Krypton is a chemical element. Krypton formula

On our planet, there are many different compounds, organic and mineral substances. So, more than one and a half million structures from the organic world and over 500 thousand outside it are open, synthesized and used by man. And every year this figure is growing, as the development of the chemical industry does not stand still, the countries of the world are actively developing and promoting it.

But it's not even surprising. And the fact that all this variety of substances is built of only 118 chemical elements. That's really cool! The periodic system of chemical elements is the basis that graphically reflects the diversity of the organic and inorganic world.

Classification of chemical elements

There are several options for grading these structures. Thus, Mendeleyev's chemistry table is divided into two groups:

• Elements-metals (most);
• Nonmetals (a smaller part).

In this case, the first is composed of elements that are below the conventional diagonal boundary from boron to astatine, and the second is the ones above. However, there are exceptions to this classification, for example, tin (exists in alpha and beta form, one of which is metal, and the other is nonmetal). Therefore, it is impossible to call such a version of the division absolutely just.

Also, the periodic system of chemical elements can be classified according to the properties of the latter.

1. Possessing basic properties (reducing agents) are typical metals, elements of the 1,2 group of main subgroups (except beryllium).
2. Possessing acid properties (oxidants) are typical non-metals. Elements of 6.7 groups of main subgroups.
3. Amphoteric properties (dual) are all the metals of the subgroups and some of the main ones.
4. Elements are non-metals that manifest themselves as both reducing agents and as oxidants (depending on the reaction conditions).

More often this is how chemical elements are studied. The 8th grade of the school assumes the initial study of all structures with the memorization of the symbol, name and pronunciation in Russian. This is an obligatory condition for the competent mastery of chemistry in the future, the basis of everything. Mendeleyev's chemistry table is always in the field of view of children, but knowing the most common and chemical active of them nevertheless follows.

A special group in this system is the eighth in a row. Its elements of the main subgroup are called inert - noble gases for their completed electronic shells and, as a consequence, low chemical activity. One of them - krypton, a chemical element under the number 36 - will be considered by us in more detail. The rest of his brethren in the table are also noble gases and are used by man very widely.

Krypton is a chemical element

This inhabitant of the Periodic Table is located in the fourth period, the eighth group, the main subgroup. The serial number, and hence the number of electrons, and the charge of the nucleus (the number of protons) = 36. From here we can conclude what will be the electronic formula of krypton. Let's write it: _{+ 36} Kr 1s ² 2s ² 2p ⁶ 3s ² 3p ⁶ 4s ² 3d ¹⁰ 4p ⁶ .

It is obvious that the external energy level of the atom is completely completed. This determines the very low chemical activity of this element. Nevertheless, under certain conditions, it is still possible to cause such stable gas as krypton to enter into some reactions. The chemical element, or rather, its position in the system, the electronic structure, allows one to obtain one more important characteristic of the atom: valence. That is, the ability to form chemical bonds.

Usually, we say that it is almost always for the unexcited state of the atoms equal to the number of the group in which it is (if counted from the first to the fourth in order, and then vice versa, 1234321). However, the valence of krypton in this framework does not fit, since without the message of additional energy, that is, without the excitation of the atom, it is generally absolutely inert and its valence is zero.

If, nevertheless, the excitation of its atom is achieved, the electrons can be resolved and switched to a free 4d orbital. Hence the possible valencies of krypton: 2,4,6. Oxidation degrees corresponding to the sign + (+ 2, + 4, + 6).

History of the discovery

After the discovery of inert gases - argon in 1894, helium in 1985 - to predict and confirm the possibility of the existence of other similar gases in nature, the scientists did not make a special effort. The main efforts on this path were made by W. Ramsay, who also discovered argon. He rightly believed that there are still inert gases in the air, but their number is so insignificant that the technology can not fix their presence.

Therefore, the element of krypton was discovered only after a few years. In 1898, neon gas was released from the air, followed by another inert compound, which for the difficulty of finding and separating was decided to be called krypton. After all, in translation from Greek, "cryptos" means hidden.

To find out for a long time it was not possible, it was very difficult. This fact is confirmed by the fact that one millimeter of gas is contained in one cubic meter of air. That is, the volume is smaller than the thimble! In order to possibly study the matter, it took one hundred cubic centimeters of liquid air. Fortunately, it was during this period that scientists managed to develop methods for obtaining and liquefying air in large quantities. Such a turn of affairs made it possible to win the success of U. Ramsay in the discovery of the element of krypton.

The spectroscopic data confirmed the preliminary conclusions about the new substance. The "hidden" gas has completely new lines in the spectrum, which were not present in any connection at that time.

The resulting simple substance and its formula

If krypton is a chemical element related to inert gases, it is logical to assume that its simple substance will be a volatile molecule. And there is. A simple krypton substance is a monatomic gas with the formula Kr. Usually we are used to seeing gases with the index "2", for example, O ₂ , H ₂ and so on. But this element is different because of its belonging to the family of noble gases and the completed electron shell of the atom.

Physical properties

Like any other compound, this one also has its own characteristics. The physical properties of krypton are as follows.

1. Very heavy gas - three times greater than air.
2. It has no taste.
3. Colorless.
4. It has no smell.
5. The boiling point is -152 ^° C.
6. The density of the substance under ordinary conditions is 3.74 g / l.
7. Melting point -157.3 ⁰ C.
8. The ionization energy is high, 14 eV.
9. Electronegativity is also quite high - 2.6.
10. Soluble in benzene, slightly in water. As the temperature of the liquid increases, the solubility decreases. Also mixed with ethanol.
11. At room temperature, it has a dielectric constant.

Thus, krypton gas has a sufficient number of characteristics to enter into chemical reactions and to be useful to a person with its properties.

Chemical properties

If the krypton (gas) is transferred to a solid state, it crystallizes into a spatial face-centric cubic lattice. In this state, he is also able to enter into chemical reactions. They are very few, but still exist.

There are several types of substances that have been obtained on the basis of krypton.

1. Forms clathrates with water: Kr ^. 5.75H ₂ O.

2. Forms them with organic substances:

• 2.14Kr ^. ₁₂ C ₆ H, OH;
• 2.14Kr ^. 12C ₆ H ₅ CH _3;
• 2Kr ^. CCl ₄ ^. 17H2O;
• 2Kr ^. CHCL ₃ ^. 17H2O;
• 2Kr ^. (CH ₃ ) ₂ CO ^. 17H2O;
• 0.75 Kr ^. 3C ₆ H ₄ (OH) _2.

3. Under severe conditions, it is able to react with fluorine, that is, oxidize. Thus, the krypton formula with the reagent takes the form: KrF _2, or krypton difluoride. The degree of oxidation in the compound is +2.

4. More recently, we managed to synthesize a compound that includes bonds between krypton and oxygen: Kr-O (Kr (OTeF ₅ ) ₂ ).

5. In Finland, an interesting compound of krypton with acetylene, called hydrocryptoacetylene: HKrC≡CH, was obtained.

6. Krypton fluoride (+4) KrF ₄ also exists _. When dissolved in water, this compound is capable of forming a weak and unstable kryptonic acid from which only barium salts BaKrO ₄ are known.

7. The formula of krypton in compounds produced from its difluoride is as follows:

• KrF ⁺ SbF ₆ ^- ;
• Kr ₂ F ₃ ⁺ AuF ₆ ^- .

Thus, it turns out that, despite the chemical inertness, this gas shows restorative properties and is able to enter into chemical interactions under very stringent conditions. This gives chemists around the world the green light in exploring the possibilities of a "hidden" component of the air. It is possible that new compounds will soon be synthesized, which will find wide application in engineering and industry.

Determination of gas

There are several basic ways to determine this gas:

• Chromatography;
• spectroscopy;
• Methods of absorption analysis.

There are several more elements, determined by the same methods, they were also placed in the Mendeleyev table. Krypton, xenon, radon are the heaviest of noble gases and the most elusive. Therefore, for their detection, such complex physicochemical methods are required.

Methods of obtaining

The main method of production is the processing of liquefied air. But because of the small quantitative content of krypton, it has to process millions of cubic meters to extract a small amount of noble gas. In general, the process occurs in three main stages.

1. Air treatment on special air separation columns. In this case, the total flow of substances is divided into heavier fractions-a mixture of hydrocarbons and noble gases in liquid oxygen, and also lighter-numerous impurity gases. Since most of the substances are explosive, there is a special discharge tube in the column, through which the heaviest components are immediately separated. Among them is krypton. At the outlet, it is highly contaminated with foreign impurities. To obtain the purest product, it must be further subjected to a number of specific chemical treatments with special solvents.
2. At this stage, a mixture of krypton and xenon, contaminated with hydrocarbons, is obtained. For cleaning use special devices in which oxidation and adsorption mixture relieve most unnecessary components. At the same time, the very mixture of noble gases remains undivided. In addition, the entire process takes place under high pressure, causing the transition of gases to the liquid state.
3. At the final stage, the final mixture of gases should be separated to produce particularly high-purity krypton and xenon. For this purpose, a special unique installation has been created, technically perfect for this process. The result is a high quality product in the form of gaseous krypton.

It is interesting that all described processes can occur cyclically, without stopping production, if the raw material - air - will be supplied with the right amount. This allows the synthesis of noble gases, including krypton, at very significant industrial scales.

Storage and transportation of the product is carried out in special metal cylinders with the corresponding inscription. They are under pressure, and their storage temperature does not exceed 20 ^° C.

Content in nature

In natural conditions, not just an element of krypton, but its isotopes, is contained. There are six varieties that are stable in nature:

• Krypton-78 - 0.35%;
• Krypton-80 - 2.28%;
• Krypton-82 - 11.58%;
• Krypton-83 - 11.49%;
• Krypton-84 - 57%;
• Krypton-86 - 17.3%.

Where is the gas contained? Of course, there, where it was first allocated - in the air. The percentage is very small - only 1.14 * 10 ^-4 %. Also, the constant replenishment of these precious gas reserves in nature is due to nuclear reactions within the Earth's lithosphere. It is there that a significant part of the stable isotopic varieties of this element is formed.

Using Man

Modern technology makes it possible to obtain krypton from air in large quantities. And there is every reason to assume that he will soon replace the inert argon in electric bulbs. After all, filled with krypton, they will become more economical: at the same energy consumption they will serve much longer and shine brighter. It is also better to withstand overloads, compared to conventional ones, which are filled with a mixture of nitrogen and argon.

This can be explained by the inactivity of large and heavy krypton molecules, which slow the transfer of heat from the lamp glass to the filament and reduce the evaporation of the atoms of matter from its surface.

Also, the radioactive isotope krypton ⁸⁵ Kr is used to fill special lamps, since it can emit beta rays. This energy of radiation turns into visible light. Such lamps consist of a glass cylinder, the inner walls of which are covered with a phosphorescent compound. The beta rays of the krypton isotope, falling on this layer, cause its luminescence, which is clearly visible even at a distance of 500 m.

At a distance of up to 3 meters, you can clearly see even the printed text. Lamps are durable, since the half-life of the isotope krypton 85 is about 10 years. The devices operate regardless of the current source and external conditions.

Krypton fluorides are also used as oxidants for rocket fuel. The Kr-F compound is used in the production of excimer lasers. Some isotopes of krypton are used in medicine. Mainly for the diagnostics of equipment, detection of perforations and leaks in vacuum installations, prediction and detection of corrosion, as a control over the wear of equipment parts.

Another option for using krypton is X-ray tubes, which are filled with them. Modern scientists are looking for ways to use this gas as a filler in the composition of breathing mixtures for immersion in water. It can be realized using it as an anesthetic in medicine.