The periodic table of chemical elements and its structure. Periodic table D

The brilliant Russian chemist D.I. Mendeleev was distinguished throughout his life by the desire to understand the unknown. This desire, as well as the deepest and most extensive knowledge, combined with unmistakable scientific intuition, allowed Dmitry Ivanovich to develop a scientific classification of chemical elements - the Periodic System in the form of his famous table.

D.I. Mendeleev’s periodic system of chemical elements can be imagined as a large house in which absolutely all the chemical elements known to man “live together.” To be able to use the Periodic Table, you need to study the chemical alphabet, i.e., the signs of chemical elements.

With their help, you will learn to write words - chemical formulas, and on their basis you will be able to write sentences - equations of chemical reactions. Each chemical element is designated by its own chemical sign, or symbol, which, along with the name of the chemical element, is written in D.I. Mendeleev’s table. At the suggestion of the Swedish chemist J. Berzelius, the initial letters of the Latin names of chemical elements were adopted in most cases as symbols. Thus, hydrogen (Latin name Hydrogenium - hydrogenium) is denoted by the letter H (read "ash"), oxygen (Latin name Oxygenium - oxygenium) - by the letter O (read "o"), carbon (Latin name Сarboneum - carboneum) - by the letter C ( read "tse").

The Latin names of several more chemical elements begin with the letter C: calcium (

Calcium), copper (Cuprum), cobalt (Cobaltum), etc. To distinguish them, I. Berzelius proposed adding one of the subsequent letters of the name to the initial letter of the Latin name. Thus, the chemical sign for calcium is written with the symbol Ca (read “calcium”), copper - Cu (read “cuprum”), cobalt - Co (read “cobalt”).

The names of some chemical elements reflect the most important properties of the elements, for example, hydrogen - which produces water, oxygen - which produces acids, phosphorus - which carries light (Fig. 20), etc.

Rice. 20.
Etymology of the name of element No. 15 of the Periodic Table of D. I. Mendeleev

Other elements are named after celestial bodies or planets of the solar system - selenium and tellurium (Fig. 21) (from the Greek Selene - Moon and Telluris - Earth), uranium, neptunium, plutonium.

Rice. 21.
Etymology of the name of element No. 52 of the Periodic Table of D. I. Mendeleev

Some names are borrowed from mythology (Fig. 22). For example, tantalum. This was the name of the beloved son of Zeus. For crimes against the gods, Tantalus was severely punished. He stood up to his neck in water, and branches with juicy, fragrant fruits hung over him. However, as soon as he wanted to drink, the water flowed away from him; as soon as he wanted to satisfy his hunger, he stretched out his hand to the fruits - the branches deviated to the side. Trying to isolate tantalum from ores, chemists experienced no less torment.

Rice. 22.
Etymology of the name of element No. 61 of the Periodic Table of D. I. Mendeleev

Some elements were named after different states or parts of the world. For example, germanium, gallium (Gaul is the ancient name for France), polonium (in honor of Poland), scandium (in honor of Scandinavia), francium, ruthenium (Ruthenium is the Latin name for Russia), europium and americium. Here are the elements named after cities: hafnium (in honor of Copenhagen), lutetium (in the old days Paris was called Lutetium), berkelium (in honor of the city of Berkeley in the USA), yttrium, terbium, erbium, ytterbium (the names of these elements come from Ytterby - small city ​​in Sweden where the mineral containing these elements was first discovered), dubnium (Fig. 23).

Rice. 23.
Etymology of the name of element No. 105 of the Periodic Table of D. I. Mendeleev

Finally, the names of the elements immortalize the names of great scientists: curium, fermium, einsteinium, mendelevium (Fig. 24), lawrencium.

Rice. 24.
Etymology of the name of element No. 101 of the Periodic Table of D. I. Mendeleev

Each chemical element is assigned in the periodic table, in the common “house” of all elements, its own “apartment” - a cell with a strictly defined number. The deeper meaning of this number will be revealed to you as you further study chemistry. The number of floors of these “apartments” is also strictly distributed - the periods in which the elements “live”. Like the serial number of an element (the “apartment” number), the period (“floor”) number contains the most important information about the structure of the atoms of chemical elements. Horizontally - “storeys” - the Periodic Table is divided into seven periods:

• The 1st period includes two elements: hydrogen H and helium He;
• The 2nd period begins with lithium Li and ends with neon Ne (8 elements);
• The 3rd period begins with sodium Na and ends with argon Ar (8 elements).

The first three periods, each consisting of one row, are called small periods.

Periods 4, 5 and 6 each include two rows of elements; they are called large periods; The 4th and 5th periods contain 18 elements each, the 6th - 32 elements.

The 7th period is unfinished, so far it consists of only one row.

Pay attention to the “basement floors” of the Periodic Table - 14 twin elements “live” there, some similar in their properties to lanthanum La, others to actinium Ac, which represent them on the upper “floors” of the table: in the 6th and 7th -th periods.

Vertically, chemical elements “living” in “apartments” with similar properties are located below each other in vertical columns - groups, of which there are eight in D.I. Mendeleev’s table.

Each group consists of two subgroups - main and secondary. The subgroup, which includes elements of both short and long periods, is called the main subgroup or group A. The subgroup, which includes elements of only long periods, is called the secondary subgroup or group B. Thus, the main subgroup of group I (group IA) includes lithium , sodium, potassium, rubidium and francium are a subgroup of lithium Li; a side subgroup of this group (IB group) is formed by copper, silver and gold - this is a subgroup of Cu copper.

In addition to the form of D.I. Mendeleev’s table, which is called short-period (it is shown on the flyleaf of the textbook), there are many other forms, for example, the long-period version.

Just as a child can construct a huge number of different objects from the elements of the Lego game (see Fig. 10), so from chemical elements nature and man have created the variety of substances that surround us. Another model is even more clear: just as 33 letters of the Russian alphabet form various combinations, tens of thousands of words, so 114 chemical elements in various combinations create more than 20 million different substances.

Try to learn the laws of the formation of words - chemical formulas, and then the world of substances will open before you in all its colorful diversity.

But to do this, first learn the letters - symbols of chemical elements (Table 1).

Table 1
Names of some chemical elements

Key words and phrases

1. Periodic table of chemical elements (table) by D. I. Mendeleev.
2. Periods large and small.
3. Groups and subgroups - main (A group) and secondary (B group).
4. Symbols of chemical elements.

Work with computer

1. Refer to the electronic application. Study the lesson material and complete the assigned tasks.
2. Find email addresses on the Internet that can serve as additional sources that reveal the content of keywords and phrases in the paragraph. Offer your help to the teacher in preparing a new lesson - make a report on the key words and phrases of the next paragraph.

Questions and tasks

1. Using dictionaries (etymological, encyclopedic and chemical terms), name the most important properties that are reflected in the names of chemical elements: bromine Br, nitrogen N, fluorine F.
2. Explain how the names of the chemical elements titanium and vanadium reflect the influence of ancient Greek myths.
3. Why is the Latin name for gold Aurum (aurum) and silver - Argentum (argentum)?
4. Tell the story of the discovery of a chemical element of your choice and explain the etymology of its name.
5. Write down the “coordinates”, i.e. the position in the Periodic Table of D.I. Mendeleev (element number, period number and its type - large or small, group number and subgroup - main or minor), for the following chemical elements: calcium, zinc , antimony, tantalum, europium.
6. Distribute the chemical elements listed in Table 1 into three groups based on the “pronunciation of the chemical symbol.” Could doing this activity help you remember chemical symbols and pronounce element symbols?

The periodic system of chemical elements is a classification of chemical elements created by D. I. Mendeleev on the basis of the periodic law discovered by him in 1869.

D. I. Mendeleev

According to the modern formulation of this law, in a continuous series of elements arranged in order of increasing magnitude of the positive charge of the nuclei of their atoms, elements with similar properties periodically repeat.

The periodic table of chemical elements, presented in table form, consists of periods, series and groups.

At the beginning of each period (except for the first), the element has pronounced metallic properties (alkali metal).

Symbols for the color table: 1 - chemical sign of the element; 2 - name; 3 - atomic mass (atomic weight); 4 - serial number; 5 - distribution of electrons across layers.

As the atomic number of an element increases, equal to the positive charge of the nucleus of its atom, metallic properties gradually weaken and non-metallic properties increase. The penultimate element in each period is an element with pronounced non-metallic properties (), and the last is an inert gas. In period I there are 2 elements, in II and III - 8 elements, in IV and V - 18, in VI - 32 and in VII (not completed period) - 17 elements.

The first three periods are called small periods, each of them consists of one horizontal row; the rest - in large periods, each of which (except for the VII period) consists of two horizontal rows - even (upper) and odd (lower). Only metals are found in even rows of large periods. The properties of the elements in these series change slightly with increasing ordinal number. The properties of elements in odd rows of large periods change. In period VI, lanthanum is followed by 14 elements, very similar in chemical properties. These elements, called lanthanides, are listed separately below the main table. Actinides, the elements following actinium, are presented similarly in the table.

The table has nine vertical groups. The group number, with rare exceptions, is equal to the highest positive valency of the elements of this group. Each group, excluding the zero and eighth, is divided into subgroups. - main (located to the right) and secondary. In the main subgroups, as the atomic number increases, the metallic properties of the elements become stronger and the non-metallic properties weaken.

Thus, the chemical and a number of physical properties of elements are determined by the place that a given element occupies in the periodic table.

Biogenic elements, i.e. elements that are part of organisms and perform a certain biological role in it, occupy the top part of the periodic table. Cells occupied by elements that make up the bulk (more than 99%) of living matter are colored blue; cells occupied by microelements are colored pink (see).

The periodic table of chemical elements is the greatest achievement of modern natural science and a vivid expression of the most general dialectical laws of nature.

See also, Atomic weight.

The periodic system of chemical elements is a natural classification of chemical elements created by D. I. Mendeleev on the basis of the periodic law discovered by him in 1869.

In its original formulation, D.I. Mendeleev’s periodic law stated: the properties of chemical elements, as well as the forms and properties of their compounds, are periodically dependent on the atomic weights of the elements. Subsequently, with the development of the doctrine of the structure of the atom, it was shown that a more accurate characteristic of each element is not the atomic weight (see), but the value of the positive charge of the nucleus of the element’s atom, equal to the serial (atomic) number of this element in the periodic system of D. I. Mendeleev . The number of positive charges on the nucleus of an atom is equal to the number of electrons surrounding the nucleus of the atom, since atoms as a whole are electrically neutral. In the light of these data, the periodic law is formulated as follows: the properties of chemical elements, as well as the forms and properties of their compounds, are periodically dependent on the magnitude of the positive charge of the nuclei of their atoms. This means that in a continuous series of elements arranged in order of increasing positive charges of the nuclei of their atoms, elements with similar properties will periodically repeat.

The tabular form of the periodic table of chemical elements is presented in its modern form. It consists of periods, series and groups. A period represents a successive horizontal series of elements arranged in order of increasing positive charge of the nuclei of their atoms.

At the beginning of each period (except for the first) there is an element with pronounced metallic properties (alkali metal). Then, as the serial number increases, the metallic properties of the elements gradually weaken and the non-metallic properties increase. The penultimate element in each period is an element with pronounced non-metallic properties (halogen), and the last is an inert gas. The first period consists of two elements, the role of an alkali metal and a halogen here is simultaneously played by hydrogen. Periods II and III include 8 elements each, called typical by Mendeleev. Periods IV and V contain 18 elements each, VI-32. The VII period has not yet been completed and is replenished with artificially created elements; There are currently 17 elements in this period. Periods I, II and III are called small, each of them consists of one horizontal row, IV-VII are large: they (with the exception of VII) include two horizontal rows - even (upper) and odd (lower). In even rows of large periods there are only metals, and the change in the properties of elements in the row from left to right is weakly expressed.

In odd series of large periods, the properties of the elements in the series change in the same way as the properties of typical elements. In the even row of the VI period, after lanthanum, there are 14 elements [called lanthanides (see), lanthanides, rare earth elements], similar in chemical properties to lanthanum and to each other. A list of them is given separately below the table.

The elements following actinium - actinides (actinoids) - are listed separately and listed below the table.

In the periodic table of chemical elements, nine groups are located vertically. The group number is equal to the highest positive valency (see) of the elements of this group. The exceptions are fluorine (can only be negatively monovalent) and bromine (cannot be heptavalent); in addition, copper, silver, gold can exhibit a valency greater than +1 (Cu-1 and 2, Ag and Au-1 and 3), and of the elements of group VIII, only osmium and ruthenium have a valence of +8. Each group, with the exception of the eighth and zero, is divided into two subgroups: the main one (located to the right) and the secondary one. The main subgroups include typical elements and elements of long periods, the secondary subgroups include only elements of long periods and, moreover, metals.

In terms of chemical properties, the elements of each subgroup of a given group differ significantly from each other, and only the highest positive valence is the same for all elements of a given group. In the main subgroups, from top to bottom, the metallic properties of elements are strengthened and non-metallic ones are weakened (for example, francium is the element with the most pronounced metallic properties, and fluorine is non-metallic). Thus, the place of an element in Mendeleev’s periodic system (ordinal number) determines its properties, which are the average of the properties of neighboring elements vertically and horizontally.

Some groups of elements have special names. Thus, the elements of the main subgroups of group I are called alkali metals, group II - alkaline earth metals, group VII - halogens, elements located behind uranium - transuranium. Elements that are part of organisms, take part in metabolic processes and have a clear biological role are called biogenic elements. All of them occupy the top part of D.I. Mendeleev’s table. These are primarily O, C, H, N, Ca, P, K, S, Na, Cl, Mg and Fe, which make up the bulk of living matter (more than 99%). The places occupied by these elements in the periodic table are colored light blue. Biogenic elements, of which there are very few in the body (from 10 -3 to 10 -14%), are called microelements (see). The cells of the periodic system, colored yellow, contain microelements, the vital importance of which for humans has been proven.

According to the theory of atomic structure (see Atom), the chemical properties of elements depend mainly on the number of electrons in the outer electron shell. The periodic change in the properties of elements with an increase in the positive charge of atomic nuclei is explained by the periodic repetition of the structure of the outer electron shell (energy level) of the atoms.

In small periods, with an increase in the positive charge of the nucleus, the number of electrons in the outer shell increases from 1 to 2 in period I and from 1 to 8 in periods II and III. Hence the change in the properties of elements in the period from an alkali metal to an inert gas. The outer electron shell, containing 8 electrons, is complete and energetically stable (elements of group zero are chemically inert).

In long periods in even rows, as the positive charge of the nuclei increases, the number of electrons in the outer shell remains constant (1 or 2) and the second outer shell is filled with electrons. Hence the slow change in the properties of elements in even rows. In the odd series of large periods, as the charge of the nuclei increases, the outer shell is filled with electrons (from 1 to 8) and the properties of the elements change in the same way as those of typical elements.

The number of electron shells in an atom is equal to the period number. Atoms of elements of the main subgroups have a number of electrons in their outer shells equal to the group number. Atoms of elements of side subgroups contain one or two electrons in their outer shells. This explains the difference in the properties of the elements of the main and secondary subgroups. The group number indicates the possible number of electrons that can participate in the formation of chemical (valence) bonds (see Molecule), therefore such electrons are called valence. For elements of side subgroups, not only the electrons of the outer shells are valence, but also those of the penultimate ones. The number and structure of electron shells are indicated in the accompanying periodic table of chemical elements.

The periodic law of D.I. Mendeleev and the system based on it are of exceptionally great importance in science and practice. The periodic law and system were the basis for the discovery of new chemical elements, the precise determination of their atomic weights, the development of the doctrine of the structure of atoms, the establishment of geochemical laws of distribution of elements in the earth's crust and the development of modern ideas about living matter, the composition of which and the patterns associated with it are in accordance with the periodic system. The biological activity of elements and their content in the body are also largely determined by the place they occupy in Mendeleev’s periodic table. Thus, with an increase in the serial number in a number of groups, the toxicity of elements increases and their content in the body decreases. The periodic law is a clear expression of the most general dialectical laws of the development of nature.

Many scientists have made attempts to systematize chemical elements. But only in 1869 D.I. Mendeleev managed to create a classification of elements that established the connection and dependence of chemical substances and the charge of the atomic nucleus.

Story

The modern formulation of the periodic law is as follows: the properties of chemical elements, as well as the forms and properties of compounds of elements, are periodically dependent on the charge of the nucleus of the atoms of the element.

By the time the law was discovered, 63 chemical elements were known. However, the atomic masses of many of these elements were determined erroneously.

D.I. Mendeleev himself in 1869 formulated his law as a periodic dependence on the atomic weights of elements, since in the 19th century science did not yet have information about the structure of the atom. However, the scientist’s ingenious foresight allowed him to understand more deeply than all his contemporaries the patterns that determine the periodicity of the properties of elements and substances. He took into account not only the increase in atomic mass, but also the already known properties of substances and elements and, taking as a basis the idea of ​​periodicity, he was able to accurately predict the existence and properties of elements and substances unknown to science at that time, correct the atomic masses of a number of elements, and correctly arrange the elements in system, leaving empty spaces and making rearrangements.

Rice. 1. D. I. Mendeleev.

There is a myth that Mendeleev dreamed about the periodic table. However, this is only a beautiful story, which is not a proven fact.

Structure of the periodic table

The periodic table of chemical elements by D.I. Mendeleev is a graphic reflection of his own law. The elements are arranged in the table according to a specific chemical and physical meaning. By the location of an element, you can determine its valence, number of electrons and many other features. The table is divided horizontally into large and small periods, and vertically into groups.

Rice. 2. Periodic table.

There are 7 periods that begin with an alkali metal and end with substances that have non-metallic properties. The groups, in turn, consisting of 8 columns, are divided into main and secondary subgroups.

Further development of science has shown that the periodic repetition of the properties of elements at certain intervals, especially clearly manifested in the 2nd and 3rd small periods, is explained by the repetition of the electronic structure of the outer energy levels, where valence electrons are located, due to which the formation of chemical bonds and new substances occurs in reactions. Therefore, in each vertical column-group there are elements with repeating characteristic features. This is clearly manifested in groups containing families of very active alkali metals (group I, main subgroup) and non-halogen metals (group VII, main subgroup). From left to right across the period, the number of electrons increases from 1 to 8, while the metallic properties of the elements decrease. Thus, metallic properties are more pronounced the fewer electrons there are in the outer level.

Rice. 3. Small and large periods in the periodic table.

Atomic properties such as ionization energy, electron affinity energy, and electronegativity also recur periodically. These quantities are associated with the ability of an atom to give up an electron from an external level (ionization) or to retain someone else’s electron at its external level (electron affinity).. Total ratings received: 146.

Periodic law D.I. Mendeleev:Properties of simple bodies, as well as shapes and properties of compoundsdifferences of elements are periodically dependent onthe values ​​of the atomic weights of elements. (The properties of elements are periodically dependent on the charge of the atoms of their nuclei).

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.

The meaning of the periodic systemWe. 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.

7. 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, as Z increases, 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.

Anyone who went to school remembers that one of the compulsory subjects to study was chemistry. You might like her, or you might not like her - it doesn't matter. And it is likely that much knowledge in this discipline has already been forgotten and is not used in life. However, everyone probably remembers D.I. Mendeleev’s table of chemical elements. For many, it has remained a multi-colored table, where certain letters are written in each square, indicating the names of chemical elements. But here we will not talk about chemistry as such, and describe hundreds of chemical reactions and processes, but we will tell you how the periodic table appeared in the first place - this story will be interesting to any person, and indeed to all those who are hungry for interesting and useful information .

A little background

Back in 1668, the outstanding Irish chemist, physicist and theologian Robert Boyle published a book in which many myths about alchemy were debunked, and in which he discussed the need to search for indecomposable chemical elements. The scientist also gave a list of them, consisting of only 15 elements, but admitted the idea that there may be more elements. This became the starting point not only in the search for new elements, but also in their systematization.

A hundred years later, the French chemist Antoine Lavoisier compiled a new list, which already included 35 elements. 23 of them were later found to be indecomposable. But the search for new elements continued by scientists around the world. And the main role in this process was played by the famous Russian chemist Dmitry Ivanovich Mendeleev - he was the first to put forward the hypothesis that there could be a relationship between the atomic mass of elements and their location in the system.

Thanks to painstaking work and comparison of chemical elements, Mendeleev was able to discover the connection between the elements, in which they can be one, and their properties are not something taken for granted, but represent a periodically repeating phenomenon. As a result, in February 1869, Mendeleev formulated the first periodic law, and already in March his report “Relationship of properties with the atomic weight of elements” was presented to the Russian Chemical Society by the historian of chemistry N. A. Menshutkin. Then, in the same year, Mendeleev’s publication was published in the journal “Zeitschrift fur Chemie” in Germany, and in 1871, another German journal “Annalen der Chemie” published a new extensive publication by the scientist dedicated to his discovery.

Creating the periodic table

By 1869, the main idea had already been formed by Mendeleev, and in a fairly short time, but for a long time he could not formalize it into any orderly system that would clearly display what was what. In one of the conversations with his colleague A.A. Inostrantsev, he even said that he had everything already worked out in his head, but he couldn’t put everything into a table. After this, according to Mendeleev’s biographers, he began painstaking work on his table, which lasted three days without breaks for sleep. They tried all sorts of ways to organize elements into a table, and the work was also complicated by the fact that at that time science did not yet know about all the chemical elements. But, despite this, the table was still created, and the elements were systematized.

The legend of Mendeleev's dream

Many have heard the story that D.I. Mendeleev dreamed about his table. This version was actively disseminated by the aforementioned Mendeleev’s associate A. A. Inostrantsev as a funny story with which he entertained his students. He said that Dmitry Ivanovich went to bed and in a dream clearly saw his table, in which all the chemical elements were arranged in the right order. After this, the students even joked that 40° vodka was discovered in the same way. But there were still real prerequisites for the story with sleep: as already mentioned, Mendeleev worked on the table without sleep or rest, and Inostrantsev once found him tired and exhausted. During the day, Mendeleev decided to take a short rest, and some time later, he woke up abruptly, immediately took a piece of paper and drew a ready-made table on it. But the scientist himself refuted this whole story with the dream, saying: “I’ve been thinking about it, maybe for twenty years, and you think: I was sitting and suddenly... it’s ready.” So the legend of the dream may be very attractive, but the creation of the table was only possible through hard work.

Further work

Between 1869 and 1871, Mendeleev developed the ideas of periodicity toward which the scientific community was inclined. And one of the important stages of this process was the understanding that any element in the system should have, based on the totality of its properties in comparison with the properties of other elements. Based on this, and also relying on the results of research into changes in glass-forming oxides, the chemist was able to make corrections to the values ​​of the atomic masses of some elements, including uranium, indium, beryllium and others.

Mendeleev, of course, wanted to quickly fill the empty cells that remained in the table, and in 1870 he predicted that chemical elements unknown to science would soon be discovered, the atomic masses and properties of which he was able to calculate. The first of these were gallium (discovered in 1875), scandium (discovered in 1879) and germanium (discovered in 1885). Then the forecasts continued to be realized, and eight more new elements were discovered, including: polonium (1898), rhenium (1925), technetium (1937), francium (1939) and astatine (1942-1943). By the way, in 1900, D.I. Mendeleev and the Scottish chemist William Ramsay came to the conclusion that the table should also include elements of group zero - until 1962 they were called inert gases, and after that - noble gases.

Organization of the periodic table

Chemical elements in D.I. Mendeleev’s table are arranged in rows, in accordance with the increase in their mass, and the length of the rows is selected so that the elements in them have similar properties. For example, noble gases such as radon, xenon, krypton, argon, neon and helium are difficult to react with other elements and also have low chemical reactivity, which is why they are located in the far right column. And the elements in the left column (potassium, sodium, lithium, etc.) react well with other elements, and the reactions themselves are explosive. Simply put, within each column, elements have similar properties that vary from one column to the next. All elements up to No. 92 are found in nature, and from No. 93 artificial elements begin, which can only be created in laboratory conditions.

In its original version, the periodic system was understood only as a reflection of the order existing in nature, and there were no explanations as to why everything should be this way. It was only when quantum mechanics appeared that the true meaning of the order of elements in the table became clear.

Lessons in the creative process

Speaking about what lessons of the creative process can be drawn from the entire history of the creation of D. I. Mendeleev’s periodic table, we can cite as an example the ideas of the English researcher in the field of creative thinking Graham Wallace and the French scientist Henri Poincaré. Let's give them briefly.

According to the studies of Poincaré (1908) and Graham Wallace (1926), there are four main stages of creative thinking:

• Preparation– the stage of formulating the main problem and the first attempts to solve it;
• Incubation– a stage during which there is a temporary distraction from the process, but work on finding a solution to the problem is carried out on a subconscious level;
• Insight– the stage at which the intuitive solution is located. Moreover, this solution can be found in a situation that is completely unrelated to the problem;
• Examination– the stage of testing and implementation of a solution, at which this solution is tested and its possible further development.

As we can see, in the process of creating his table, Mendeleev intuitively followed precisely these four stages. How effective this is can be judged by the results, i.e. by the fact that the table was created. And given that its creation was a huge step forward not only for chemical science, but also for all of humanity, the above four stages can be applied both to the implementation of small projects and to the implementation of global plans. The main thing to remember is that not a single discovery, not a single solution to a problem can be found on its own, no matter how much we want to see them in a dream and no matter how much we sleep. In order for something to work out, it doesn’t matter whether it’s creating a table of chemical elements or developing a new marketing plan, you need to have certain knowledge and skills, as well as skillfully use your potential and work hard.

We wish you success in your endeavors and successful implementation of your plans!