PERIODIC TABLE OF MENDELEEV

Building a Periodic Table chemical elements Mendeleev corresponds to the characteristic periods of number theory and orthogonal bases. Complementing Hadamard matrices with matrices of even and odd orders creates a structural basis of nested matrix elements: matrices of the first (Odin), second (Euler), third (Mersenne), fourth (Hadamard), and fifth (Fermat) orders.

It is easy to see that orders of magnitude 4 k Hadamard matrices correspond to inert elements with an atomic mass that is a multiple of four: helium 4, neon 20, argon 40 (39.948), etc., but also the foundations of life and digital technology: carbon 12, oxygen 16, silicon 28, germanium 72.

It seems that with Mersenne matrices of orders 4 k-1, on the contrary, everything active, poisonous, destructive and corrosive is connected. But these are also radioactive elements - sources of energy, and lead 207 (the end product, poisonous salts). Fluorine, of course, is 19. The orders of the Mersenne matrices correspond to a sequence of radioactive elements called the actinium series: uranium 235, plutonium 239 (an isotope that is a more powerful source of atomic energy than uranium), etc. These are also alkali metals lithium 7, sodium 23 and potassium 39.

Gallium - atomic weight 68

Orders 4 k–2 Euler matrices (double Mersenne) corresponds to nitrogen 14 (atmospheric base). Table salt is formed by two "mersenne-like" atoms of sodium 23 and chlorine 35, together this combination is typical, just for Euler matrices. More massive chlorine with a weight of 35.4 is a little short of the Hadamard dimension of 36. Common salt crystals: a cube (! i.e., a meek character, Hadamars) and an octahedron (more defiant, this is undoubtedly Euler).

IN atomic physics transition iron 56 - nickel 59, this is the boundary between the elements that provide energy during the synthesis of a larger nucleus ( H-bomb) and decay (uranium). Order 58 is famous for the fact that for it there are not only analogues of Hadamard matrices in the form of Belevich matrices with zeros on the diagonal, there are also no many weighted matrices for it - the nearest orthogonal W(58,53) has 5 zeros in each column and row (deep gap ).

In the series corresponding to the Fermat matrices and their substitutions of orders 4 k+1, costs 257 fermii by the will of fate. You can't say anything, an exact hit. Here is gold 197. Copper 64 (63.547) and silver 108 (107.868), symbols of electronics, apparently do not reach gold and correspond to more modest Hadamard matrices. Copper, with its atomic weight not far from 63, is chemically active - its green oxides are well known.

Boron crystals under high magnification

FROM golden ratio boron is connected - the atomic mass among all other elements is closest to 10 (more precisely, 10.8, the proximity of the atomic weight to odd numbers also affects). Boron is a fairly complex element. Bohr plays a confusing role in the history of life itself. The framework structure in its structures is much more complicated than in diamond. unique type chemical bond, which allows boron to absorb any impurity, is very poorly understood, although for research related to it, a large number of scientists have already received Nobel Prizes. The shape of the boron crystal is an icosahedron, five triangles form a vertex.

Platinum Mystery. The fifth element is, without a doubt, noble metals such as gold. Suspension over Hadamard dimension 4 k, for 1 large.

The stable isotope uranium 238

Recall, however, that Fermat numbers are rare (the closest is 257). Native gold crystals have a shape close to a cube, but the pentagram also sparkles. Its closest neighbor, platinum, a noble metal, is less than 4 times less atomic weight away from gold 197. Platinum has an atomic weight not 193, but somewhat increased, 194 (the order of the Euler matrices). A trifle, but it brings her into the camp of a few more aggressive elements. It is worth remembering, due to the fact that with its inertness (it dissolves, perhaps, in aqua regia), platinum is used as an active catalyst chemical processes.

Sponge platinum at room temperature ignites hydrogen. The nature of platinum is not at all peaceful, iridium 192 behaves more quietly (a mixture of isotopes 191 and 193). It is more like copper, but with the weight and character of gold.

Between neon 20 and sodium 23 there is no element with an atomic weight of 22. Of course, atomic weights are an integral characteristic. But among isotopes, in turn, there is also a curious correlation of properties with the properties of numbers and the corresponding matrices of orthogonal bases. As nuclear fuel The most widely used isotope is uranium 235 (Mersenne matrix order), in which a self-sustaining chain nuclear reaction. In nature, this element occurs in the stable form uranium 238 (the order of the Euler matrices). There is no element with an atomic weight of 13. As for chaos, the limited number of stable elements of the periodic table and the difficulty of finding high-order level matrices due to the barrier seen in thirteenth-order matrices correlate.

Isotopes of chemical elements, island of stability

He drew on the work of Robert Boyle and Antoine Lavouzier. The first scientist advocated the search for indecomposable chemical elements. 15 of those Boyle listed back in 1668.

Lavuzier added 13 more to them, but a century later. The search dragged on because there was no coherent theory of the connection between the elements. Finally, Dmitry Mendeleev entered the "game". He decided that there is a connection between the atomic mass of substances and their place in the system.

This theory allowed the scientist to discover dozens of elements without discovering them in practice, but in nature. This was placed on the shoulders of posterity. But now it's not about them. Let's dedicate the article to the great Russian scientist and his table.

The history of the creation of the periodic table

Mendeleev table began with the book "Relationship of properties with the atomic weight of the elements." The work was issued in the 1870s. At the same time, the Russian scientist spoke to the chemical society of the country and sent the first version of the table to colleagues from abroad.

Before Mendeleev, 63 elements were discovered by various scientists. Our compatriot began by comparing their properties. First of all, he worked with potassium and chlorine. Then, he took up the group of metals of the alkaline group.

The chemist got a special table and element cards to lay them out like solitaire, looking for the right matches and combinations. As a result, an insight came: - the properties of the components depend on the mass of their atoms. So, elements of the periodic table lined up in ranks.

The discovery of the maestro of chemistry was the decision to leave voids in these ranks. The periodicity of the difference between atomic masses led the scientist to assume that not all elements are known to mankind yet. The gaps in weight between some of the "neighbors" were too large.

That's why, periodic table of Mendeleev became like chess field, with an abundance of "white" cells. Time has shown that they really were waiting for their "guests". They, for example, became inert gases. Helium, neon, argon, krypton, radioact and xenon were discovered only in the 30s of the 20th century.

Now about myths. It is widely believed that chemical table Mendeleev appeared to him in a dream. These are the intrigues of university teachers, more precisely, one of them - Alexander Inostrantsev. This is a Russian geologist who lectured at the St. Petersburg University of Mining.

Inostrantsev knew Mendeleev and visited him. Once, exhausted by the search, Dmitry fell asleep right in front of Alexander. He waited until the chemist wakes up and saw how Mendeleev grabs a piece of paper and writes down the final version of the table.

In fact, the scientist simply did not have time to do this before Morpheus captured him. However, Inostrantsev wanted to amuse his students. Based on what he saw, the geologist came up with a bike, which grateful listeners quickly spread to the masses.

Features of the periodic table

Since the first version in 1969 ordinal periodic table improved many times. So, with the discovery of noble gases in the 1930s, it was possible to derive a new dependence of the elements - on their serial numbers, and not on the mass, as the author of the system stated.

The concept of "atomic weight" was replaced by "atomic number". It was possible to study the number of protons in the nuclei of atoms. This figure is serial number element.

20th century scientists have studied and electronic structure atoms. It also affects the periodicity of elements and is reflected in later editions. periodic tables. A photo The list shows that the substances in it are arranged as the atomic weight increases.

The fundamental principle was not changed. Mass increases from left to right. At the same time, the table is not single, but divided into 7 periods. Hence the name of the list. Period is a horizontal row. Its beginning is typical metals, the end is elements with non-metallic properties. The decline is gradual.

There are big and small periods. The first ones are at the beginning of the table, there are 3 of them. It opens a list with a period of 2 elements. Following are two columns, in which there are 8 items. The remaining 4 periods are large. The 6th is the longest, it has 32 elements. In the 4th and 5th there are 18 of them, and in the 7th - 24.

Can be counted how many elements in the table Mendeleev. There are 112 titles in total. Names. There are 118 cells, but there are variations of the list with 126 fields. There are still empty cells for undiscovered elements that do not have names.

Not all periods fit on one line. Large periods consist of 2 rows. The amount of metals in them outweighs. Therefore, the bottom lines are completely devoted to them. A gradual decrease from metals to inert substances is observed in the upper rows.

Pictures of periodic table divided vertically. This groups in the periodic table, there are 8 of them. Elements similar in chemical properties are arranged vertically. They are divided into main and secondary subgroups. The latter begin only from the 4th period. The main subgroups also include elements of small periods.

The essence of the periodic table

Names of elements in the periodic table is 112 positions. The essence of their arrangement in a single list is the systematization of primary elements. They began to fight over this even in ancient times.

Aristotle was one of the first to understand what everything that exists was made of. He took as a basis the properties of substances - cold and heat. Empidocles singled out 4 fundamental principles according to the elements: water, earth, fire and air.

Metals in the periodic table, like other elements, are the very fundamental principles, but from a modern point of view. The Russian chemist managed to discover most of the components of our world and to suggest the existence of still unknown primary elements.

Turns out that pronunciation of the periodic table- voicing a certain model of our reality, decomposing it into components. However, learning them is not easy. Let's try to make the task easier by describing a couple of effective methods.

How to learn the periodic table

Let's start with modern method. Computer scientists have developed a number of flash games that help memorize Mendeleev's list. Project participants are offered to find elements by different options, for example, name, atomic mass, letter designation.

The player has the right to choose the field of activity - only part of the table, or all of it. In our will, also, exclude the names of elements, other parameters. This complicates the search. For the advanced, a timer is also provided, that is, training is carried out at speed.

Game conditions make learning element numbers in the periodic table not boring, but entertaining. Excitement wakes up, and it becomes easier to systematize knowledge in the head. Those who do not accept computer flash projects offer more traditional way learning the list.

It is divided into 8 groups, or 18 (according to the 1989 edition). For ease of remembering, it is better to create several separate tables, rather than working on a whole version. Help and visual images matched to each of the elements. Rely on your own associations.

So, iron in the brain can be correlated, for example, with a nail, and mercury with a thermometer. The name of the element is unfamiliar? We use the method of suggestive associations. , for example, we will compose from the beginnings of the words "taffy" and "speaker".

Characteristics of the periodic table don't study in one sitting. Lessons are recommended for 10-20 minutes a day. It is recommended to start by remembering only the basic characteristics: the name of the element, its designation, atomic mass and serial number.

Schoolchildren prefer to hang the periodic table above the desktop, or on the wall, which is often looked at. The method is good for people with a predominance of visual memory. Data from the list is involuntarily remembered even without cramming.

This is also taken into account by teachers. As a rule, they do not force you to memorize the list, they allow you to look at it even on the control ones. Constantly looking at the table is tantamount to the effect of printing on the wall, or writing cheat sheets before exams.

Starting the study, let us recall that Mendeleev did not immediately remember his list. Once, when the scientist was asked how he opened the table, the answer was: “I’ve been thinking about it for maybe 20 years, but you think: I sat and, suddenly, it’s ready.” Periodic system- painstaking work that cannot be mastered in a short time.

Science does not tolerate haste, because it leads to delusions and annoying mistakes. So, at the same time as Mendeleev, the table was compiled by Lothar Meyer. However, the German did not finish the list a bit and was not convincing in proving his point of view. Therefore, the public recognized the work of the Russian scientist, and not his fellow chemist from Germany.

The periodic table is one of greatest discoveries humanity, which made it possible to streamline knowledge about the world around us and discover new chemical elements. It is necessary for schoolchildren, as well as for everyone who is interested in chemistry. Besides, this scheme is indispensable in other fields of science.

This diagram contains all known to man elements, and they are grouped according to atomic mass and serial number. These characteristics affect the properties of the elements. In total, there are 8 groups in the short version of the table, the elements included in one group have very similar properties. The first group contains hydrogen, lithium, potassium, copper, the Latin pronunciation in Russian of which is cuprum. And also argentum - silver, cesium, gold - aurum and francium. The second group contains beryllium, magnesium, calcium, zinc, followed by strontium, cadmium, barium, and the group ends with mercury and radium.

The third group includes boron, aluminum, scandium, gallium, then yttrium, indium, lanthanum, and the group ends with thallium and actinium. The fourth group begins with carbon, silicon, titanium, continues with germanium, zirconium, tin, and ends with hafnium, lead, and rutherfordium. In the fifth group there are elements such as nitrogen, phosphorus, vanadium, arsenic, niobium, antimony are located below, then bismuth tantalum comes and completes the dubnium group. The sixth begins with oxygen, followed by sulfur, chromium, selenium, then molybdenum, tellurium, then tungsten, polonium and seaborgium.

In the seventh group, the first element is fluorine, followed by chlorine, manganese, bromine, technetium, followed by iodine, then rhenium, astatine and borium. The last group is the most numerous. It includes gases such as helium, neon, argon, krypton, xenon and radon. This group also includes the metals iron, cobalt, nickel, rhodium, palladium, ruthenium, osmium, iridium, platinum. Next come hannium and meitnerium. Separately located elements that form the actinide series and the lanthanide series. They have similar properties to lanthanum and actinium.

This scheme includes all types of elements, which are divided into 2 large groups – metals and non-metals with different properties. How to determine whether an element belongs to a particular group, a conditional line will help, which must be drawn from boron to astatine. It should be remembered that such a line can only be drawn in full version tables. All elements that are above this line and are located in the main subgroups are considered non-metals. And which are lower, in the main subgroups - metals. Also, metals are substances that are in side subgroups. There are special pictures and photos on which you can get acquainted with the position of these elements in detail. It is worth noting that those elements that are on this line exhibit the same properties of both metals and non-metals.

A separate list is also made up of amphoteric elements, which have dual properties and can form 2 types of compounds as a result of reactions. At the same time, they manifest equally both basic and acid properties . The predominance of certain properties depends on the reaction conditions and the substances with which the amphoteric element reacts.

It should be noted that this scheme in the traditional execution of good quality is color. Wherein different colors for ease of orientation are marked main and secondary subgroups. And also elements are grouped depending on the similarity of their properties.
However, at present, along with the color scheme, the black-and-white periodic table of Mendeleev is very common. This type is used for black and white printing. Despite the apparent complexity, working with it is just as convenient, given some of the nuances. So, in this case, it is possible to distinguish the main subgroup from the secondary one by differences in shades that are clearly visible. In addition, in the color version, elements with the presence of electrons on different layers are indicated different colors.
It is worth noting that in a single-color design it is not very difficult to navigate the scheme. For this, the information indicated in each individual cell of the element will be enough.

The exam today is the main type of test at the end of school, which means that preparation for it must be given Special attention. Therefore, when choosing final exam in chemistry, you need to pay attention to the materials that can help in its delivery. As a rule, schoolchildren are allowed to use some tables during the exam, in particular, the periodic table in good quality. Therefore, in order for it to bring only benefit in tests, attention should be paid in advance to its structure and the study of the properties of the elements, as well as their sequence. You also need to learn use the black and white version of the table so that you don't face any difficulties in the exam.

In addition to the main table characterizing the properties of elements and their dependence on atomic mass, there are other schemes that can help in the study of chemistry. For example, there are tables of solubility and electronegativity of substances. The first one can determine how soluble a particular compound is in water at ordinary temperature. In this case, anions are located horizontally - negatively charged ions, and cations, that is, positively charged ions, are located vertically. To find out degree of solubility of one or another compound, it is necessary to find its components in the table. And at the place of their intersection there will be the necessary designation.

If it is the letter "r", then the substance is completely soluble in water under normal conditions. In the presence of the letter "m" - the substance is slightly soluble, and in the presence of the letter "n" - it almost does not dissolve. If there is a “+” sign, the compound does not form a precipitate and reacts with the solvent without residue. If a "-" sign is present, it means that such a substance does not exist. Sometimes you can also see the sign “?” in the table, then this means that the degree of solubility of this compound is not known for certain. Electronegativity of the elements can vary from 1 to 8, there is also a special table to determine this parameter.

One more useful table is the activity series of metals. All metals are located in it by increasing the degree of electrochemical potential. A series of stress metals begins with lithium, ends with gold. It is believed that the further to the left a metal occupies in this row, the more active it is in chemical reactions. In this way, the most active metal Lithium is considered to be an alkaline metal. Hydrogen is also present at the end of the list of elements. It is believed that the metals that are located after it are practically inactive. Among them are elements such as copper, mercury, silver, platinum and gold.

Periodic table pictures in good quality

This scheme is one of the greatest achievements in the field of chemistry. Wherein There are many types of this table. – short version, long, and also extra long. The most common is a short table, it is also common long version schemes. It is worth noting that the short version of the scheme is not currently recommended by IUPAC for use.
Total was more than a hundred types of tables have been developed, which differ in presentation, shape, and graphical representation. They are used in different areas science, or not applied at all. Currently, new circuit configurations continue to be developed by researchers. As the main option, either a short or a long circuit in excellent quality is used.

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 are periodically repeated.

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

At the beginning of each period (with the exception of the first) there is an element with pronounced metallic properties (alkali metal).

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

As the atomic number of the element increases, equal to the value of the positive charge of the nucleus of its atom, the metallic properties gradually weaken and the 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 each, in IV and V - 18 elements each, in VI - 32 and in VII (incomplete 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 (excluding the VII period) consists of two horizontal rows - even (upper) and odd (lower). In even rows long periods there are only metals. The properties of the elements in these rows change slightly with increasing serial number. The properties of elements in odd series of large periods change. In period VI, lanthanum is followed by 14 elements that are very similar in chemical properties. These elements, called lanthanides, are listed separately under the main table. Actinides, the elements following actinium, are similarly presented in the table.

The table has nine vertical groups. The group number, with rare exceptions, is equal to the highest positive valence of the elements of this group. Each group, excluding zero and eighth, is divided into subgroups. - main (located to the right) and side. In the main subgroups, with an increase in the serial number, the metallic properties of the elements increase and the non-metallic properties of the elements 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 system.

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

The periodic system 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 the original wording periodic law D. I. Mendeleev argued: the properties of chemical elements, as well as the forms and properties of their compounds, are in a periodic dependence on the magnitude of the atomic weights of the elements. Later, with the development of the theory of the structure of the atom, it was shown that more accurate characterization of each element is not the atomic weight (see), but the value of the positive charge of the nucleus of the atom of the element, equal to the ordinal (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 an 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 in a periodic dependence on the positive charge of the nuclei of their atoms. This means that in a continuous series of elements arranged in ascending order of the positive charges of the nuclei of their atoms, elements with similar properties will be periodically repeated.

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

At the beginning of each period (with the exception of 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 of the elements increase. The penultimate element in each period is an element with pronounced non-metallic properties (halogen), and the last is an inert gas. Period I consists of two elements, the role of an alkali metal and a halogen is simultaneously performed by hydrogen. II and III periods include 8 elements each, called Mendeleev typical. IV and V periods have 18 elements each, VI-32. VII period is not yet completed and is replenished with artificially created elements; there are currently 17 elements in this period. I, II and III periods are called small, each of them consists of one horizontal row, IV-VII - large: they (with the exception of VII) include two horizontal rows - even (upper) and odd (lower). In even rows of large periods, only metals are found, and the change in the properties of the 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 an even number of the VI period after lanthanum follows 14 elements [called lanthanides (see), lanthanides, rare earth elements], similar in chemical properties to lanthanum and to each other. Their list is given separately under the table.

Separately, the elements following the actinium-actinides (actinides) are written out and given under the table.

There are nine vertical groups in the periodic table of chemical elements. The group number is equal to the highest positive valency (see) of the elements of this group. The exceptions are fluorine (it happens only negatively monovalent) and bromine (it does not happen heptavalent); in addition, copper, silver, gold can show a valency greater than +1 (Cu-1 and 2, Ag and Au-1 and 3), and from the elements Group VIII Only osmium and ruthenium have a +8 valence. Each group, with the exception of the eighth and zero, is divided into two subgroups: the main (located to the right) and the secondary. The main subgroups include typical elements and elements of large periods, the secondary - only elements of large periods and, moreover, metals.

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

Some groups of elements have special names. So, the elements of the main subgroups of group I are called alkali metals, group II - alkaline earth metals, VII group- halogens, elements located behind uranium - transuranium. Elements that are part of organisms, take part in metabolic processes and have a pronounced biological role are called biogenic elements. All of them occupy the upper part of the table of D. I. Mendeleev. This is 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 in light blue. Biogenic elements, which are very few in the body (from 10 -3 to 10 -14%), are called microelements (see). In the cells of the periodic system, stained in yellow, trace elements are placed, the vital importance of which for humans has been proven.

According to the theory of the structure of atoms (see Atom), the chemical properties of elements depend mainly on the number of electrons in the outer electron shell. Periodic change in the properties of elements with an increase in positive charge atomic nuclei due to the periodic repetition of the structure of the outer electron shell (energy level) of 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 the 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 the zero group are chemically inert).

In large periods in even rows, with an increase in the positive charge of the nuclei, 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 odd series of long periods, with an increase in the charge of the nuclei, the outer shell is filled with electrons (from 1 to 8) and the properties of the elements change in the same way as for typical elements.

The number of electron shells in an atom is equal to the period number. The atoms of the elements of the main subgroups have a number of electrons on their outer shells equal to the group number. The atoms of the elements of the secondary subgroups contain one or two electrons on the 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 electrons are valence outer shells, but also the penultimate ones. The number and structure of electron shells are indicated in the attached periodic table of chemical elements.

The periodic law of D. I. Mendeleev and the system based on it have exclusively great importance in science and practice. The periodic law and the system were the basis for the discovery of new chemical elements, exact definition their atomic weights, the development of the doctrine of the structure of atoms, the establishment of geochemical laws for the distribution of elements in earth's crust and the development of modern ideas about living matter, the composition of which and the laws associated with it are in accordance with the periodic system. Biological activity elements and their content in the body are also largely determined by the place they occupy in the periodic system of Mendeleev. So, 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 vivid expression of the most general dialectical laws of the development of nature.

Instruction

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

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

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

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

The electrons are in different distance from the nucleus, forming electronic levels. To determine the number of electronic (or energy) levels, you need to look at the number of the period in which the element is located. For example, 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 valence. For example, the elements of the first group of the main subgroup (lithium, sodium, potassium, etc.) have a valency of 1. Accordingly, the elements of the second group (beryllium, calcium, etc.) will have a valency of 2.

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

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

Useful advice

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

The discovery of the periodic law and the 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 generalized and systematized an extensive material of knowledge about the properties of elements.

Instruction

In the 19th century there were no ideas about the structure of the atom. Discovery of D.I. Mendeleev was only a generalization of experimental facts, but their physical meaning long time remained unclear. When the first data on the structure of the nucleus and the distribution of electrons in atoms appeared, it was to look at the law and the 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 revolving around the nucleus. The number of protons is thus equal to the number of electrons, and this indicates that under normal conditions the atom is electrically .

The division into seven periods is based on the number energy levels 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, new period.

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, inert gases have 2 electrons, in the subsequent ones - 8. It is precisely because of the similar structure of the electron shells that groups of elements have similar physico-.

In the table D.I. Mendeleev there are 8 main subgroups. Their number is due to the maximum possible number of electrons at the energy level.

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

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

A clearly traced periodicity in the arrangement of elements in the table D.I. Mendeleev is rationally explained by the consistent nature of the filling of energy levels by 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 in the study of the complex structure of the atom.

In the 19th century, atomic mass was thought to be main characteristic element, so it was used to classify substances. Now atoms are defined and identified by the magnitude of the charge of their nucleus (number and serial number in the periodic table). However, the atomic mass of the 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 the atomic mass, a periodic change in the properties of elements and their compounds is observed. These are metallicity and non-metallicity of atoms, atomic radius, ionization potential, electron affinity, electronegativity, oxidation states, compounds (boiling, melting points, density), their basicity, amphotericity or acidity.

How many elements are in the modern periodic table

Periodic table graphically expresses the law discovered by him. The modern periodic system contains 112 chemical elements (the latter are Meitnerius, Darmstadtius, Roentgenium and Copernicius). According to the latest data, the following 8 elements (up to 120 inclusive) have also been discovered, but not all of them have received their names, and these elements are still few in any printed publications.

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

How the periodic system is built

The structure of the periodic system 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 ones (fourth, fifth, sixth) consist 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 taken out in lower part tables on a separate line. The same applies to actinides located after actinium (with number 89) and largely repeating its properties.

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

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

Advice 4: Selenium as a chemical element of the periodic table

The chemical element selenium belongs to group VI of the periodic system of Mendeleev, it is a chalcogen. Natural selenium consists of six stable isotopes. Also known 16 radioactive isotopes Selene.

Instruction

Selenium is considered a very rare and dispersed 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, bismuthine and other sulfides. It is mined from lead, copper, nickel and other ores, in which it is found in a dispersed state.

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

Selenium can exist in various allotropic modifications: amorphous (glassy, ​​powdered and colloidal selenium), as well as crystalline. When selenium is reduced from a solution of selenous acid or by rapid cooling of its vapor, red powdered and colloidal selenium is obtained.

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

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

Selenium is stable in air, it is not affected by: oxygen, water, dilute sulfuric and hydrochloric acid, however, it dissolves well in nitric acid. Interacting with metals, selenium forms selenides. Many are known complex compounds selenium, they are all poisonous.

Selenium is obtained from waste paper or production, by electrolytic refining of copper. In slimes, this element is present together 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 rectifier semiconductor diodes and other converter equipment. In metallurgy, it is used to give steel a fine-grained structure, and also improve it. mechanical properties. IN chemical industry selenium is used as a catalyst.

Sources:

• HimiK.ru, Selenium

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

Instruction

FROM Latin"" translates as "lime" or "soft stone", and he owes his discovery to the Englishman Humphry Davy, who in 1808 was able to isolate calcium by the electrolytic method. The scientist then took a mixture of wet slaked lime, “seasoned” with mercury oxide, and subjected it to an electrolysis process on a platinum plate, which appears in the experiment as an anode. The cathode was a wire, which the chemist immersed in liquid mercury. It is also interesting that such calcium compounds as limestone, marble and gypsum, as well as lime, were known to mankind many centuries before the Davy experiment, during which scientists considered some of them to be simple and independent bodies. Only in 1789 did the Frenchman Lavoisier publish a work in which he suggested that lime, silica, barite and alumina are complex substances.

Calcium has a high degree chemical activity, due to which pure form practically does not occur in nature. But scientists have calculated that this element accounts for about 3.38% of the total mass of the entire earth's crust, which makes calcium the fifth most abundant after oxygen, silicon, aluminum and iron. There is this element in sea ​​water- about 400 mg per liter. Calcium is also included in the composition of silicates of various rocks(for example, granite and gneiss). There is a lot of it in feldspar, chalk and limestone, consisting of the mineral calcite with the formula CaCO3. The crystalline form of calcium is marble. In total, by migration of this element in the earth's crust, it forms 385 minerals.

The physical properties of calcium include its ability to exhibit valuable semiconductor 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 informed metallic state and ability to manifest superconducting properties. Calcium easily interacts with oxygen, air moisture and carbon dioxide, which is why in laboratories for work this chemical element is stored in tightly closed 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 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 Dmitri Mendeleev's discovery was a periodic, rather than a monotonous change chemical properties elements with increasing atomic mass. The final unification of the theory into the periodic law took place in 1871.

Legends about Mendeleev

The most common legend is the opening of the periodic table in a dream. The scientist himself repeatedly ridiculed this myth, claiming that he had been inventing the table for many years. According to another legend, Dmitry Mendeleev vodka - it appeared after the defense dissertations"A Discourse on the Combination of Alcohol with Water".

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

According to rumors, a separate reason for jokes was Dmitri Mendeleev's passion for weaving suitcases, which the scientist was engaged in while living in Simferopol. In the future, he made cardboard for the needs of his laboratory, for which he was caustically called a suitcase master.

Periodic table, except for the ordering of chemical elements in 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.