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 on the 2nd energy level, which has only s- and p-orbitals. This excludes the possibility of the transition of O atoms to an excited state, therefore oxygen in all compounds exhibits a constant valency equal to II. Having a high electronegativity, oxygen atoms are always negatively charged in compounds (s.o. = -2 or -1). The exception is OF 2 and O 2 F 2 fluorides.

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

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 predominates). Oxygen is part of the atmosphere (20.9% by volume, 23.2% by mass), 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 plant and animal tissues, 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 slightly soluble in water - 5 volumes in 100 volumes of water. However, if all the oxygen dissolved in water passed into the atmosphere, then it would occupy a huge volume - 10 million km 3 (n.c.). This is equal to approximately 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 saltpeter heating, 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.

The structure of the ozone molecule

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 - colorless, odorless and tasteless gas, m.p. –218.7 °С, b.p. -182.96 °C, paramagnetic.

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

Obtaining oxygen

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

2H 2 O → 2H 2 + O 2

2. In the laboratory, oxygen is produced by:
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 salt KClO 3:
2KClO 3 \u003d 2KCl + 3O 2 (MnO 2 catalyst)

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. Decomposition of hydrogen peroxide:
2H 2 O 2 \u003d H 2 O + O 2 (MnO 2 catalyst)

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

On the 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

Total:
2K 2 O 4 + 2CO 2 \u003d 2K 2 CO 3 + 3O 2

When K 2 O 2 is used, 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 (i.e. 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. Burning - b a rapid process of oxidation of a substance, accompanied by the release of a large amount of heat and light. To prove that the flask contains oxygen, and not some other gas, it is necessary to lower a smoldering splinter into the flask. In oxygen, a smoldering splinter flares brightly. The combustion of various substances in air is a redox process in which oxygen is the oxidizing agent. Oxidizing agents are substances that “take away” electrons from reducing substances. The good oxidizing properties of oxygen can be easily explained by the structure of its outer electron shell.

The valence shell of oxygen 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 before the octet, which oxygen seeks to accept from the electron shells of other elements, entering into reactions with them as an oxidizing agent.

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

So, oxygen is the second most powerful oxidizing agent among all the elements of the Periodic Table. Most of its most important chemical properties are related to 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 (the so-called pyrophoric iron) spontaneously ignites in air, forming Fe 2 O 3, and 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

With non-metals (sulfur, graphite, hydrogen, phosphorus, etc.), oxygen reacts 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 a temperature above 1200 o C or in an electrical discharge.

Oxygen is able to oxidize 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.

Compounds containing the dioxygenyl cation O 2 + are known, 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 active than oxygen O 2 . So, ozone oxidizes iodide - ions I - in a solution of Kl:

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, acts as a protector of all life on Earth from the harmful ultraviolet radiation of the sun. The thin ozone layer absorbs this radiation, and it does not reach the Earth's surface. There are significant fluctuations in the thickness and extent of this layer over time (the so-called ozone holes), the reasons for such fluctuations have not yet been elucidated.

Application of oxygen O 2: to intensify the processes of producing iron and steel, in the smelting of 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, in welding and cutting metals.

The use of ozone O 3: for disinfection drinking water, Wastewater, air, for bleaching fabrics.

OXYGEN (Latin Oxygenium), Oh, chemical element Group VI of the short form (group 16 of the long form) of the periodic system, refers to chalcogens; 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 16 O isotopes in the mixture is due to the fact that the nucleus of the 16 O atom consists of 8 protons and 8 neutrons. equal number 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 are artificially obtained.

History reference. Oxygen was obtained independently in 1774 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 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 that contain oxygen. Among them, minerals formed by salts of oxygen-containing acids predominate (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 hydroxides and rocks. rocks (for example, basalt). Molecular oxygen makes up 20.95% by volume (23.10% by mass) of the earth's atmosphere. Atmospheric oxygen 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.) inorganic compounds skeleton.

Properties. The structure of the outer electron shell of the oxygen atom 2s 2 2p 4; in compounds it shows 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, consisting of triatomic O 3 molecules.

In the ground state, the oxygen atom has an even number of valence electrons, two of which are unpaired. Therefore, oxygen, which does not have a low-energy vacant d-opbital, is bivalent in most chemical compounds. Depending on the nature chemical bond and the type of 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 (eg Be and Zn oxoacetates), 6 (eg MgO, CdO), 8 (eg 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, and phosphorus. Therefore, for oxygen, one double bond (494 kJ/mol) is energetically more favorable than two simple bonds (146 kJ/mol).

The paramagnetism of O 2 molecules is explained by the presence of two unpaired electrons with parallel spins in doubly degenerate antibonding π* orbitals. Since there are four electrons more in the bonding orbitals of the molecule than in the loosening orbitals, the bond order in O 2 is 2, i.e., the bond between the oxygen atoms is double. If, under a photochemical or chemical action, two electrons with opposite spins appear on the same π * orbital, the first excited state arises, located 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 that of the ground state. Excitation is accompanied by an increase in interatomic O-O 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 an increase in the chemical activity of oxygen. Both excited states of the O 2 molecule play an important role in the oxidation reactions in the gas phase.

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

Oxygen is highly reactive, strong oxidizing agent: interacts with most simple substances under normal conditions, mainly with the formation of the corresponding oxides (many reactions that proceed slowly at room temperature or more low temperatures, when heated, are accompanied by an explosion and the release of a large amount of heat). Oxygen interacts under normal conditions with hydrogen (water H 2 O is formed; mixtures of oxygen with hydrogen are explosive - see Detonating 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 metals (mainly metal peroxides and superoxides, such as 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: cotton wool impregnated with it instantly burns out when ignited, some volatile organic matter capable of self-igniting when they are at a distance of several meters from 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 O 2), O 2- - oxides (oxidation state of the oxygen atom -2). Positive oxidation states +1 and +2 oxygen exhibits in fluorides О 2 F 2 and OF 2, respectively. Oxygen fluorides are unstable, they are strong oxidizing agents and fluorinating reagents.

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

Biological role . Oxygen, both in free form and as part of various substances (for example, oxidase and oxidoreductase enzymes), takes part in all oxidative processes occurring in living organisms. As a result, a large amount of energy is expended in the process of life.

Receipt. 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), by 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 tank tanks.

Application. Technical oxygen is used as an oxidizing agent in metallurgy (see, for example, the Oxygen-converter process), in gas-flame processing of metals (see, for example, Oxygen cutting), in the chemical industry in the production of artificial liquid fuels, lubricating oils, nitric and sulfuric acids, methanol, ammonia and ammonia fertilizers, metal peroxides, etc. Pure oxygen is used in oxygen-breathing apparatus on space ships, submarines, when climbing to high altitudes, carrying out underwater work, in medicinal purposes in medicine (see the article Oxygen Therapy). Liquid oxygen is used as an oxidizing agent for rocket fuels, during blasting. Aqueous emulsions of solutions of gaseous oxygen in some organofluorine solvents are 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 is a chemical element whose properties will be discussed in the next few paragraphs. Let us turn to the Periodic System of chemical elements of D.I. Mendeleev. The element oxygen is located in period 2, group VI, the main subgroup.

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

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

The valency of oxygen in most compounds is II. An oxygen atom can attach two electrons and turn into an ion: O0 + 2ē = O−2.

It is worth noting that oxygen is the most common element on our planet. Oxygen is part of the water. Marine and fresh water 89% by mass are composed of oxygen. Oxygen is found in many minerals and rocks. The mass fraction of oxygen in the earth's crust is about 47%. Air contains about 23% oxygen by mass.

Physical properties of oxygen

When two oxygen atoms interact, a stable molecule of a simple oxygen substance O2 is formed. This simple substance, like the element, is called oxygen. Do not confuse oxygen as an element and oxygen as a simple substance!

The physical properties of oxygen It is 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 mass) 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. Gaseous oxygen 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 strongly cooled. So, at a temperature -183°C oxygen condenses into a clear mobile liquid of a pale blue 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 raised, then -218°С, solid oxygen will begin to melt, and when -183°C- boil. Therefore, the boiling and condensation points, as well as the freezing and melting points for substances, are the same.

Dewar vessels are used to store and transport liquid oxygen.. Dewar vessels are used for storage and transportation of liquids, the temperature of which must remain constant for a long time. The Dewar vessel bears the name of its inventor, the Scottish physicist and chemist James Dewar.

The simplest Dewar vessel is a household thermos. The device 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 for a long time does not cool down or heat up.

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

In nature, there is another simple substance, consisting of oxygen atoms. This is ozone. Chemical formula ozone O3. Ozone, like oxygen, normal conditions- gas. Ozone is formed 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 sharp bad smell. Ozone is obtained in the laboratory in special devices - ozonators. Ozonizer- a glass tube into which a current of oxygen is supplied, and an electric discharge is created. An electrical discharge turns oxygen into ozone:

Unlike colorless oxygen, ozone is a blue gas. The solubility of ozone in water is about 0.5 liters of gas per 1 liter of water, which is much higher than that of oxygen. Given this property, ozone is used to disinfect drinking water, as it has a detrimental effect on pathogens.

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

Thus, we can conclude that 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

Means, oxygen and ozone allotropic modifications 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.

The oxygen cycle in nature

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

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

CO2 + H2O → C6H12O6 + O2.

Oxygen can be formed in upper layers Earth's atmosphere: due to the impact solar radiation, water vapor partially decomposes with the formation of oxygen.

Oxygen is consumed during respiration, fuel combustion, oxidation of various substances in living organisms, and oxidation of inorganic substances found in nature. A large amount of oxygen is consumed in technological processes such as, for example, steel smelting.

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

• Oxygen- an element of group VI, the main subgroup, 2 periods of the Periodic System of 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 gas, odorless, tasteless, practically insoluble in water, at a temperature of -183 ° C it condenses into a pale blue liquid. At -218°C crystallizes in the form of blue crystals
• Ozone- a blue gas with a pungent odor. Let's well dissolve in water. At -112°С, it condenses into a violet liquid, crystallizes as dark violet, almost black crystals, at -197°С
• Liquid oxygen, ozone and other gases are stored in Dewar flasks

Oxygen formsperoxides with an oxidation state of −1.
- For example, peroxides are obtained by burning alkali metals in oxygen:
2Na + O 2 → Na 2 O 2

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

- According to the principles of combustion developed by A. N. Bach and K. O. Engler, oxidation occurs in two stages with the formation of an intermediate peroxide compound. This intermediate compound 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 (O 2 - ion). Obtained by the interaction of peroxides with oxygen at elevated pressures and temperatures:
Na 2 O 2 + O 2 → 2NaO 2

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

And he dioxygenyl O 2 + has an oxidation state of +1/2. Get 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 (Dioxydifluoride), O 2 F 2 , unstable, oxidation state +1. Obtained from a mixture of fluorine and oxygen in a glow discharge at a temperature of -196 ° C.

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 its free form, the element exists in two allotropic modifications: O 2 and O 3 (ozone).

Application of oxygen

The widespread industrial use of oxygen began in the middle of the 20th century, after the invention of turboexpanders - 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 of 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 an oxidizing agent for rocket fuel. A mixture of liquid oxygen and liquid ozone is one of the most powerful rocket fuel oxidizing agents (the specific impulse of a hydrogen-ozone mixture exceeds the specific impulse for a hydrogen-fluorine and hydrogen-oxygen fluoride pair).

In medicine

Oxygen is used to enrich respiratory gas mixtures in case of respiratory failure, to treat asthma, in the form of oxygen cocktails, oxygen pillows, etc.

In the food industry

V Food Industry oxygen is registered as a food additive E948, as propellant and packaging gas.

The biological role of oxygen

Living beings breathe oxygen in the air. Oxygen is widely used in medicine. In cardiovascular diseases, to improve metabolic processes, oxygen foam (“oxygen cocktail”) is introduced into the stomach. Subcutaneous administration of oxygen is used for trophic ulcers, elephantiasis, gangrene and others. serious illnesses. Artificial enrichment with ozone is used to disinfect and deodorize the air and purify drinking water. The radioactive isotope of oxygen 15 O is used to study the rate of blood flow, pulmonary ventilation.

Toxic oxygen derivatives

Some oxygen derivatives (so-called reactive oxygen species), such as singlet oxygen, hydrogen peroxide, superoxide, ozone, and the hydroxyl radical, are highly toxic products. They are formed in the process of 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.

Isotopes of oxygen

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 of the lightest of them, 16 O, in the mixture of isotopes 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, have a special stability.

There are radioactive isotopes 11 O, 13 O, 14 O (half-life 74 sec), 15 O (T 1/2 = 2.1 min), 19 O (T 1/2 = 29.4 sec), 20 O (controversial half-life data from 10 minutes 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. Since ancient times, it has been known that air is needed for combustion, but for many centuries the combustion process remained incomprehensible. Only in the XVII century. Mayow and Boyle, independently of each other, expressed the idea that the air contains some substance that supports combustion, but this completely rational hypothesis was not developed at that time, since the concept of combustion as a process of connecting a burning body with a certain integral part air, seemed at that time contrary to such an obvious act as the fact that during combustion the decomposition of a burning body into elementary components takes place. It is on this basis at the turn of the XVII century. the theory of phlogiston, created by Becher and Stahl, arose. With the advent of the chemical-analytical period in 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 field—combustion, as well as respiration, again attracted the attention of researchers. The discovery of various gases and the establishment of them important role v chemical processes was one of the main stimuli for 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 English Royal Society in 1775. Priestley, heating red mercury oxide with a large burning glass, obtained a gas in which the candle burned more brightly than in ordinary air, and the smoldering torch flashed. Priestley determined some of the properties of the new gas and called it daphlogisticated air. However, two years earlier, Priestley (1772) Scheele also received oxygen by decomposition of mercury oxide and other methods. Scheele called this gas fiery air (Feuerluft). Scheele was able to make a report on his discovery only in 1777.

In 1775, Lavoisier reported to the Paris Academy of Sciences that he had succeeded in obtaining "the purest part of the air that surrounds us" and described the properties of this part of the air. At first, Lavoisier called this "air" an empirical, vital (Air empireal, Air vital) base of vital air (Base de l "air vital). The almost simultaneous discovery of oxygen by several scientists in different countries caused disputes over priority. Priestley was especially persistent in acknowledging himself as a discoverer. In essence, these disputes have not ended so far. A detailed study of the properties of oxygen and its role in the processes of combustion and the 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). The word oxygine appearing in this complex name was derived by Lavoisier 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 (lat. Oxygenium), O (read "o"), a chemical element with atomic number 8, atomic mass 15.9994. V periodic system elements of Mendeleev 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, it 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 the neutral unexcited oxygen atom is 2s2р4. The energies of sequential ionization 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 an oxidation state of -2 (valency II) and, less commonly, -1 (valency I). According to the Pauling scale, the electronegativity of oxygen is 3.5 (second place among non-metals after fluorine).

In its free form, 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 has 2 unpaired electrons. This fact can be explained by the fact that each of the two antibonding orbitals in the molecule contains one unpaired electron.

The energy of dissociation 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 occurs in the form of two modifications of O 2 (“ordinary” oxygen) and O 3 (ozone). O 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 - a modification with a hexagonal lattice and at temperatures below -249.3 ° C - cubic - modification. At high blood pressure and low temperatures, other modifications of solid oxygen have also been obtained.

At 20°C, the solubility of gas O 2 is: 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 solubility of oxygen is much higher.

The high strength of the chemical bond between the atoms in the O2 molecule leads to the fact that at room temperature gaseous oxygen is rather inactive chemically. In nature, it slowly enters into transformations during the processes of decay. In addition, oxygen at room temperature is able to react 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., peroxides such as Na 2 O2, BaO 2, etc. and superoxides such as KO 2, RbO 2 are formed). etc.), causes rust formation on the surface steel products. Without heating, oxygen reacts with white phosphorus, with some aldehydes and other organic substances.

When heated, even a little, the chemical activity of oxygen increases dramatically. When ignited, it reacts explosively with hydrogen, methane, other combustible gases, a large number simple and complex substances. It is known that when heated in an oxygen atmosphere or in air, many simple and complex substances burn out, 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 = 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; by calculation, the first droplets of water should appear in the vessel in about a million years. But when platinum or palladium (which play 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.

With nitrogen N 2, oxygen reacts either with 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 a brown gas (nitrogen dioxide):

2NO + O 2 = 2NO2

From non-metals, oxygen under no circumstances directly interacts with halogens, from metals - with noble metals - silver, gold, platinum, etc.

Binary compounds of oxygen, in which the oxidation state of oxygen atoms is -2, are called oxides (the former name is oxides). Examples of oxides: carbon monoxide (IV) CO 2, sulfur oxide (VI) SO 3, copper oxide (I) Cu 2 O, aluminum oxide Al 2 O 3, manganese oxide (VII) 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, with 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 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 degrees oxidation. So, in the O 2 F 2 compound, the oxidation state of oxygen is +1, and in the O 2 F compound - +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 solutions CON.

Discovery history

The history of the discovery of oxygen, like nitrogen, is connected with the study of atmospheric air that lasted several centuries. The fact that air is not homogeneous in nature, but includes parts, one of which supports combustion and breathing, and the other does not, was known back in the 8th century by the Chinese alchemist Mao Hoa, and later in Europe by Leonardo da Vinci. In 1665, the English naturalist R. Hooke wrote that air consists of a gas contained in saltpeter, as well as an inactive gas, which makes up most of the air. The fact that air contains an element that supports 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. For three years, he decomposed saltpeter (KNO 3 , NaNO 3) and other substances by heating and received "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 obtained a combustion-supporting gas by heating "burnt mercury" (mercury oxide HgO). 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 an "opposite nature" - nitrogen. Lavoisier called the combustion-supporting 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 can be both oxygen-containing and anoxic, but the name given to the element by Lavoisier 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 in the numerical characterization of the masses of atoms various elements(the so-called oxygen scale of atomic masses).

Occurrence in nature: oxygen is the most common element on Earth, its share (as part 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 part of more than 1500 compounds of the earth's crust.

Receipt:

Currently, oxygen in industry is obtained by air separation at low temperatures. First, the air is compressed by the compressor, while the air is heated. The compressed gas is allowed to cool to room temperature, and then provide its free expansion. As the gas expands, the temperature drops sharply. Cooled air, the temperature of which is several tens of degrees lower than the temperature environment, again subjected to compression up to 10-15 MPa. Then the released heat is again taken away. After several cycles of "compression-expansion" 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 first from the liquid, and oxygen accumulates in the remainder. Due to the slow (fractional) distillation, it is possible to obtain pure oxygen, in which the nitrogen impurity content is less than 0.1 volume percent.