenic, now occupied by the elements gallium and germanium. There are still empty seats in other rows. Mendeleev was not only convinced that there must be as yet unknown elements that would fill these spaces, but he also predicted the properties of such elements in advance based on their position among other elements of the periodic table. He gave the name ekabor to one of them, which in the future was to take a place between calcium and titanium (since its properties were supposed to resemble boron); the other two, for which there were spaces left in the table between zinc and arsenic, were named eka-aluminum and eca-silicon.

Over the next 15 years, Mendeleev's predictions were brilliantly confirmed: all three expected elements were discovered. First, the French chemist Lecoq de Boisbaudran discovered gallium, which has all the properties of eka-aluminium; then, in Sweden, L. F. Nilsson discovered scandium, which had the properties of ekaboron, and finally, a few years later in Germany, K. A. Winkler discovered an element he called germanium, which turned out to be identical to ekasilicon.

To judge the amazing accuracy of Mendeleev’s foresight, let us compare the properties of eca-silicon predicted by him in 1871 with the properties of germanium discovered in 1886:

The discovery of gallium, scandium and germanium was the greatest triumph of the periodic law.

The periodic system was also of great importance in establishing the valence and atomic masses of some elements. Thus, the element beryllium has long been considered an analogue of aluminum and its oxide was assigned the formula. Based on the percentage composition and the expected formula of beryllium oxide, its atomic mass was considered to be 13.5. The periodic table has shown that there is only one place for beryllium in the table, namely above magnesium, so its oxide must have the formula , which gives the atomic mass of beryllium equal to ten. This conclusion was soon confirmed by determinations of the atomic mass of beryllium from the vapor density of its chloride.

Exactly And at present, the periodic law remains the guiding thread and guiding principle of chemistry. It was on its basis that transuranium elements located in the periodic table after uranium were artificially created in recent decades. One of them - element No. 101, first obtained in 1955 - was named mendelevium in honor of the great Russian scientist.

The discovery of the periodic law and the creation of a system of chemical elements was of great importance not only for chemistry, but also for philosophy, for our entire understanding of the world. Mendeleev showed that chemical elements form a harmonious system, which is based on a fundamental law of nature. This is an expression of the position of materialist dialectics about the interconnection and interdependence of natural phenomena. Revealing the relationship between the properties of chemical elements and the mass of their atoms, the periodic law was a brilliant confirmation of one of the universal laws of the development of nature - the law of the transition of quantity into quality.

The subsequent development of science made it possible, based on the periodic law, to understand the structure of matter much more deeply than was possible during Mendeleev’s lifetime.

The theory of atomic structure developed in the 20th century, in turn, gave the periodic law and the periodic system of elements a new, deeper illumination. The prophetic words of Mendeleev were brilliantly confirmed: “The periodic law is not threatened with destruction, but only superstructure and development are promised.”

The periodic law and the periodic system of chemical elements in the light of the theory of atomic structure

March 1, 1869Formulation of the periodic law by D.I. Mendeleev.

The properties of simple substances, as well as the forms and properties of compounds of elements, are periodically dependent on the atomic weights of the elements.

Back at the end of the 19th century, D.I. Mendeleev wrote that, apparently, the atom consists of other smaller particles, and the periodic law confirms this.

Modern formulation of the periodic law.

The properties of chemical elements and their compounds are periodically dependent on the magnitude of the charge of the nuclei of their atoms, expressed in the periodic repeatability of the structure of the outer valence electron shell.

Periodic law in the light of the theory of atomic structure

The periodic table in the light of the theory of atomic structure

Conclusions:

1. The fewer electrons on the outer level and the larger the radius of the atom, the lower the electronegativity and the easier it is to give up outer electrons, therefore, the more pronounced the metallic properties are.

The more electrons in the outer level and the smaller the radius of the atom, the greater the electronegativity and the easier it is to accept electrons, therefore, the stronger the non-metallic properties.

2. Metals are characterized by giving up electrons, while non-metals are characterized by receiving electrons.

The special position of hydrogen in the periodic table

Hydrogen in the periodic table occupies two cells (in one of them it is enclosed in brackets) - in group 1 and in group 7.

Hydrogen is in the first group because, like the elements of the first group, it has one electron at the outer level.

Hydrogen is in the seventh group because, like the elements of the seventh group, before the completion of the energy

THE MEANING OF THE PERIODIC LAW

The periodic table of elements has become one of the most valuable generalizations in chemistry. It is like a summary of the chemistry of all elements, a graph from which you can read the properties of the elements and their compounds. The system made it possible to clarify the position, atomic masses, and valency values ​​of some elements. Based on the table, it was possible to predict the existence and properties of yet undiscovered elements. Mendeleev formulated the periodic law and proposed its graphical representation, but at that time it was impossible to determine the nature of periodicity. The meaning of the periodic law was revealed later, in connection with discoveries on the structure of the atom.

1. In what year was the periodic law discovered?

2. What did Mendeleev take as the basis for the systematization of elements?

3. What does the law discovered by Mendeleev say?

4. What is the difference with the modern formulation?

5. What is called an atomic orbital?

6. How do properties change over periods?

7. How are periods divided?

8. What is a group called?

9. How are groups divided?

10. What types of electrons do you know?

11. How do energy levels fill?

Lecture No. 4: Valency and oxidation state. Frequency of property changes.

Origin of the concept of valency. The valence of chemical elements is one of their most important properties. The concept of valence was introduced into science by E. Frankland in 1852. At first, the concept was exclusively stoichiometric in nature and stemmed from the law of equivalents. The meaning of the concept of valence follows from a comparison of the values ​​of atomic mass and the equivalent of chemical elements.

With the establishment of atomic-molecular concepts, the concept of valence acquired a certain structural and theoretical meaning. Valency began to be understood as the ability of one atom of a given element to attach to itself a certain number of atoms of another chemical element. The corresponding capacity of the hydrogen atom was taken as the unit of valence, since the ratio of the atomic mass of hydrogen to its equivalent is equal to unity. Thus, the valency of a chemical element was defined as the ability of its atom to attach a certain number of hydrogen atoms. If a given element did not form compounds with hydrogen, its valence was determined as the ability of its atom to replace a certain number of hydrogen atoms in its compounds.

This idea of ​​valence was confirmed for the simplest compounds.

Based on the idea of ​​the valence of elements, the idea of ​​the valence of entire groups arose. So, for example, the OH group, since it added one hydrogen atom or replaced one hydrogen atom in its other compounds, was assigned a valence of one. However, the idea of ​​valency lost its unambiguity when it came to more complex compounds. So, for example, in hydrogen peroxide H 2 O 2 the valency of oxygen should be recognized as equal to one, since in this compound there is one hydrogen atom for each oxygen atom. However, it is known that each oxygen atom in H 2 O 2 is connected to one hydrogen atom and one monovalent OH group, i.e. oxygen is divalent. Similarly, the valency of carbon in ethane C 2 H 6 should be recognized as equal to three, since in this compound there are three hydrogen atoms for each carbon atom, but since each carbon atom is connected to three hydrogen atoms and one monovalent group CH 3, the valence carbon in C 2 H 6 is equal to four.

It should be noted that when forming ideas about the valence of individual elements, these complicating circumstances were not taken into account, and only the composition of the simplest compounds was taken into account. But even at the same time, it turned out that for many elements the valency in different compounds is not the same. This was especially noticeable for compounds of some elements with hydrogen and oxygen, in which different valences appeared. Thus, in combination with hydrogen, the valency of sulfur turned out to be equal to two, and with oxygen – six. Therefore, they began to distinguish between hydrogen valence and oxygen valency.

Subsequently, in connection with the idea that in compounds some atoms are polarized positively and others negatively, the concept of valence in oxygen and hydrogen compounds was replaced by the concept of positive and negative valency.

Different valence values ​​for the same elements were also manifested in their different compounds with oxygen. In other words, the same elements were able to exhibit different positive valence. This is how the idea of ​​variable positive valence of some elements appeared. As for the negative valence of non-metallic elements, it, as a rule, turned out to be constant for the same elements.

The majority of elements exhibited variable positive valence. However, each of these elements was characterized by its maximum valency. This maximum valency is called characteristic.

Later, in connection with the emergence and development of the electronic theory of atomic structure and chemical bonds, valence began to be associated with the number of electrons passing from one atom to another, or with the number of chemical bonds that arise between atoms in the process of formation of a chemical compound.

Electrovalency and covalency. The positive or negative valence of an element is most easily determined if two elements formed an ionic compound: the element whose atom became a positively charged ion was considered to have a positive valence, and the element whose atom became a negatively charged ion had a negative valence. The numerical value of valence was considered equal to the magnitude of the ion charge. Since ions in compounds are formed by the donation and acquisition of electrons by atoms, the amount of charge of the ions is determined by the number of electrons given up (positive) and added (negative) by the atoms. In accordance with this, the positive valence of an element was measured by the number of electrons donated by its atom, and the negative valence - by the number of electrons attached by a given atom. Thus, since valence was measured by the magnitude of the electric charge of atoms, it received the name electrovalency. It is also called ionic valency.

Among chemical compounds there are those in whose molecules the atoms are not polarized. Obviously, for them the concept of positive and negative electrovalency is not applicable. If the molecule is composed of atoms of one element (elementary substances), the usual concept of stoichiometric valency loses its meaning. However, in order to evaluate the ability of atoms to attach a given number of other atoms, they began to use the number of chemical bonds that arise between a given atom and other atoms during the formation of a chemical compound. Since these chemical bonds, which are electron pairs simultaneously belonging to both connected atoms, are called covalent, the ability of an atom to form a certain number of chemical bonds with other atoms is called covalency. To establish covalency, structural formulas are used in which chemical bonds are represented by dashes.

Oxidation state and oxidation number. In reactions of the formation of ionic compounds, the transition of electrons from one reacting atoms or ions to others is accompanied by a corresponding change in the value or sign of their electrovalence. When compounds of a covalent nature are formed, such a change in the electrovalent state of the atoms actually does not occur, but only a redistribution of electronic bonds takes place, and the valence of the original reacting substances does not change. Currently, to characterize the state of an element in connections, a conditional concept has been introduced oxidation states. The numerical expression of the oxidation state is called oxidation number.

The oxidation numbers of atoms can have positive, zero and negative values. A positive oxidation number is determined by the number of electrons drawn from a given atom, and a negative oxidation number is determined by the number of electrons attracted by a given atom. The oxidation number can be assigned to each atom in any substance, for which you need to be guided by the following simple rules:

1. The oxidation numbers of atoms in any elementary substances are zero.

2. The oxidation numbers of elementary ions in substances of ionic nature are equal to the values ​​of the electrical charges of these ions.

3. The oxidation numbers of atoms in compounds of a covalent nature are determined by the conventional calculation that each electron drawn from an atom gives it a charge equal to +1, and each electron attracted gives it a charge equal to –1.

4. The algebraic sum of the oxidation numbers of all atoms of any compound is zero.

5. The fluorine atom in all its compounds with other elements has an oxidation number of –1.

The determination of the oxidation state is associated with the concept of electronegativity of elements. Using this concept, another rule is formulated.

6. In compounds, the oxidation number is negative for atoms of elements with higher electronegativity and positive for atoms of elements with lower electronegativity.

The concept of oxidation state has thus replaced the concept of electrovalence. In this regard, it seems inappropriate to use the concept of covalency. To characterize elements, it is better to use the concept of valence, defining it by the number of electrons used by a given atom to form electron pairs, regardless of whether they are attracted to a given atom or, conversely, withdrawn from it. Then the valence will be expressed as an unsigned number. In contrast to valence, the oxidation state is determined by the number of electrons drawn from a given atom (positive), or attracted to it (negative). In many cases, the arithmetic values ​​of valency and oxidation state coincide - this is quite natural. In some cases, the numerical values ​​of valency and oxidation state differ from each other. For example, in molecules of free halogens the valence of both atoms is equal to one, and the oxidation state is zero. In the molecules of oxygen and hydrogen peroxide, the valency of both oxygen atoms is two, and their oxidation state in the oxygen molecule is zero, and in the hydrogen peroxide molecule it is minus one. In the molecules of nitrogen and hydrazine - N 4 H 2 - the valency of both nitrogen atoms is three, and the oxidation state in the elemental nitrogen molecule is zero, and in the hydrazine molecule it is minus two.

It is obvious that valence characterizes atoms that are only part of any compound, even a homonuclear one, that is, consisting of atoms of one element; It makes no sense to talk about the valence of individual atoms. The degree of oxidation characterizes the state of atoms both included in a compound and existing separately.

Questions to reinforce the topic:

1. Who introduced the concept of “valence”?

2. What is valency called?

3. What is the difference between valency and oxidation state?

4. What is the valency?

5. How is the oxidation state determined?

6. Are the valency and oxidation state of an element always equal?

7. By which element is the valence of an element determined?

8. What characterizes the valence of an element, and what is the oxidation state?

9. Can the valence of an element be negative?

Lecture No. 5: The rate of a chemical reaction.

Chemical reactions can vary significantly in the time they take to occur. A mixture of hydrogen and oxygen at room temperature can remain virtually unchanged for a long time, but if struck or ignited, an explosion will occur. The iron plate slowly rusts, and a piece of white phosphorus spontaneously ignites in air. It is important to know how quickly a particular reaction occurs in order to be able to control its progress.

Scientific significance of the periodic law. Life and work of D.I. Mendeleev

The discovery of the periodic law and the creation of the Periodic Table of Chemical Elements is the greatest achievement of science of the 19th century. Experimental confirmation of the relative atomic masses changed by D.I. Mendeleev, the discovery of elements with the properties envisaged by him, and the location of open inert gases in the periodic table led to the universal recognition of the periodic law.

The discovery of the periodic law led to further rapid development of chemistry: over the next thirty years, 20 new chemical elements were discovered. The periodic law contributed to the further development of work on the study of the structure of the atom, as a result of which the relationship between the structure of the atom and the periodic change of their properties was established. Based on the periodic law, scientists were able to extract substances with given properties and synthesize new chemical elements. The periodic law has allowed scientists to build hypotheses about the evolution of chemical elements in the Universe.

The periodic law of D.I. Mendeleev has general scientific significance and is a fundamental law of nature.

Dmitry Ivanovich Mendeleev was born in 1834 in Tobolsk. After graduating from the Tobolsk gymnasium, he studied at the St. Petersburg Pedagogical Institute, from which he graduated with a gold medal. As a student, D.I. Mendeleev began to engage in scientific research. After studying, he spent two years abroad in the laboratory of the famous chemist Robert Bunsen. In 1863, he was elected professor, first at the St. Petersburg Institute of Technology, and subsequently at St. Petersburg University.

Mendeleev conducted research in the field of the chemical nature of solutions, the state of gases, and the heat of combustion of fuel. He was interested in various problems of agriculture, mining, metallurgy issues, worked on the problem of underground gasification of fuel, and studied petroleum engineering. The most significant result of creative activity, which brought D. I. Mendeleev worldwide fame, was the discovery in 1869 of the Periodic Law and the Periodic Table of Chemical Elements. He wrote about 500 articles on chemistry, physics, technology, economics, and geodesy. He organized and was the director of the first Russian Chamber of Weights and Measures, and concluded the beginning of modern metrology. Invented the general equation of state of an ideal gas, generalized the Clapeyron equation (Clapeyron-Mendeleev equation).

Mendeleev lived to be 73 years old. For his achievements, he was elected a member of 90 foreign academies of sciences and honorary doctorates of many universities. The 101st chemical element (Mendelevium) is named in his honor.