Periodic system of chemical elements D.I. Imeteleev

In fact, the German physicist Johann Wolfgang Dobereer noted the characteristics of the grouping of the elements back in 1817. In those days, chemists have not yet fully understood the nature of atoms described by John Dalton in 1808. In his "new chemical philosophy", Dalton explained the chemical reactions, assuming that each elementary substance consists of a certain type atom.

Dalton suggested that chemical reactions produced new substances when atoms are separated or connected. He believed that any element consists exclusively of one type of atom, which differs from others by weight. Oxygen atoms weighed eight times more than hydrogen atoms. Dalton believed that carbon atoms are six times heavier than hydrogen. When the elements are combined to create new substances, the amount of reacting substances can be calculated taking into account these atomic scales.

Dalton became mistaken about some mass - oxygen in reality 16 times heavier than hydrogen, and carbon is 12 times heavier than hydrogen. But his theory made an idea about atoms useful, inspiring the revolution in chemistry. The exact measurement of the atomic mass was the main problem of chemists for the next decades.

Reflecting on these scales, Dobereer noted that certain sets of three elements (he called them triads) show an interesting connection. Bromine, for example, had a nuclear mass somewhere between the masses of chlorine and iodine, and all these three elements demonstrated similar chemical behavior. Lithium, sodium and potassium were also triad.

Other chemists have noticed links between atomic masses and, but only in the 1860s, atomic masses have become well enough and measured to make a deeper understanding. English Chemist John Newlands noticed that the location of the known elements in order to increase the atomic mass led to the repetition of the chemical properties of each eighth element. He called this model "Oktall Law" in Article 1865. But the Newlands model did not very well after the first two octave, which made critics suggest it to arrange elements in alphabetical order. And as Mendeleev soon understood, the ratio of the properties of elements and atomic masses was slightly more complex.

Organization of chemical elements

Mendeleev was born in Tobolsk, in Siberia, in 1834 and was a seventeenth child from his parents. He lived a bright life, pursuing different interests and traveling on the road to outstanding people. During the receipt of higher education at the Pedagogical Institute in St. Petersburg, he almost died of severe illness. After graduation, he taught in secondary schools (it was necessary to receive salary at the institute), passing by mathematics and natural sciences to obtain a master's degree.

He then worked as a teacher and lecturer (and wrote scientific work), until he received a scholarship for an expanded tour of the research in the best chemical laboratories in Europe.

Returning to St. Petersburg, he was without work, so he wrote an excellent guide to in the hope of winning a major money prize. In 1862, this brought him a Demidov Prize. He also worked as an editor, translator and consultant in various chemical spheres. In 1865, he returned to research, received a doctor of science and became a professor at the University of St. Petersburg.

Soon after that, Mendeleev began teaching inorganic chemistry. Preparing to master this new (for him) the field, he remained dissatisfied with accessible textbooks. Therefore, I decided to write your own. The organization of the text required the organization of elements, so the issue of their best location was incessantly in his mind.

By the beginning of 1869, Mendeleev achieved sufficient progress to understand that some groups of such elements demonstrated a regular increase in atomic masses; Other elements with approximately the same atomic masses had similar properties. It turned out that the streamlining of elements by their atomic weight was the key to their classification.

Periodic table D. Meneleeva.

According to his own words, Mendeleev, he struduered his thinking, writing each of the 63 elements known to the elements on a separate card. Then, through a kind of game in Chemical Solitaire, he found the pattern that he was looking for. Posing cards in vertical columns with atomic masses from low to higher, it has placed items with similar properties in each horizontal range. Periodic table of Mendeleev was born. He sketched the draft version on March 1, sent it to print and included in his textbook, which should have been published soon. He also quickly prepared work for the presentation by Russian chemical society.

"Elements, ordered in the sizes of their atomic masses, show clear periodic properties," wrote Mendeleev in his work. "All the comparisons that I spent, led me to the conclusion that the size of the atomic mass determines the nature of the elements."

Meanwhile, the German chemist Lothar Meyer also worked on the organization of elements. He prepared a table similar to Mendeleevskaya, perhaps even earlier than Mendeleev. But Mendeleev issued his first.

Nevertheless, much more important than victory over Meyer was how Mendeleev used its table to do about unopened elements. In preparation, his Mendeleev table noted that some cards lacked. He had to leave empty places so that famous elements could align correctly. After his life, three empty places were filled with previously unknown elements: Gallium, Scandium and Germany.

Mendeleev not only predicted the existence of these elements, but also correctly described their properties in detail. Gallium, for example, opened in 1875, had a nuclear mass of 69.9 and a density of six times higher than water. Mendeleev predicted this element (he called it ekaluminum), only on this density and atomic mass 68. Its predictions for Ecakremia were close to Germany (open in 1886) in atomic mass (72 predicted, 72.3 in fact) and density. It also faithfully predicted the density of germanium compounds with oxygen and chlorine.

The Mendeleev table became a prophetic. It seemed that at the end of this game, this rolls will reveal from elements. At the same time, Mendeleev himself was a master in the use of his own table.

Successful predictions of Mendeleev brought him the legendary status of a chemical magic masters. But today historians argue about whether the opening of the predicted elements has consolidated the adoption of its periodic law. The adoption of the law could be more connected with its ability to explain the established chemical connections. In any case, the prognostic accuracy of Mendeleev, of course, attracted attention to the advantages of its table.

By 1890, the chemicals widely recognized his law as a milestone in chemical knowledge. In 1900, the future Nobel laureate in Chemistry William Ramsey called it "the greatest generalization that ever was conducted in chemistry." And Mendeleev did it, without understanding how.

Mathematical Card.

In many cases, in the history of science, great predictions based on new equations turned out to be true. Somehow mathematics reveals some natural secrets before the experimenters detect them. One example is antimatterium, the other is the expansion of the universe. In the case of Mendeleev, the predictions of new elements arose without any creative mathematics. But in fact, Mendeleev opened a deep mathematical map of nature, since its table reflected the value, mathematical rules controlling atomic architecture.

In his book, Mendeleev noted that "the inner differences of matter that the atoms make up" may be responsible for periodically repetitive properties of elements. But he did not adhere to this line of thinking. In fact, for many years he reflected on how important an atomic theory is important for its table.

But others were able to read the inner message of the table. In 1888, the German chemist Johannes Volienin declared that the frequency of the properties of elements ordered by mass indicates that atoms consist of regular groups of smaller particles. Thus, in a sense, the Mendeleev table really foresaw (and provided evidence) the complex internal structure of atoms, while no one had the slightest idea of \u200b\u200bhow an atom actually looked like or whether he had any internal structure at all.

By the time of the death of Mendeleev in 1907, scientists knew that atoms were divided into parts: plus some positively charged component that makes atoms electrically neutral. The key to how these parts are built up, was the discovery of 1911, when the physicist Ernest Rutherford, working in the University of Manchester in England, discovered the atomic core. Shortly after that, Henry Cosli, who worked with Rutherford, demonstrated that the number of positive charge in the core (the number of protons that it contains, or its "atomic number") defines the correct order of elements in the periodic table.

Henry Cosli.

The atomic mass was closely connected with the atomic number of Coslos - it is quite closely that the ordering of elements by weight only in several places differ from ordering. Mendeleev insisted that these masses were wrong and needed a re-measurement, and in some cases it turned out to be right. There are several discrepancies left, but the atomic number of Molds perfectly legally in the table.

At about the same time, the Danish physicist Nils Bor realized that the quantum theory determines the location of the electrons surrounding the kernel, and that the farthest electrons determine the chemical properties of the element.

Such arrangements of external electrons will be periodically repeated, explaining the patterns that originally revealed the Mendeleev table. Bohr created its own version of the table in 1922, based on the experimental measurements of electron energies (along with some prompts from the periodic law).

The Bohr table added elements opened since 1869, but it was the same periodic order, open Mendeleev. Having not the slightest idea of \u200b\u200bO, Mendeleev created a table reflecting the atomic architecture that quantum physics dictated.

The new table boron did not become the first nor the latest version of the initial design of Mendeleev. Hundreds of versions of the periodic table have since been developed and published. Modern form - in horizontal design, unlike the initial vertical version of Mendeleev, became widely popular only after World War II, largely due to the work of the American Chemist Glenn Siforg.

Sitborg and his colleagues created several new elements synthetically, with atomic numbers after uranium, the last natural element in the table. Sitobor saw that these elements, transuranov (plus three elements preceding uranium), demanded a new line in a table that Mendeleev did not foresee. The sibling table added a string for those elements under a similar number of rare earth elements, which also did not have place in the table.

The contribution of Sitoriga to Chemistry brought him the honor to name its own element - Single numbers 106. This is one of several elements called in honor of famous scientists. And in this list, of course, there is an element 101, open by Siborg and his colleagues in 1955 and called Mendelevia - in honor of the chemist, who before all the others earned a place in the periodic table.

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The Mendeleev table is one of the greatest discoveries of mankind, which allowed to streamline the knowledge of the environment and open new chemical elements. It is necessary for schoolchildren, as well as for anyone who is interested in chemistry. In addition, this scheme is indispensable in other areas of science.

This scheme contains all elements known to humans, and they are grouped depending on atomic mass and sequence number. These characteristics affect the properties of elements. In total, there are 8 groups in a short version of the table, elements included in one group have very similar properties. The first group contains hydrogen, lithium, potassium, copper, Latin pronunciation in Russian which can be kept. As well as the Argentum - silver, cesium, gold - Aurum and France. In the second group, beryllium, magnesium, calcium, zinc are located, the strontium, cadmium, barium are coming behind them, ends with mercury and radium.

The third group includes Bor, aluminum, scandium, gallium, then they follow the yttrium, indium, lantant, the group is completed with Tallium and Activity. The fourth group begins with carbon, silicon, titanium, continues Germany, zirconium, tin and ends with hafnia, lead and rootford. In the fifth group there are elements such as nitrogen, phosphorus, vanadium, arsenic, niobium, antimony are located below, then Tantalt Bismuth come and completes the Dubna group. The sixth begins with oxygen, followed by sulfur, chrome, selenium, then follow Molybdenum, tellurium, then tungsten, polonium and sibrie.

In the seventh group, the first element is Fluorous, then the chlorine, manganese, bromine, technetium, is the iodine, then rhenium, Astat and Bory. The last group is numerous itself. It includes such gases as helium, Neon, Argon, Crypton, Xenon and Radon. Also, this group includes metal metal, cobalt, nickel, rhodium, palladium, ruthenium, osmium, iridium, platinum. Next are Hannie and Metery. Separately arranged elements that form a number of actinides and a number of lanthanides. They have similar properties with Lantan and Activity.

This scheme includes all types of elements that are divided into 2 large groups - metals and nonmetallaWith different properties. How to determine the belonging of the element to a particular group, the conditional line will help to spend from Bora to Astanat. It should be remembered that such a line can only be carried out in the full version of the table. All elements that are above this line are located in the main subgroups are considered non-metals. And which are lower, in the main subgroups - metals. Also metals are substances in side subgroups. There are special pictures and photos on which you can familiarize yourself with the position of these elements. It is worth noting that those elements that are on this line exhibit equally properties and metals and non-metals.

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

It is worth noting that this scheme in the traditional performance of good quality is color. In this case, different colors for the convenience of orientation are designated the main and side subgroups. As well as the elements are grouped depending on the similarity of their properties.
However, at present, along with the color scheme, the periodic table of Mendeleev black and white is very common. This type is used for black and white printing. Despite the seeming difficulty, it is also convenient to work with it if you consider some nuances. So, to distinguish the main subgroup from the side in this case, in charge of the shades, which are well noticeable. In addition, in the color version, elements with the presence of electrons on different layers are designated different colors.
It is worth noting that in one-color execution, it is not very difficult to navigate according to the scheme. To do this, there will be enough information specified in each individual element cell.

The exam today is the main type of test at the end of the school, which means that special attention needs to be prepared. Therefore, when choosing final exam in chemistryIt is necessary to pay attention to materials that can help in his surrender. As a rule, schoolchildren on the exam are allowed to use some tables, in particular, the Mendeleev table in good quality. Therefore, so that it brings on tests only the benefit should pay attention to its structure and the study of the properties of elements, as well as their sequences. Need to learn as well use the black and white version of the tableSo that on the exam does not encounter some difficulties.

In addition to the main table, which characterizes the properties of the elements and their dependence on the atomic mass, there are other schemes that can assist in the study of chemistry. For example, exist solubility and Electricity Tables Substances. On the first one can determine how soluble or another connection in water at normal temperature. At the same time, the horizontals are located anions - negatively charged ions, and vertically - cations, that is, positively charged ions. To learn degree of solubility Therefore, or other connection, it is necessary to find its components on the table. And on the place of their intersection will be the necessary designation.

If it is the letter "P", the substance is completely soluble in water under normal conditions. If there is a letter "M" - a substance is a malstutable, and if there is a letter "H" - it is almost dissolved. If there is a sign "+", the connection does not form a precipitate and reacts with a solvent without a residue. If there is a sign "-", this means that this substance does not exist. Sometimes the same in the table can be seen a sign "?", Then it denotes that the degree of solubility of this compound is not known for certain. Electricity of elements It may vary from 1 to 8, to determine this parameter there is also a special table.

Another useful table is a series of metals. It contains all metals to increase the degree of electrochemical potential. A number of voltage of metals begins with lithium, ends with gold. It is believed that the left is the place in this series of metal, the more active in chemical reactions. In this way, the most active metal It is considered a metal alkaline type of lithium. In the list of elements closer to the end, hydrogen is also present. 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.

Mendeleev Table Pictures in good quality

This scheme is one of the largest achievements in the field of chemistry. Wherein there are a lot of species of this table. - short variant, long, as well as super long. The shortest table is the most common, the long version of the scheme is also often found. It is worth noting that the short version of the scheme is currently not recommended Jewead for use.
Total were more than hundreds of table types have been developeddiffering in submission, form and graphical representation. They are used in different fields of science, or do not apply at all. Currently, new configurations of the scheme continue to be developed by researchers. The main option is used either short or long scheme in excellent quality.

In this lesson, you will learn about the periodic law of Mendeleev, which describes the change in the properties of simple bodies, as well as the forms and properties of the compounds of elements depending on the value of their atomic masses. Consider how it is possible to describe the chemical element in the periodic system.

Topic: Periodic Law andPeriodic system of chemical elements D. I. Mendeleev

Lesson: Description of the element on the position in the periodic system of elements D. I. Mendeleev

In 1869, D.I. Mendeleev based on data accumulated on chemical elements formulated its periodic law. Then he sounded like this: "Properties of simple bodies, as well as the forms and properties of the elements compounds are in periodic dependence on the value of atomic masses of the elements." For a very long time, the physical meaning of the law D.I. Mendeleev was incomprehensible. Everything fell into place after discovering the structure of the atom in the XX century.

Modern formulation of periodic law: "The properties of simple substances, also the forms and properties of the components of the elements are in periodic dependence on the value of the atom nucleus charge."

The charge of the atom nucleus is equal to the number of protons in the kernel. The number of protons is equalized by the number of electrons in the atom. Thus, an atom electrophelane.

Atom nucleus charge in the periodic table is the sequence number of the element.

Period numbershows number of energy levels,on which electrons rotate.

Group numbershows the number of valence electrons.For the elements of the main subgroups, the number of valence electrons is equal to the number of electrons in the external energy level. It is the valence electrons that are responsible for the formation of chemical bonds of the element.

Chemical elements 8 groups - inert gases have 8 electrons on an external electron shell. Such an electronic shell is energetically beneficial. All atoms tend to fill their outer electronic shell to 8 electrons.

What characteristics of the atom change in the periodic system periodically?

The structure of the external electronic level is repeated.

Periodically changing the radius of the atom. In a group radius increaseswith an increase in the number of the period, as the number of energy levels increases. In the period from left to right The growth of the atomic nucleus will occur, but the attraction to the kernel will be larger and therefore the radius of the atom decreases.

Each atom seeks to complete the last energy level in the elements of the group 1 on the last layer 1 electron. Therefore, they are easier to give it. And elements 7 groups are easier to attract 1 electro to the octet. In the group, the ability to give electrons will increase from top to bottom, so ka increases the radius of the atom and attraction to the kernel less. In the period from left to right, the ability to give electrons decreases, because the radius of the atom decreases.

The easier item gives electrons from an external level, the greater metal properties it has, and its oxides and hydroxides have large basic properties. It means that metal properties in groups increase from top to bottom, and in the period right to left. With non-metallic properties, the opposite is the opposite.

Fig. 1. Magnesium position in the table

In the group, magnesium is adjacent to beryllium and calcium. Fig.1. Magnesium is lower than beryllium, but above calcium in the group. Magnesium has more metallic properties than beryllium, but less than calcium. The main properties of its oxides and hydroxides vary also. In the sodium period, it is up to the left, and aluminum right of magnesium. Sodium will show more metallic properties than magnesium, and magnesium is greater, cell aluminum. Thus, you can compare any element with its neighbors by group and period.

Acid and non-metallic properties are changed opposite to basic and metal properties.

The characteristic of chlorine according to its position in the periodic system D.I. Imendeeva.

Fig. 4. Position of chlorine in the table

. The value of the sequence number 17 shows the number of protons17 and electrons17 in the atom. Fig.4. Atomic mass 35 will help calculate the number of neutrons (35-17 \u003d 18). Chlorine is in the third period, it means that the number of energy levels in the atom is equal to 3. It costs in the 7th group, refers to the r- elements. This is nonmetall. Compare chlorine with its neighbors in the group and in the period. The non-metallic properties of chlorine are more than in sulfur, but less than Argon. Chlorine OB-LA-DAY is a mini-Shi-Mal-Tal Lie-Che-MI-MI, than Fluoro and Pain-Shi-Mi than Brom. Issue electrons for energy levels and write an electronic formula. The total distribution of electrons will have such a form. See their. five

Fig. 5. Distribution of electrons of the chlorine atom in power levels

We determine the highest and lower degree of chlorine oxidation. The highest degree of oxidation is +7, as it can give from the last electron electron layer 7. The lower degree of oxidation is -1, because the chlorine is required to completed 1 electron. The formula of higher oxide CL 2 O 7 (acid oxide), HCl hydrogen compound.

In the process of returning or attaching electrons, the atom acquires conditional charge. This conditional charge is called .

- Simple substances have the degree of oxidation equal zero.

Elements may manifest Maximum The degree of oxidation I. minimal. Maximum The degree of oxidation element exhibits when gotall your valence electrons from an external electron level. If the number of valence electrons is equal to the group number, then the maximum degree of oxidation is equal to the number number.

Fig. 2. The position of arsenic in the table

Minimal The degree of oxidation element will take when he vickall possible electrons to complete the electronic layer.

Consider on the example of the element No. 33 the values \u200b\u200bof oxidation degrees.

This is arsenic as. It is located in the fifth main subgroup. Real. In the last electronic level he has five electrons. So, giving them, it will have a degree of oxidation +5. Prior to the completion of the electronic layer, the AS lacks 3 electrons. Attracting them, it will have a degree of oxidation -3.

The position of the elements of metals and non-metals in the periodic system D.I. Mendeleeva.

Fig. 3. Position of metals and non-metals in the table

IN side subgroups are all metals. . If mentally spent diagonal from Bora to Astatu T. above This diagonal in the main subgroups will be all nemetalla , but below this diagonal is all metals. . Fig.3.

1. №№ 1-4 (p.125) Rudzitis G.E. Inorganic and organic chemistry. Grade 8: Tutorial for general education institutions: Basic level / G. E. Rudzitis, F.G. Feldman. M.: Enlightenment. 2011176c.: Il.

2. What characteristics of the atom change the frequency?

3. Give the characteristic of the chemical element of oxygen by its position in the periodic system of D.I. REMEELEEV.

Periodic system of chemical elements (Mendeleev Table) - Classification of chemical elements, which establishes the dependence of the various properties of the elements from the charge of the atomic nucleus. The system is a graphic expression of a periodic law established by the Russian chemist D. I. Mendeleev in 1869. Its initial version was developed by D. I. Mendeleev in 1869-1871 and established the dependence of the properties of the elements on their atomic weight (in modern, from the atomic mass). A total of several hundred options for the image of the periodic system (analytical curves, tables, geometric shapes, etc.) were proposed. In the modern version of the system, it is assumed to form elements in a two-dimensional table, in which each column (group) defines the basic physicochemical properties, and the lines are periods to a certain extent similar to each other.