On our planet, there are many different compounds, organic and mineral substances.So, a man openly, synthesized and used more than half a million of the world's organic structures, and more than 500 thousand out of it.And each year this figure is growing, because the development of the chemical industry is not in place, countries are actively developing and promoting it.
But even this is not surprising.And the fact that all this variety of substances built of only 118 chemicals.That's really cool!Periodic Table of Elements is the foundation, which graphically reflects the diversity of the organic and inorganic world.
classification of chemical elements
There are several options gradation data structures.Thus, the periodic table in chemistry conditionally divided into two groups:
- metal elements (the majority);
- non-metals (lower part).
In this first of the constituent elements that are below the conventional boundaries of the diagonal of boron to astatine, and the second - the ones above.However, there are exceptions to this classification, for example, tin (exists in the alpha and beta forms, one of which - the metal, and the other - a nonmetal).Therefore, this option is called the separation can not be absolutely fair.
also periodic system of chemical elements can be classified by the properties of the latter.
- have basic properties (reducing) - typical of metals, elements of main sub-groups of 1.2 (except for beryllium).
- have acidic properties (oxidants) - typical non-metals.6.7 Elements of the main groups, sub-groups.
- amphoteric properties (dual) - all metals subgroups and by some of the top.
- element nonmetals manifests itself as reducing agents and as oxidants (depending on reaction conditions).
Most exactly studied chemical elements.Grade 8 school was originally intended to study all the structures of remembering the character names and the pronunciation in Russian.This is a prerequisite for a competent mastering chemistry in the future, the basis of everything.Periodic table in chemistry is always in the field of view of children, but to know the most common and reactivity of them should still be.
special group in this system takes the eighth.Its main group elements are called rare - noble - gas for their completed electronic shells and, as a consequence, low chemical activity.One of them - Krypton, a chemical element at number 36 - will be discussed by us in detail.The rest of his colleagues on the table are also noble gases and are used widely by man.
Krypton - a chemical element
This inhabitant of the periodic system is located in the fourth period, the eighth group, the main subgroups.Serial number, and hence the number of electrons and the nuclear charge (number of protons) = 36. It can be concluded that a formula will be e-krypton.We write it: + 36Kr 1s22s22p63s23p64s23d104p6.
Obviously, the external energy level of the atom is fully completed.This determines the very low reactivity of this element.Nevertheless, under certain conditions, still manages to get engage in some reactions a stable gas such as krypton.The chemical element, or rather, his position in the system, electronic structure, and allow to obtain another important characteristic of the atom valence.That is, the capacity to form chemical bonds.
Usually we say that it is almost always for the unexcited state of the atoms is the group number, in which it is located (if you count from the first to fourth in order, and then vice versa, 1234321).However, the valence of krypton in this framework does not fit, because no additional energy posts, that is, without the excitation of the atom, he did absolutely inert and its valence is zero.
If you still get excited by the atom, the electrons can pair-breaking and the transition to a free 4d orbital.Hence the possible valence krypton: 2,4,6.Oxidation corresponding with + (+ 2 + 4 + 6).
History of discovery
After opening the inert gases - argon in 1894, helium in 1985 - to predict and confirm the possible existence in nature other gases much difficulty for scientists is not reached.The main efforts in this direction exerted W. Ramsay, who discovered argon.He rightly believed that there is still air in inert gases, but their number is so insignificant that the technology can not fix their presence.Therefore
element krypton was opened just a few years.In 1898 the air was isolated neon gas, and after him and other inert compound that is the difficulty of finding and isolating it was decided to name krypton.It is translated from the Greek "Kryptos" means hidden.
detect a long time it was not possible, it was very difficult.It confirms the fact that in one cubic meter of air contains one milliliter of gas.That is, the amount is less than a thimble!It was possible to examine the substance, it took one hundred cubic centimeters of liquid air.Fortunately, during this period, scientists were able to develop methods for producing and liquefying air in large quantities.Such a turn of events allowed to gain success in the opening W. Ramsay element krypton.
spectroscopic data confirmed the preliminary findings of a new substance."Hidden" gas has a whole new line in the spectrum, which was not in any connection at that time.
Formed simple substance and its formula
If krypton - a chemical element belonging to the inert gas, it is logical to assume that it would be a simple matter volatile molecules.And there is.Simple stuff krypton - a monatomic gas with the formula Kr.Typically we used visible gases with index '2', for example, O2, H2, and so on.But this element is different because of belonging to a family of noble gases and complete electron shell of an atom.
physical properties
As with any other compounds in this also has its own characteristics.Physical properties as follows krypton.
- Very heavy gas - three times higher than air.
- has no taste.
- colorless.
- odor.
- boiling point of -152 0C.
- density of the substance at normal conditions, 3.74 g / l.
- Melting point -157.3 0C.
- high ionization energy is 14 eV.
- Electronegativity is also quite high - 2.6.
- soluble in benzene, slightly in water.With increasing temperature the solubility of the fluid decreases.Also mixed with ethanol.
- at room temperature has a permittivity.
Thus, krypton gas has enough features to enter into chemical reactions and be a useful person to their properties.
chemical properties
Translated Krypton (gas) in the solid state, it crystallizes in a cubic lattice spatial granetsentricheskuyu.In this state, he is also able to enter into chemical reactions.They are few, but nevertheless exist.
There are several types of substances that were obtained on the basis of krypton.
1. Forms clathrates with water: Kr.5,75N2O.
2. Forms of the same organic substances:
- 2,14Kr.12S6N, OH;
- 2,14Kr.12S6N5SN3;
- 2Kr.CCl4.17H2O;
- 2Kr.CHCL3.17H2O;
- 2Kr. (CH3) 2SO.17H2O;Kr.ZS6N4
- 0,75 (OH) 2.
3. The stringent conditions can react with fluorine, i.e. oxidized.Thus, the formula krypton reagent becomes: KrF2, or krypton difluoride.The oxidation state of the compound 2.
4. Relatively recently succeeded in synthesizing a compound which includes links between krypton and oxygen: Kr-O (Kr (OTeF5) 2).
5. Finland has got an interesting mix of krypton with acetylene called gidrokriptoatsetilen: HKrC≡CH.
6. Krypton Fluoride (4) there is also a KrF4.When dissolved in water, this compound is able to form a weak and unstable krypton acid, from which the only known barium salt: BaKrO4.
7. Formula krypton in the compounds produced by it difluoride looks like:
- KrF + SbF6-;
- Kr2F3 + AuF6-.
Thus, it turns out that, despite the chemical inertia, this gas exhibits reducing properties and is able to enter into chemical reactions with very stringent conditions.This gives chemists all over the world the green light in the study opportunities "hidden" component of air.It is possible that soon will be synthesized new compounds that will be widely used in engineering and industry.
Determination gas
There are several ways of determining the gas:
- chromatography;
- spectroscopy;
- absorption analysis methods.
There are a few elements determined by the same methods, they also placed a periodic table.Krypton, xenon and radon - the heaviest of the noble gases and the most elusive.Therefore, for the detection and require such complex physical and chemical methods.
Methods for producing
main way of getting - a processing liquid air.But because of the small quantitative content krypton it has to process millions of cubic meters for production of a small amount of noble gas.The whole process takes place in three main steps.
- Processing Air special air separation columns.Thus there is a total separation of the flow of substances heavier fraction - the mixture of hydrocarbon and noble gas in liquid oxygen, as well as lighter - numerous impurity gases.Since most of the explosive substances, the column has a special outlet hose, on which once separated the heaviest components.Among them, and krypton.At the exit, he is heavily polluted by foreign matter.To obtain a pure product, it needs to be further subjected to a number of specific chemical treatments with special solvents.
- At this stage, a mixture of krypton and xenon, contaminated with hydrocarbons.For cleaning using special devices in which the oxidation and the adsorption of the mixture eliminate most unwanted components.This noble gas mixture itself remains undivided among themselves.Moreover, the whole process takes place under high pressure, causing the transition gas in liquid state.
- At the final stage should be the separation of the final gas mixture to produce a very high purity krypton and xenon.For this purpose a special unique installation is technically perfect for this process.The result is a high quality product in the form of gaseous krypton.
interesting that all these processes can occur in cycles, without stopping production, if the raw materials - the air - will come due amount.This allows the synthesis of noble gases including krypton, in very large industrial scale.
Storage and transport of the product is carried out in special metal containers with an appropriate inscription.They are under pressure and temperature of storage shall not exceed 20 0C.
Content in nature
Under natural conditions, there are not just the element krypton and its isotopes.In total there are six varieties resistant to natural conditions:
- krypton-78 - 0.35%;
- krypton-80 - 2.28%;
- krypton-82 - 11.58%;
- krypton-83 - 11.49%;
- krypton-84 - 57%;
- krypton-86 - 17.3%.
Where also contains this gas?Of course there is, and where he was singled out for the first time - in the air.The percentage is very small - just 1.14 * 10-4%.Also, constant updating of the data of a noble gas reserves in nature is due to the nuclear reactions within the Earth's lithosphere.It was there that the significant part of stable isotope varieties of this element.
Human uses
Modern technology allows to obtain krypton from the air in large quantities.And there is every reason to believe that he will soon replace the inert argon light bulbs.After all, filled with krypton, they will become more economical: with the same power consumption, they will serve much longer and shine brighter.Also better withstand overload compared with conventional, which are filled with a mixture of nitrogen and argon.
This can be explained by the large and slow-moving heavy molecules krypton, which slow the transfer of heat from the glass bulb to the filament and reduce the evaporation of atoms of matter from its surface.
also radioactive isotope krypton 85Kr used for filling special lamps, as capable of emitting beta rays.This radiation energy is converted into visible light.These lamps consist of a glass bulb whose inner walls are coated with a phosphorescent composition.Beta rays isotope krypton, getting on this layer, causing it glow that perfectly noticeable even at a distance of 500 m.
At a distance of 3 meters can be clearly seen even printed text.Lamps are durable, since the half-life of the isotope krypton 85 is about 10 years.Work device independently of the current source and the external environment.
also krypton fluoride are used as rocket fuel oxidizer.The compound composition Kr-F is used in the production of excimer lasers.Some isotopes of krypton are used in medicine.Generally for diagnostic equipment, the detection of perforations and leaks in vacuum systems, the prediction and detection of corrosion as the control equipment wear and tear.
Another usage of krypton - a X-ray tubes that are filled with them.Modern scientists are seeking ways to use this gas as a filler in the composition of breathing mixtures for immersion in water.It can be implemented, and its use as an anesthetic in medicine.
