Oxygen O has atomic number 8, located in the main subgroup (subgroup a) VI group, in the second period. In oxygen atoms, valence electrons are located at the 2nd energy level, which has only s- and p-orbital. This excludes the possibility of the transition of O atoms to an excited state, therefore oxygen in all compounds exhibits a constant valence equal to II. Having a high electronegativity, oxygen atoms in compounds are always negatively charged (s.r. \u003d -2 or -1). The exception is fluorides OF 2 and O 2 F 2.

For oxygen, the oxidation states are -2, -1, +1, +2

General characteristics of the element

Oxygen is the most abundant element on Earth, accounting for slightly less than half, 49% of the total mass of the earth's crust. Natural oxygen consists of 3 stable isotopes 16 O, 17 O and 18 O (16 O prevails). Oxygen is part of the atmosphere (20.9% by volume, 23.2 by weight), water and more than 1400 minerals: silica, silicates and aluminosilicates, marbles, basalts, hematite and other minerals and rocks. Oxygen makes up 50-85% of the mass of tissues of plants and animals, because it is contained in proteins, fats and carbohydrates that make up living organisms. The role of oxygen for respiration and for oxidation processes is well known.

Oxygen is relatively little soluble in water - 5 volumes in 100 volumes of water. However, if all the oxygen dissolved in water passed into the atmosphere, it would occupy a huge volume - 10 million km 3 (n.u). This is equal to about 1% of all oxygen in the atmosphere. The formation of an oxygen atmosphere on earth is due to the processes of photosynthesis.

Discovered by the Swede K. Scheele (1771 - 1772) and the Englishman J. Priestley (1774). The first used heating of nitrate, the second - mercury oxide (+2). The name was given by A. Lavoisier ("oxygenium" - "giving birth to acids").

In free form, it exists in two allotropic modifications - "ordinary" oxygen O 2 and ozone O 3.

Ozone molecule structure

3O 2 \u003d 2O 3 - 285 kJ
Ozone in the stratosphere forms a thin layer that absorbs most of the biologically harmful ultraviolet radiation.
During storage, ozone spontaneously converts to oxygen. Chemically, oxygen O 2 is less active than ozone. The electronegativity of oxygen is 3.5.

Physical properties of oxygen

O 2 - gas without color, odor and taste, so pl. –218.7 ° С, b.p. –182.96 ° C, paramagnetic.

Liquid O 2 is blue, solid is blue. O 2 is soluble in water (better than nitrogen and hydrogen).

Oxygen production

1. Industrial method - liquid air distillation and water electrolysis:

2H 2 O → 2H 2 + O 2

2. In the laboratory, oxygen is obtained:
1.Electrolysis of alkaline aqueous solutions or aqueous solutions of oxygen-containing salts (Na 2 SO 4, etc.)

2. Thermal decomposition of potassium permanganate KMnO 4:
2KMnO 4 \u003d K 2 MnO4 + MnO 2 + O 2,

Berthollet's salt KClO 3:
2KClO 3 \u003d 2KCl + 3O 2 (catalyst MnO 2)

Manganese oxide (+4) MnO 2:
4MnO 2 \u003d 2Mn 2 O 3 + O 2 (700 o C),

3MnO 2 \u003d 2Mn 3 O 4 + O 2 (1000 o C),

Barium peroxide BaO 2:
2BaO 2 \u003d 2BaO + O 2

3. By decomposition of hydrogen peroxide:
2H 2 O 2 \u003d H 2 O + O 2 (catalyst MnO 2)

4. Decomposition of nitrates:
2KNO 3 → 2KNO 2 + O 2

On spaceships and submarines, oxygen is obtained from a mixture of K 2 O 2 and K 2 O 4:
2K 2 O 4 + 2H 2 O \u003d 4KOH + 3O 2
4KOH + 2CO 2 \u003d 2K 2 CO 3 + 2H 2 O

In total:
2K 2 O 4 + 2CO 2 \u003d 2K 2 CO 3 + 3О 2

When using K 2 O 2, the overall reaction looks like this:
2K 2 O 2 + 2CO 2 \u003d 2K 2 CO 3 + O 2

If you mix K 2 O 2 and K 2 O 4 in equal molar (ie equimolar) amounts, then one mole of O 2 will be released per 1 mole of absorbed CO 2.

Chemical properties of oxygen

Oxygen supports combustion. Combustion - b rapid oxidation process of a substance, accompanied by the release of a large amount of heat and light. To prove that the bottle contains oxygen, and not some other gas, a smoldering splinter must be dipped into the bottle. In oxygen, a smoldering splinter flares up brightly. Combustion of various substances in air is a redox process in which oxygen is the oxidizing agent. Oxidants are substances that "take" electrons from reducing substances. The good oxidizing properties of oxygen can be easily explained by the structure of its outer electron shell.

The oxygen valence shell is located at the 2nd level - relatively close to the nucleus. Therefore, the nucleus strongly attracts electrons to itself. On the valence shell of oxygen 2s 2 2p 4 there are 6 electrons. Consequently, two electrons are missing to the octet, which oxygen seeks to accept from the electron shells of other elements, reacting with them as an oxidizing agent.

Oxygen has the second (after fluorine) electronegativity in the Pauling scale. Therefore, in the overwhelming majority of its compounds with other elements, oxygen has negative oxidation state. A stronger oxidant than oxygen is only its neighbor in the period - fluorine. Therefore, oxygen compounds with fluorine are the only ones where oxygen has a positive oxidation state.

So, oxygen is the second most powerful oxidizing agent among all elements of the Periodic Table. Most of its most important chemical properties are associated with this.
All elements react with oxygen, except for Au, Pt, He, Ne and Ar, in all reactions (except for interaction with fluorine) oxygen is an oxidizing agent.

Oxygen easily reacts with alkali and alkaline earth metals:

4Li + O 2 → 2Li 2 O,

2K + O 2 → K 2 O 2,

2Ca + O 2 → 2CaO,

2Na + O 2 → Na 2 O 2,

2K + 2O 2 → K 2 O 4

Fine iron powder (so-called pyrophoric iron) ignites spontaneously in air, forming Fe 2 O 3, and a steel wire burns in oxygen if it is heated in advance:

3 Fe + 2O 2 → Fe 3 O 4

2Mg + O 2 → 2MgO

2Cu + O 2 → 2CuO

Oxygen reacts with non-metals (sulfur, graphite, hydrogen, phosphorus, etc.) when heated:

S + O 2 → SO 2,

C + O 2 → CO 2,

2H 2 + O 2 → H 2 O,

4P + 5O 2 → 2P 2 O 5,

Si + O 2 → SiO 2, etc.

Almost all reactions involving oxygen O 2 are exothermic, with rare exceptions, for example:

N 2 + O 2 → 2NO - Q

This reaction takes place at temperatures above 1200 o C or in an electric discharge.

Oxygen is capable of oxidizing complex substances, for example:

2H 2 S + 3O 2 → 2SO 2 + 2H 2 O (excess oxygen),

2H 2 S + O 2 → 2S + 2H 2 O (lack of oxygen),

4NH 3 + 3O 2 → 2N 2 + 6H 2 O (without catalyst),

4NH 3 + 5O 2 → 4NO + 6H 2 O (in the presence of a Pt catalyst),

CH 4 (methane) + 2O 2 → CO 2 + 2H 2 O,

4FeS 2 (pyrite) + 11O 2 → 2Fe 2 O 3 + 8SO 2.

Known compounds containing dioxygenyl cation O 2 +, for example, O 2 + - (the successful synthesis of this compound prompted N. Bartlett to try to obtain compounds of inert gases).

Ozone

Ozone is chemically more reactive than oxygen O 2. So, ozone oxidizes iodide - ions I - in a Kl solution:

O 3 + 2Kl + H 2 O \u003d I 2 + O 2 + 2KOH

Ozone is highly toxic, its toxic properties are stronger than, for example, hydrogen sulfide. However, in nature, ozone contained in the high layers of the atmosphere plays the role of a protector of all life on Earth from the harmful ultraviolet radiation of the sun. A thin ozone layer absorbs this radiation and does not reach the Earth's surface. There are significant fluctuations in the thickness and length of this layer over time (the so-called ozone holes), the reasons for such fluctuations have not yet been clarified.

Oxygen application O 2: to intensify the processes of obtaining cast iron and steel, when smelting non-ferrous metals, as an oxidizer in various chemical industries, for life support on submarines, as an oxidizer for rocket fuel (liquid oxygen), in medicine, when welding and cutting metals.

Ozone O 3 application: for disinfection of drinking water, waste water, air, for bleaching fabrics.

OXYGEN (Latin Oxygenium), O, chemical element of group VI of short form (16th group of long form) of the periodic system, belongs to chalcogenes; atomic number 8, atomic mass 15.9994. Natural oxygen consists of three isotopes: 16 O (99.757%), 17 O (0.038%) and 18 O (0.205%). The predominance of the lightest isotopes 16 O in the mixture is due to the fact that the nucleus of the 16 O atom consists of 8 protons and 8 neutrons. The equal number of protons and neutrons determines the high energy of their binding in the nucleus and the greatest stability of 16 O nuclei in comparison with the rest. Radioisotopes with mass numbers 12-26 have been artificially obtained.

Historical reference. Oxygen was obtained in 1774 independently by K. Scheele (by calcining potassium nitrates KNO 3 and sodium NaNO 3, manganese dioxide MnO 2 and other substances) and J. Priestley (by heating lead tetroxide Pb 3 O 4 and mercury oxide HgO). Later, when it was found that oxygen is part of acids, A. Lavoisier proposed the name oxygène (from the Greek όχύς - sour and γεννάω - I give birth, hence the Russian name "oxygen").

Distribution in nature. Oxygen is the most common chemical element on Earth: the content of chemically bound oxygen in the hydrosphere is 85.82% (mainly in the form of water), in the earth's crust -49% by weight. More than 1400 minerals are known, which include oxygen. They are dominated by minerals formed by salts of oxygen-containing acids (the most important classes are natural carbonates, natural silicates, natural sulfates, natural phosphates), and rocks based on them (for example, limestone, marble), as well as various natural oxides, natural and mountain hydroxides. rocks (for example, basalt). Molecular oxygen makes up 20.95% by volume (23.10% by mass) of the earth's atmosphere. Oxygen in the atmosphere is of biological origin and is formed in green plants containing chlorophyll, from water and carbon dioxide during photosynthesis. The amount of oxygen released by plants compensates for the amount of oxygen consumed in the processes of decay, combustion, and respiration.

Oxygen - a biogenic element - is part of the most important classes of natural organic compounds (proteins, fats, nucleic acids, carbohydrates, etc.) and in the composition of inorganic compounds of the skeleton.

Properties... The structure of the outer electron shell of the oxygen atom 2s 2 2p 4; in compounds it exhibits oxidation states -2, -1, rarely +1, +2; Pauling electronegativity 3.44 (the most electronegative element after fluorine); atomic radius 60 pm; the radius of the O 2 ion is 121 pm (coordination number 2). In gaseous, liquid and solid states, oxygen exists in the form of diatomic O 2 molecules. O 2 molecules are paramagnetic. There is also an allotropic modification of oxygen - ozone, which consists of triatomic O 3 molecules.

In the ground state, an oxygen atom has an even number of valence electrons, two of which are not paired. Therefore, oxygen, which does not have a vacant d-orbital low in energy, is bivalent in most chemical compounds. Depending on the nature of the chemical bond and the type of the crystal structure of the compound, the coordination number of oxygen can be different: O (atomic oxygen), 1 (for example, O 2, CO 2), 2 (for example, H 2 O, H 2 O 2), 3 (for example, H 3 O +), 4 (for example, Be and Zn oxoacetates), 6 (for example, MgO, CdO), 8 (for example, Na 2 O, Cs 2 O). Due to the small radius of the atom, oxygen is able to form strong π-bonds with other atoms, for example, with oxygen atoms (O 2, O 3), carbon, nitrogen, sulfur, phosphorus. Therefore, for oxygen, one double bond (494 kJ / mol) is energetically more favorable than two simple ones (146 kJ / mol).

The paramagnetism of O 2 molecules is explained by the presence of two unpaired electrons with parallel spins on doubly degenerate antibonding π * orbitals. Since there are four more electrons on the bonding orbitals of the molecule than on the antibonding ones, the bond order in O 2 is 2, that is, the bond between the oxygen atoms is double. If two electrons with opposite spins appear on the same π * orbital during photochemical or chemical action, the first excited state appears, which is 92 kJ / mol higher in energy than the ground state. If, upon excitation of an oxygen atom, two electrons occupy two different π * orbitals and have opposite spins, a second excited state arises, the energy of which is 155 kJ / mol higher than the ground state. Excitation is accompanied by an increase in the O - O interatomic distances: from 120.74 pm in the ground state to 121.55 pm for the first and up to 122.77 pm for the second excited state, which, in turn, leads to a weakening of the O - O bond and to increased chemical activity of oxygen. Both excited states of the O 2 molecule play an important role in oxidation reactions in the gas phase.

Oxygen is a colorless, odorless and tasteless gas; t pl -218.3 ° C, bale -182.9 ° C, density of gaseous oxygen 1428.97 kg / dm 3 (at 0 ° C and normal pressure). Liquid oxygen is a pale blue liquid, solid oxygen is a blue crystalline substance. At 0 ° C, thermal conductivity is 24.65-10 -3 W / (mK), molar heat capacity at constant pressure is 29.27 J / (mol · K), dielectric constant of gaseous oxygen is 1.000547, liquid oxygen is 1.491. Oxygen is poorly soluble in water (3.1% oxygen by volume at 20 ° C), well soluble in some organofluorine solvents, for example, perfluorodecalin (4500% oxygen by volume at 0 ° C). A significant amount of oxygen is dissolved by noble metals: silver, gold and platinum. The gas solubility in molten silver (2200% by volume at 962 ° C) sharply decreases with decreasing temperature, therefore, when cooled in air, the silver melt “boils” and splashes out due to the intense release of dissolved oxygen.

Oxygen is highly reactive, a strong oxidizing agent: it interacts with most simple substances under normal conditions, mainly with the formation of the corresponding oxides (many reactions that proceed slowly at room and lower temperatures are accompanied by an explosion and the release of a large amount of heat when heated). Oxygen interacts under normal conditions with hydrogen (water H 2 O is formed; mixtures of oxygen with hydrogen are explosive - see Oxyhydrogen gas), when heated - with sulfur (sulfur dioxide SO 2 and sulfur trioxide SO 3), carbon (carbon oxide CO, carbon dioxide CO 2), phosphorus (phosphorus oxides), many metals (metal oxides), especially easily with alkali and alkaline earth (mainly metal peroxides and superoxides, for example barium peroxide BaO 2, potassium superoxide KO 2). Oxygen interacts with nitrogen at temperatures above 1200 ° C or when exposed to an electric discharge (nitrogen monoxide NO is formed). Oxygen compounds with xenon, krypton, halogens, gold and platinum are obtained indirectly. Oxygen does not form chemical compounds with helium, neon and argon. Liquid oxygen is also a strong oxidizing agent: the cotton soaked in it instantly burns out when ignited, some volatile organic substances can spontaneously ignite when they are at a distance of several meters from an open vessel with liquid oxygen.

Oxygen forms three ionic forms, each of which determines the properties of a separate class of chemical compounds: O 2 - superoxides (the formal oxidation state of the oxygen atom is -0.5), O 2 - - peroxide compounds (the oxidation state of the oxygen atom is -1, for example hydrogen peroxide H 2 О 2), О 2- - oxides (the oxidation state of the oxygen atom is -2). Oxygen exhibits positive oxidation states +1 and +2 in fluorides О 2 F 2 and OF 2, respectively. Oxygen fluorides are unstable and are strong oxidants and fluorinating reagents.

Molecular oxygen is a weak ligand and is attached to some complexes of Fe, Co, Mn, Cu. Among such complexes, the most important is iron porphyrin, which is part of hemoglobin, a protein that carries oxygen in the body of warm-blooded animals.

Biological role... Oxygen, both in free form and in the composition of various substances (for example, enzymes of oxidases and oxidoreductases), takes part in all oxidative processes that occur in living organisms. As a result, a large amount of energy is released, which is expended in the process of life.

Receiving... On an industrial scale, oxygen is produced by liquefaction and fractional distillation of air (see Air separation in the article), as well as by electrolysis of water. Under laboratory conditions, oxygen is obtained by decomposition by heating hydrogen peroxide (2P 2 O 2 \u003d 2H 2 O + O 2), metal oxides (for example, mercury oxide: 2HgO \u003d 2Hg + O 2), salts of oxygen-containing oxidizing acids (for example, potassium chlorate : 2KlO 3 \u003d 2KCl + 3O 2, potassium permanganate: 2KMnO 4 \u003d K 2 MnO 4 + MnO 2 + O 2), electrolysis of an aqueous solution of NaOH. Gaseous oxygen is stored and transported in steel cylinders painted blue at a pressure of 15 and 42 MPa, liquid oxygen - in metal Dewar vessels or in special tanks.

Application... Industrial oxygen is used as an oxidizing agent in metallurgy (see, for example, the BOF process), in the flame treatment of metals (see, for example, Oxyfuel cutting), in the chemical industry for the production of artificial liquid fuel, lubricating oils, nitric and sulfuric acids, methanol, ammonia and ammonia fertilizers, metal peroxides, etc. Pure oxygen is used in oxygen-breathing apparatus on spacecraft, submarines, when climbing to great heights, conducting underwater work, for medicinal purposes in medicine (see the article Oxygen therapy). Liquid oxygen is used as an oxidizing agent for rocket fuels in blasting operations. Aqueous emulsions of solutions of gaseous oxygen in some organofluorine solvents have been proposed to be used as artificial blood substitutes (for example, perftoran).

Lit .: Saunders N. Oxygen and the elements of group 16. Oxf., 2003; Drozdov A.A., Zlomanov V.P., Mazo G.N., Spiridonov F.M. Inorganic chemistry. M., 2004. T. 2; Shriver D., Atkins P. Inorganic chemistry. M., 2004. T. 1-2.

Oxygen - a chemical element, the properties of which will be discussed in the next few paragraphs. Let's turn to the Periodic Table of Chemical Elements of D.I. Mendeleev. The element oxygen is located in the 2nd period, VI group, the main subgroup.

It is also indicated there that the relative atomic mass of oxygen is 16.

By the ordinal number of oxygen in the Periodic System, one can easily determine the number of electrons contained in its atom, the charge of the oxygen atom nucleus, the number of protons.

The oxygen valence in most compounds is II. The oxygen atom can attach two electrons and turn into an ion: O0 + 2ē \u003d O − 2.

It should be noted that oxygen is the most abundant element on our planet. Oxygen is part of the water. Sea and fresh waters are 89% by weight oxygen. Oxygen is found in many minerals and rocks. The mass fraction of oxygen in the earth's crust is about 47%. The air contains about 23% oxygen by mass.

Physical properties of oxygen

When two oxygen atoms interact, a stable molecule of a simple substance oxygen O2 is formed. This simple substance, like the element, is called oxygen. Don't confuse the element oxygen and oxygen is a simple substance!

Physical properties oxygen - a colorless, odorless and tasteless gas. Practically insoluble in water (at room temperature and normal atmospheric pressure, the solubility of oxygen is about 8 mg per liter of water).

Oxygen is soluble in water - 31 ml of oxygen (0.004% by weight) dissolves in 1 liter of water at a temperature of 20 ° C. However, this amount is sufficient for the respiration of fish living in water bodies. Oxygen gas is slightly heavier than air: 1 liter of air at 0 ° C and normal pressure weighs 1.29 g, and 1 liter of oxygen weighs 1.43 g.

Oxygen exhibits interesting properties when cooled strongly. So, at a temperature -183 ° C oxygen is condensed into a transparent, mobile liquid, pale blue in color.

If liquid oxygen is cooled even more, then at a temperature –218 ° C oxygen "freezes" in the form of blue crystals. If the temperature is gradually increased, then at –218 ° С, solid oxygen will begin to melt, and when -183 ° C - will boil. Consequently, the boiling and condensing temperatures, as well as the freezing and melting temperatures for substances are the same.

For storage and transportation of liquid oxygen, so-called Dewar vessels are used.... Dewar vessels are used for storing and transporting liquids, the temperature of which must remain constant for a long time. The Dewar vessel is named after its inventor, Scottish physicist and chemist James Dewar.

The simplest Dewar vessel is a household thermos. The design of the vessel is quite simple: it is a flask placed in a large flask. Air is evacuated from the sealed space between the flasks. Due to the absence of air between the walls of the flasks, the liquid poured into the inner flask does not cool down or heat up for a long time.

Oxygen is a paramagnetic substance, that is, in liquid and solid states, it is attracted by a magnet

There is another simple substance in nature, consisting of oxygen atoms. This is ozone. Chemical formula of ozone O3. Ozone, like oxygen, is a gas under normal conditions. Ozone is generated in the atmosphere during lightning discharges. The characteristic smell of freshness after a thunderstorm is the smell of ozone.

If ozone is obtained in a laboratory and a significant amount of it is collected, then in high concentrations ozone will have a pungent unpleasant odor. Ozone is obtained in the laboratory in special devices - ozonizers. Ozonizer - a glass tube into which a current of oxygen is supplied and an electrical discharge is created. An electrical discharge converts oxygen to ozone:

Unlike colorless oxygen, ozone is a blue gas. The solubility of ozone in water is about 0.5 liters of gas per liter of water, which is significantly higher than that of oxygen. Taking this property into account, ozone is used to disinfect drinking water, as it has a detrimental effect on pathogens.

At low temperatures, ozone behaves similarly to oxygen. At a temperature of -112 ° C, it condenses into a violet liquid, and at a temperature of -197 ° C, it crystallizes in the form of dark violet, almost black crystals.

Thus, we can conclude that the atoms of the same chemical element can form different simple substances.

The phenomenon of the existence of a chemical element in the form of several simple substances is called allotropy.

Simple substances formed by the same element are called allotropic modifications

Hence, oxygen and ozone are allotropic modifications of the chemical element oxygen. There is evidence that at ultra-low temperatures, in a liquid or solid state, oxygen can exist in the form of O4 and O8 molecules.

Oxygen cycle in nature

The amount of oxygen in the atmosphere is constant. Consequently, the consumed oxygen is constantly replenished with new one.

The most important sources of oxygen in nature are carbon dioxide and water. Oxygen enters the atmosphere mainly as a result of the process of photosynthesis in plants, according to the reaction scheme:

CO2 + H2O → C6H12O6 + O2.

Oxygen can also form in the upper layers of the Earth's atmosphere: due to exposure to solar radiation, water vapor partially decomposes to form oxygen.

Oxygen is consumed during respiration, fuel combustion, oxidation of various substances in living organisms, and oxidation of inorganic substances found in nature. Large quantities of oxygen are consumed in technological processes such as steelmaking.

The oxygen cycle in nature can be represented as a diagram:

• Oxygen - an element of the VI group, the main subgroup, 2 periods of the D.I. Mendeleev
• The element oxygen forms in nature two allotropic modifications: oxygen O2 and ozone O3
• The phenomenon of the existence of a chemical element in the form of several simple substances is called allotropy.
• Simple substances are called allotropic modifications.
• Oxygen and ozone have different physical properties
• Oxygen - a colorless, odorless gas, taste, practically insoluble in water, at a temperature of -183 ° C condenses into a pale blue liquid. At a temperature of –218 ° С it crystallizes in the form of blue crystals
• Ozone - blue gas with a pungent unpleasant odor. Let's well dissolve in water. At a temperature of -112 ° C, it condenses into a violet liquid, crystallizes in the form of dark violet, almost black crystals, at a temperature of -197 ° C
• Liquid oxygen, ozone and other gases are stored in Dewars

Oxygen formsperoxides with the oxidation state -1.
- For example, peroxides are produced by the combustion of alkali metals in oxygen:
2Na + O 2 → Na 2 O 2

- Some oxides absorb oxygen:
2BaO + O 2 → 2BaO 2

- According to the combustion principles developed by A. N. Bach and K. O. Engler, oxidation occurs in two stages with the formation of an intermediate peroxide compound. This intermediate can be isolated, for example, when the flame of burning hydrogen is cooled with ice, along with water, hydrogen peroxide is formed:
H 2 + O 2 → H 2 O 2

Superoxides have an oxidation state of -1/2, that is, one electron per two oxygen atoms (ion O 2 -). Produced by the interaction of peroxides with oxygen at elevated pressures and temperatures:
Na 2 O 2 + O 2 → 2NaO 2

Ozonides contain ion O 3 - with the oxidation state -1/3. Obtained by the action of ozone on alkali metal hydroxides:
KOH (tv.) + O 3 → KOH 3 + KOH + O 2

And he dioxygenyl O 2 + has an oxidation state of +1/2. Received by reaction:
PtF 6 + O 2 → O 2 PtF 6

Oxygen fluorides
Oxygen difluoride, OF 2 oxidation state +2, is obtained by passing fluorine through an alkali solution:
2F 2 + 2NaOH → OF 2 + 2NaF + H 2 O

Oxygen monofluoride (Dioxyfluoride), O 2 F 2, unstable, oxidation state +1. It is obtained from a mixture of fluorine and oxygen in a glow discharge at a temperature of −196 ° C.

By passing a glow discharge through a mixture of fluorine with oxygen at a certain pressure and temperature, mixtures of higher oxygen fluorides O 3 F 2, O 4 F 2, O 5 F 2 and O 6 F 2 are obtained.
Oxygen supports the processes of respiration, combustion, and decay. In free form, the element exists in two allotropic modifications: O 2 and O 3 (ozone).

Oxygen application

The widespread industrial use of oxygen began in the middle of the 20th century, after the invention of turbo expanders - devices for liquefying and separating liquid air.

In metallurgy

The converter method of steel production is associated with the use of oxygen.

Welding and cutting metals

Oxygen in cylinders is widely used for flame cutting and welding of metals.

Rocket fuel

Liquid oxygen, hydrogen peroxide, nitric acid, and other oxygen-rich compounds are used as oxidizing agents for rocket fuel. A mixture of liquid oxygen and liquid ozone is one of the most powerful oxidizers of rocket fuel (the specific impulse of the hydrogen - ozone mixture exceeds the specific impulse for the hydrogen-fluorine and hydrogen-oxygen fluoride pair).

In medicine

Oxygen is used to enrich breathing gas mixtures in case of respiratory failure, for the treatment of asthma, in the form of oxygen cocktails, oxygen bags, etc.

In the food industry

In the food industry, oxygen is registered as a food additive E948as a propellant and packing gas.

The biological role of oxygen

Living things breathe oxygen in the air. Oxygen is widely used in medicine. In case of cardiovascular diseases, oxygen foam ("oxygen cocktail") is introduced into the stomach to improve metabolic processes. Subcutaneous administration of oxygen is used for trophic ulcers, elephantiasis, gangrene and other serious diseases. For disinfection and deodorization of air and purification of drinking water, artificial enrichment with ozone is used. The radioactive isotope of oxygen 15 O is used to study blood flow velocity and pulmonary ventilation.

Toxic oxygen derivatives

Some oxygen derivatives (so-called reactive oxygen species) such as singlet oxygen, hydrogen peroxide, superoxide, ozone and hydroxyl radicals are highly toxic products. They are formed during the activation or partial reduction of oxygen. Superoxide (superoxide radical), hydrogen peroxide and hydroxyl radical can be formed in the cells and tissues of the human and animal body and cause oxidative stress.

Oxygen isotopes

Oxygen has three stable isotopes: 16 O, 17 O and 18 O, the average content of which is, respectively, 99.759%, 0.037% and 0.204% of the total number of oxygen atoms on Earth. The sharp predominance in the mixture of isotopes of the lightest of them, 16 O, is due to the fact that the nucleus of the 16 O atom consists of 8 protons and 8 neutrons. And such nuclei, as follows from the theory of the structure of the atomic nucleus, are especially stable.

There are radioactive isotopes 11 O, 13 O, 14 O (half-life 74 sec), 15 O (T 1/2 \u003d 2.1 min), 19 O (T 1/2 \u003d 29.4 sec), 20 O (contradictory data on half-life from 10 min to 150 years).

Additional Information

Oxygen compounds
Liquid oxygen
Ozone

Oxygen, Oxygenium, O (8)
The discovery of oxygen (Oxygen, French Oxygene, German Sauerstoff) marked the beginning of the modern period in the development of chemistry. It has been known since ancient times that air is needed for combustion, but for many centuries the combustion process remained unclear. Only in the 17th century. Mayow and Boyle independently expressed the idea that the air contains a certain substance that supports combustion, but this completely rational hypothesis was not developed then, since the idea of \u200b\u200bcombustion as a process of combining a burning body with a certain component of air seemed at that time, contrary to such an obvious act as the fact that during combustion there is a decomposition of a burning body into elementary components. It was on this basis at the turn of the 17th century. arose the theory of phlogiston, created by Becher and Stahl. With the onset of the chemical-analytical period of the development of chemistry (the second half of the 18th century) and the emergence of "pneumatic chemistry" - one of the main branches of the chemical-analytical direction - combustion, as well as respiration, again attracted the attention of researchers. The discovery of various gases and the establishment of their important role in chemical processes was one of the main stimuli for the systematic studies of the combustion processes of substances undertaken by Lavoisier. Oxygen was discovered in the early 70s of the 18th century.

The first report of this discovery was made by Priestley at a meeting of the Royal Society of England in 1775. Priestley, heating red mercury oxide with a large incendiary glass, received a gas in which a candle burned more brightly than in ordinary air, and a smoldering torch flared. Priestley identified some of the properties of the new gas and called it daphlogisticated air. However, two years earlier Priestley (1772) Scheele also obtained oxygen by decomposition of mercury oxide and in other ways. Scheele called this gas Feuerluft. Scheele was able to make a message about his discovery only in 1777.

In 1775, Lavoisier appeared before the Paris Academy of Sciences with the message that he had succeeded in obtaining "the cleanest part of the air that surrounds us," and described the properties of this part of the air. Initially, Lavoisier called this "air" the base de l "air vital. The almost simultaneous discovery of oxygen by several scientists in different countries sparked disputes over priority. Priestley was particularly persistent in his recognition of himself as a pioneer. In essence, these disputes have not ended until now.A detailed study of the properties of oxygen and its role in the processes of combustion and formation of oxides led Lavoisier to the wrong conclusion that this gas is an acid-forming principle. In 1779 Lavoisier, in accordance with this conclusion introduced a new name for oxygen - the acid-forming principle (principe acidifiant ou principe oxygine) Lavoisier derived the word oxygine that appears in this complex name from the Greek - acid and “I produce”.

Ministry of Education and Science of the Russian Federation

"OXYGEN"

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General characteristics of oxygen.

OXYGEN (Latin Oxygenium), O (read "o"), chemical element with atomic number 8, atomic mass 15.9994. In Mendeleev's periodic table of elements, oxygen is located in the second period in group VIA.

Natural oxygen consists of a mixture of three stable nuclides with mass numbers 16 (dominates in the mixture, its content is 99.759% by mass), 17 (0.037%) and 18 (0.204%). The radius of the neutral oxygen atom is 0.066 nm. The configuration of the outer electron layer of a neutral unexcited oxygen atom is 2s2p4. The sequential ionization energies of the oxygen atom are 13.61819 and 35.118 eV, the electron affinity is 1.467 eV. The radius of the O 2 ion is at different coordination numbers from 0.121 nm (coordination number 2) to 0.128 nm (coordination number 8). In compounds, it exhibits the oxidation state –2 (valence II) and, less often, –1 (valence I). On the Pauling scale, the electronegativity of oxygen is 3.5 (second place among non-metals after fluorine).

Free oxygen is a colorless, odorless and tasteless gas.

Features of the structure of the O 2 molecule: atmospheric oxygen consists of diatomic molecules. The interatomic distance in the O 2 molecule is 0.12074 nm. Molecular oxygen (gaseous and liquid) is a paramagnetic substance, each O 2 molecule contains 2 unpaired electrons. This fact can be explained by the fact that there is one unpaired electron in each of the two antibonding orbitals in the molecule.

The dissociation energy of the O 2 molecule into atoms is quite high and amounts to 493.57 kJ / mol.

Physical and chemical properties

Physical and chemical properties: in free form it is found in the form of two modifications O 2 ("normal" oxygen) and O 3 (ozone). О 2 is a colorless and odorless gas. Under normal conditions, the density of oxygen gas is 1.42897 kg / m 3. The boiling point of liquid oxygen (the liquid is blue) is –182.9 ° C. At temperatures from –218.7 ° C to –229.4 ° C, there is solid oxygen with a cubic lattice (-modification), at temperatures from –229.4 ° C to –249.3 ° C - -modification with a hexagonal lattice and at temperatures below –249.3 ° C - cubic modification. Other modifications of solid oxygen were obtained at elevated pressure and low temperatures.

At 20 ° C the solubility of the O 2 gas: 3.1 ml per 100 ml of water, 22 ml per 100 ml of ethanol, 23.1 ml per 100 ml of acetone. There are organic fluorine-containing liquids (for example, perfluorobutyltetrahydrofuran) in which the oxygen solubility is much higher.

The high strength of the chemical bond between atoms in the O2 molecule leads to the fact that at room temperature, gaseous oxygen is chemically rather weakly active. In nature, it slowly enters into transformations during decay processes. In addition, oxygen at room temperature is capable of reacting with blood hemoglobin (more precisely, with heme iron II), which ensures the transfer of oxygen from the respiratory system to other organs.

Oxygen interacts with many substances without heating, for example, with alkali and alkaline earth metals (corresponding oxides such as Li 2 O, CaO, etc. are formed, peroxides such as Na 2 O2, BaO2, etc. and superoxides such as KO 2, RbO 2 etc.), causes the formation of rust on the surface of steel products. Without heating, oxygen reacts with white phosphorus, some aldehydes and other organic substances.

When heated, even a little, the reactivity of oxygen increases sharply. When ignited, it reacts with an explosion with hydrogen, methane, other flammable gases, with a large number of simple and complex substances. It is known that when heated in an oxygen atmosphere or in air, many simple and complex substances burn, and various oxides are formed, for example:

S + O 2 \u003d SO 2; C + O 2 \u003d CO 2

4Fe + 3O 2 \u003d 2Fe 2 O 3; 2Cu + O 2 \u003d 2CuO

4NH 3 + 3O 2 \u003d 2N 2 + 6H 2 O; 2H 2 S + 3O 2 \u003d 2H 2 O + 2SO 2

If a mixture of oxygen and hydrogen is stored in a glass vessel at room temperature, then the exothermic reaction of water formation

2H 2 + O 2 \u003d 2H 2 O + 571 kJ

proceeds extremely slowly; according to calculations, the first droplets of water should appear in the vessel in about a million years. But when platinum or palladium (playing the role of a catalyst) is introduced into a vessel with a mixture of these gases, as well as when ignited, the reaction proceeds with an explosion.

Oxygen reacts with nitrogen N 2 either at a high temperature (about 1500-2000 ° C), or by passing an electric discharge through a mixture of nitrogen and oxygen. Under these conditions, nitric oxide (II) is reversibly formed:

N 2 + O 2 \u003d 2NO

The resulting NO then reacts with oxygen to form brown gas (nitrogen dioxide):

2NO + О 2 \u003d 2NO2

Oxygen from non-metals does not directly interact with halogens under any conditions, from metals - with noble metals - silver, gold, platinum, etc.

Binary oxygen compounds, in which the oxidation state of oxygen atoms is –2, are called oxides (formerly called oxides). Examples of oxides: carbon monoxide (IV) CO 2, sulfur oxide (VI) SO 3, copper (I) oxide Cu 2 O, aluminum oxide Al 2 O 3, manganese (VII) oxide Mn 2 O 7.

Oxygen also forms compounds in which its oxidation state is –1. These are peroxides (the old name is peroxides), for example, hydrogen peroxide H 2 O 2, barium peroxide BaO 2, sodium peroxide Na 2 O 2 and others. These compounds contain a peroxide group - O - O -. With active alkali metals, for example, potassium, oxygen can also form superoxides, for example, KO 2 (potassium superoxide), RbO 2 (rubidium superoxide). In superoxides, the oxidation state of oxygen is –1/2. It can be noted that the superoxide formulas are often written as K 2 O 4, Rb 2 O 4, etc.

With the most active non-metal fluorine, oxygen forms compounds in positive oxidation states. So, in the compound O 2 F 2, the oxidation state of oxygen is +1, and in the compound O 2 F - +2. These compounds do not belong to oxides, but to fluorides. Oxygen fluorides can be synthesized only indirectly, for example, by acting with fluorine F 2 on dilute aqueous KOH solutions.

Discovery history

The history of the discovery of oxygen, like nitrogen, is associated with the study of atmospheric air that continued for several centuries. The Chinese alchemist Mao Hoa, and later in Europe Leonardo da Vinci, knew that air is not homogeneous by nature, but includes parts, one of which supports combustion and breathing, and the other does not. In 1665, the English naturalist R. Hooke wrote that air consists of the gas contained in nitrate, as well as of the inactive gas that makes up most of the air. The fact that air contains an element that sustains life was known to many chemists in the 18th century. The Swedish pharmacist and chemist Karl Scheele began to study the composition of air in 1768. Within three years he decomposed nitrate (KNO 3, NaNO 3) and other substances by heating and obtained "fiery air" that supported breathing and combustion. But Scheele published the results of his experiments only in 1777 in the book "Chemical Treatise on Air and Fire." In 1774, the English priest and naturalist J. Priestley, by heating "burnt mercury" (mercury oxide HgO), obtained a combustion gas. While in Paris, Priestley, who did not know that the gas he received was part of the air, reported his discovery to A. Lavoisier and other scientists. By this time, nitrogen was also discovered. In 1775 Lavoisier came to the conclusion that ordinary air consists of two gases - a gas necessary for breathing and supporting combustion, and a gas of the "opposite nature" - nitrogen. Lavoisier called the combustion gas oxygene - "forming acids" (from the Greek oxys - sour and gennao - I give birth; hence the Russian name "oxygen"), since he then believed that all acids contain oxygen. It has long been known that acids are both oxygen-containing and oxygen-free, but the name given to the Lavoisier element has remained unchanged. For almost a century and a half, 1/16 of the mass of an oxygen atom served as a unit for comparing the masses of various atoms with each other and was used to numerically characterize the masses of atoms of various elements (the so-called oxygen scale of atomic masses).

Finding in nature: oxygen is the most common element on Earth, its share (in the composition of various compounds, mainly silicates) accounts for about 47.4% of the mass of the solid earth's crust. Sea and fresh waters contain a huge amount of bound oxygen - 88.8% (by mass), in the atmosphere, the content of free oxygen is 20.95% (by volume). The element oxygen is found in more than 1500 compounds in the earth's crust.

Receiving:

At present, oxygen is obtained in industry by separating air at low temperatures. First, the air is compressed by a compressor, while the air is heated. The compressed gas is allowed to cool to room temperature and then allowed to expand freely. When expanding, the gas temperature drops sharply. The cooled air, the temperature of which is several tens of degrees below the ambient temperature, is again compressed to 10-15 MPa. Then the released heat is taken away again. After several compression-expansion cycles, the temperature drops below the boiling point of both oxygen and nitrogen. Liquid air is formed, which is then subjected to distillation (distillation). The boiling point of oxygen (–182.9 ° C) is more than 10 degrees higher than the boiling point of nitrogen (–195.8 ° C). Therefore, nitrogen evaporates from the liquid first, and oxygen accumulates in the residue. Due to slow (fractional) distillation, it is possible to obtain pure oxygen, in which the content of nitrogen impurities is less than 0.1 percent by volume.