The structure of the oxygen atom. Oxygen: chemical properties of the element

DEFINITION

Oxygen- the eighth element of the Periodic table. Refers to non-metals. It is located in the second period of the VI group A of the subgroup.

The sequence number is 8. The charge of the nucleus is +8. Atomic weight - 15.999 amu Three isotopes of oxygen occur in nature: 16 O, 17 O and 18 O, of which 16 O is the most common (99.762%).

The electronic structure of the oxygen atom

The oxygen atom has two shells, like all elements located in the second period. The group number -VI (chalcogens) - indicates that there are 6 valence electrons in the outer electronic level of the nitrogen atom. It has a high oxidizing ability (only fluorine is higher).

Rice. 1. Schematic representation of the structure of the oxygen atom.

The electronic configuration of the ground state is written as follows:

1s 2 2s 2 2p 4 .

Oxygen is an element of the p-family. The energy diagram for valence electrons in the unexcited state is as follows:

Oxygen has 2 pairs of paired electrons and two unpaired electrons. In all its compounds, oxygen exhibits valency II.

Rice. 2. Spatial image of the structure of the oxygen atom.

Examples of problem solving

EXAMPLE 1

DEFINITION

Oxygen- an element of the second period of the VIA group of the Periodic system of chemical elements D.I. Mendeleev, with atomic number 8. Symbol - O.

Atomic mass - 16 a.m.u. The oxygen molecule is diatomic and has the formula - O 2

Oxygen belongs to the p-element family. The electronic configuration of the oxygen atom is 1s 2 2s 2 2p 4 . In its compounds, oxygen is able to exhibit several oxidation states: “-2”, “-1” (in peroxides), “+2” (F 2 O). Oxygen is characterized by the manifestation of the phenomenon of allotropy - the existence in the form of several simple substances - allotropic modifications. Allotropic modifications of oxygen are oxygen O 2 and ozone O 3.

Chemical properties of oxygen

Oxygen is a strong oxidizing agent, because to complete the external electronic level he lacks only 2 electrons, and he easily attaches them. In terms of reactivity, oxygen is second only to fluorine. Oxygen forms compounds with all elements except helium, neon and argon. Oxygen directly reacts with halogens, silver, gold and platinum (their compounds are obtained indirectly). Almost all reactions involving oxygen are exothermic. Feature many reactions of combination with oxygen - the release of a large amount of heat and light. Such processes are called combustion.

Interaction of oxygen with metals. So alkali metals(except lithium) oxygen forms peroxides or superoxides, with the rest - oxides. For example:

4Li + O 2 = 2Li 2 O;

2Na + O 2 \u003d Na 2 O 2;

K + O 2 \u003d KO 2;

2Ca + O 2 \u003d 2CaO;

4Al + 3O 2 \u003d 2Al 2 O 3;

2Cu + O 2 \u003d 2CuO;

3Fe + 2O 2 \u003d Fe 3 O 4.

Interaction of oxygen with non-metals. The interaction of oxygen with non-metals proceeds when heated; all reactions are exothermic, except for the interaction with nitrogen (the reaction is endothermic, occurs at 3000C in electric arc, in nature - during a lightning discharge). For example:

4P + 5O 2 \u003d 2P 2 O 5;

C + O 2 \u003d CO 2;

2H 2 + O 2 \u003d 2H 2 O;

N 2 + O 2 ↔ 2NO - Q.

Interaction with complex inorganic substances. When complex substances are burned in an excess of oxygen, oxides of the corresponding elements are formed:

2H 2 S + 3O 2 \u003d 2SO 2 + 2H 2 O (t);

4NH 3 + 3O 2 \u003d 2N 2 + 6H 2 O (t);

4NH 3 + 5O 2 = 4NO + 6H 2 O (t, kat);

2PH 3 + 4O 2 = 2H 3 PO 4 (t);

SiH 4 + 2O 2 \u003d SiO 2 + 2H 2 O;

4FeS 2 + 11O 2 \u003d 2Fe 2 O 3 + 8 SO 2 (t).

Oxygen is able to oxidize oxides and hydroxides to compounds with a higher oxidation state:

2CO + O 2 \u003d 2CO 2 (t);

2SO 2 + O 2 = 2SO 3 (t, V 2 O 5);

2NO + O 2 \u003d 2NO 2;

4FeO + O 2 \u003d 2Fe 2 O 3 (t).

Interaction with complex organic substances. Almost all organic substances burn, being oxidized by atmospheric oxygen to carbon dioxide and water:

CH 4 + 2O 2 \u003d CO 2 + H 2 O.

In addition to combustion reactions (complete oxidation), partial or catalytic oxidation reactions are also possible, in which case the reaction products can be alcohols, aldehydes, ketones, carboxylic acids and other substances:

Oxidation of carbohydrates, proteins and fats serves as a source of energy in a living organism.

Physical properties of oxygen

Oxygen is the most abundant element on earth (47% by mass). Air contains 21% oxygen by volume. Oxygen - component water, minerals, organic matter. Plant and animal tissues contain 50-85% oxygen in the form of various compounds.

In the free state, oxygen is a colorless, tasteless and odorless gas, poorly soluble in water (3 liters of oxygen dissolve in 100 liters of water at 20C. Liquid oxygen blue color, has paramagnetic properties (is drawn into a magnetic field).

Obtaining oxygen

There are industrial and laboratory methods for producing oxygen. So, in industry, oxygen is obtained by distillation of liquid air, and the main laboratory methods for obtaining oxygen include the reactions of thermal decomposition of complex substances:

2KMnO 4 \u003d K 2 MnO 4 + MnO 2 + O 2

4K 2 Cr 2 O 7 \u003d 4K 2 CrO 4 + 2Cr 2 O 3 +3 O 2

2KNO 3 \u003d 2KNO 2 + O 2

2KClO 3 \u003d 2KCl + 3 O 2

Examples of problem solving

EXAMPLE 1

The task

The decomposition of 95 g of mercury (II) oxide produced 4.48 liters of oxygen (N.O.). Calculate the proportion of decomposed mercury (II) oxide (in wt.%).

Solution

Let us write the reaction equation for the decomposition of mercury oxide (II): 2HgO \u003d 2Hg + O 2. Knowing the volume of released oxygen, we find its amount of substance: mol. According to the reaction equation n (HgO): n (O 2) \u003d 2: 1, therefore, n (HgO) \u003d 2 × n (O 2) \u003d 0.4 mol. Let us calculate the mass of the decomposed oxide. The amount of a substance is related to the mass of the substance by the ratio: Molar mass (molecular weight of one mole) of mercury (II) oxide, calculated using the table of chemical elements of D.I. Mendeleev - 217 g/mol. Then the mass of mercury oxide (II) is equal to: m(HgO) = n(HgO) × M(HgO) \u003d 0.4 × 217 \u003d 86.8 g. Let us determine the mass fraction of the decomposed oxide:

Oxygen is in the second period of the VIth main group an outdated short version of the periodic table. According to the new numbering standards, this is the 16th group. The corresponding decision was made by IUPAC in 1988. The formula for oxygen is a simple substance- About 2. Consider its main properties, role in nature and economy. Let's start with the characteristics of the entire group of the periodic system, which is headed by oxygen. The element is different from its related chalcogens, and water is different from the hydrogen selenium and tellurium. Explanation for everyone distinctive features can be found only by learning about the structure and properties of the atom.

Chalcogens are elements related to oxygen.

Atoms with similar properties form one group in periodic system. Oxygen heads the chalcogen family, but differs from them in a number of properties.

The atomic mass of oxygen, the ancestor of the group, is 16 amu. m. Chalcogens in the formation of compounds with hydrogen and metals show their usual oxidation state: -2. For example, in the composition of water (H 2 O), the oxidation number of oxygen is -2.

The composition of typical hydrogen compounds of chalcogens corresponds to the general formula: H 2 R. When these substances are dissolved, acids are formed. Only hydrogen bond oxygen - water - has special properties. According to scientists, this unusual substance is both a very weak acid and a very weak base.

Sulfur, selenium and tellurium have typical positive oxidation states (+4, +6) in compounds with oxygen and other high electronegativity (EO) non-metals. The composition of chalcogen oxides reflect general formulas: RO 2 , RO 3 . The corresponding acids have the composition: H 2 RO 3 , H 2 RO 4 .

Elements correspond to simple substances: oxygen, sulfur, selenium, tellurium and polonium. The first three representatives exhibit non-metallic properties. The formula of oxygen is O 2. An allotropic modification of the same element is ozone (O 3). Both modifications are gases. Sulfur and selenium are solid non-metals. Tellurium is a metalloid substance, conductor electric current, polonium is a metal.

Oxygen is the most common element

We already know that there is another kind of existence of the same chemical element in the form of a simple substance. This is ozone, a gas that forms a layer at a height of about 30 km from the earth's surface, often called the ozone layer. Bound oxygen is included in water molecules, in the composition of many rocks and minerals, organic compounds.

The structure of the oxygen atom

The periodic table of Mendeleev contains complete information about oxygen:

1. The ordinal number of the element is 8.
2. Core charge - +8.
3. The total number of electrons is 8.
4. The electronic formula of oxygen is 1s 2 2s 2 2p 4 .

There are three in nature stable isotope, which have the same serial number in the periodic table, identical composition of protons and electrons, but different number neutrons. Isotopes are designated by the same symbol - O. For comparison, we present a diagram reflecting the composition of three oxygen isotopes:

Properties of oxygen - a chemical element

There are two unpaired electrons on the 2p sublevel of the atom, which explains the appearance of the oxidation states -2 and +2. The two paired electrons cannot be separated to increase the oxidation state to +4, as with sulfur and other chalcogens. The reason is the absence of a free sublevel. Therefore, in the compounds chemical element oxygen does not show a valency and oxidation state equal to the group number in short version periodic system (6). Its usual oxidation number is -2.

Only in compounds with fluorine does oxygen exhibit a positive oxidation state of +2, which is uncharacteristic for it. The EO value of two strong non-metals is different: EO(O) = 3.5; EO (F) = 4. As a more electronegative chemical element, fluorine holds its electrons more strongly and attracts valence particles to oxygen atoms. Therefore, in the reaction with fluorine, oxygen is a reducing agent, it donates electrons.

Oxygen is a simple substance

The English researcher D. Priestley in 1774, during the experiments, released gas during the decomposition of mercury oxide. Two years earlier, K. Scheele obtained the same substance in its pure form. Only a few years later, the French chemist A. Lavoisier established what kind of gas is part of the air, studied the properties. Chemical formula oxygen - O 2. Let us reflect in the recording of the composition of the substance the electrons involved in the formation of a nonpolar covalent bond- Oh:: Oh. Let's replace each bonding electron pair with one line: O=O. This oxygen formula clearly shows that the atoms in the molecule are connected between two common pairs of electrons.

Let's perform simple calculations and determine what the relative molecular weight of oxygen is: Mr (O 2) \u003d Ar (O) x 2 \u003d 16 x 2 \u003d 32. For comparison: Mr (air) \u003d 29. The chemical formula of oxygen differs from one an oxygen atom. This means that Mr (O 3) \u003d Ar (O) x 3 \u003d 48. Ozone is 1.5 times heavier than oxygen.

Physical Properties

Oxygen is a colorless, tasteless and odorless gas (at normal temperature and atmospheric pressure). The substance is slightly heavier than air; soluble in water, but in small quantities. The melting point of oxygen is negative and is -218.3 °C. The point at which liquid oxygen turns back into gaseous oxygen is its boiling point. For O 2 molecules, the value of this physical quantity reaches -182.96 °C. In the liquid and solid state, oxygen acquires a light blue color.

Obtaining oxygen in the laboratory

When oxygen-containing substances, such as potassium permanganate, are heated, colorless gas, which can be collected in a flask or test tube. If you bring a lighted torch into pure oxygen, it burns more brightly than in air. Two other laboratory methods for obtaining oxygen are the decomposition of hydrogen peroxide and potassium chlorate (berthollet salt). Consider the scheme of the device, which is used for thermal decomposition.

In a test tube or a round-bottom flask, pour a little berthollet salt, close with a stopper with a gas outlet tube. Its opposite end should be directed (under water) to the flask turned upside down. The neck should be lowered into a wide glass or crystallizer filled with water. When a test tube with Berthollet salt is heated, oxygen is released. Through the gas outlet tube, it enters the flask, displacing water from it. When the flask is filled with gas, it is closed under water with a cork and turned over. The oxygen obtained in this laboratory experiment can be used to study the chemical properties of a simple substance.

Combustion

If the laboratory is burning substances in oxygen, then you need to know and observe fire regulations. Hydrogen burns instantly in air, and mixed with oxygen in a ratio of 2:1, it is explosive. The combustion of substances in pure oxygen is much more intense than in air. This phenomenon is explained by the composition of the air. Oxygen in the atmosphere is slightly more than 1/5 of the part (21%). Combustion is the reaction of substances with oxygen, as a result of which various products are formed, mainly oxides of metals and non-metals. Mixtures of O 2 with combustible substances are flammable, in addition, the resulting compounds can be toxic.

The burning of an ordinary candle (or match) is accompanied by the formation of carbon dioxide. The following experience can be done at home. If you burn a substance under glass jar or a large glass, the combustion will stop as soon as all the oxygen is used up. Nitrogen does not support respiration and combustion. Carbon dioxide, a product of oxidation, no longer reacts with oxygen. Transparent allows you to detect the presence after the burning of the candle. If the combustion products are passed through calcium hydroxide, the solution becomes cloudy. A chemical reaction takes place between lime water and carbon dioxide, resulting in insoluble calcium carbonate.

Production of oxygen on an industrial scale

The cheapest process, which results in air-free O 2 molecules, does not involve chemical reactions. In industry, say, in metallurgical plants, air at low temperature and high pressure liquefy. Such essential components atmosphere, like nitrogen and oxygen, boil at different temperatures. Separate the air mixture while gradually heating to normal temperature. First, nitrogen molecules are released, then oxygen. The separation method is based on different physical properties of simple substances. The formula of a simple substance of oxygen is the same as it was before cooling and liquefying air - O 2.

As a result of some electrolysis reactions, oxygen is also released, it is collected over the corresponding electrode. Gas is needed by industrial and construction enterprises in large volumes. The demand for oxygen is constantly growing, especially in the chemical industry. The resulting gas is stored for industrial and medical purposes in steel cylinders provided with markings. Oxygen tanks are painted blue or cyan to distinguish them from others. liquefied gases- nitrogen, methane, ammonia.

Chemical calculations according to the formula and equations of reactions involving O 2 molecules

Numerical value molar mass oxygen coincides with another value - the relative molecular weight. Only in the first case there are units of measure. Briefly, the formula for the substance of oxygen and its molar mass should be written as follows: M (O 2) \u003d 32 g / mol. Under normal conditions, a mole of any gas corresponds to a volume of 22.4 liters. This means that 1 mol O 2 is 22.4 liters of a substance, 2 mol O 2 is 44.8 liters. According to the reaction equation between oxygen and hydrogen, it can be seen that 2 moles of hydrogen and 1 mole of oxygen interact:

If 1 mol of hydrogen is involved in the reaction, then the volume of oxygen will be 0.5 mol. 22.4 l / mol \u003d 11.2 l.

The role of O 2 molecules in nature and human life

Oxygen is consumed by living organisms on Earth and has been involved in the cycle of matter for over 3 billion years. This is the main substance for respiration and metabolism, with its help the decomposition of molecules occurs. nutrients, the energy necessary for organisms is synthesized. Oxygen is constantly consumed on Earth, but its reserves are replenished through photosynthesis. The Russian scientist K. Timiryazev believed that thanks to this process, life still exists on our planet.

The role of oxygen in nature and economy is great:

• absorbed in the process of respiration by living organisms;
• participates in photosynthesis reactions in plants;
• is part of organic molecules;
• the processes of decay, fermentation, rusting proceed with the participation of oxygen, which acts as an oxidizing agent;
• used to obtain valuable products of organic synthesis.

Liquefied oxygen in cylinders is used for cutting and welding metals at high temperatures. These processes are carried out at machine-building plants, transport and construction companies. For work under water, underground, on high altitude in airless space, people also need O 2 molecules. are used in medicine to enrich the composition of the air inhaled by sick people. Gas for medical purposes differs from technical gas in the almost complete absence of impurities and odor.

Oxygen is the ideal oxidizing agent

Oxygen compounds are known with all the chemical elements of the periodic table, except for the first representatives of the family noble gases. Many substances directly react with O atoms, except for halogens, gold and platinum. Great importance have phenomena involving oxygen, which are accompanied by the release of light and heat. Such processes are widely used in everyday life and industry. In metallurgy, the interaction of ores with oxygen is called roasting. The pre-crushed ore is mixed with oxygen enriched air. At high temperatures, metals are reduced from sulfides to simple substances. This is how iron and some non-ferrous metals are obtained. The presence of pure oxygen increases the speed technological processes in various branches of chemistry, technology and metallurgy.

The emergence of a cheap method for obtaining oxygen from air by separation into components at low temperature stimulated the development of many areas industrial production. Chemists consider O 2 molecules and O atoms to be ideal oxidizing agents. These are natural materials, they are constantly renewed in nature, do not pollute environment. Besides, chemical reactions with the participation of oxygen most often end with the synthesis of another natural and safe product - water. The role of O 2 in the neutralization of toxic industrial wastes, purification of water from pollution is great. In addition to oxygen, it is used for disinfection allotropic modification— ozone. This simple substance has a high oxidizing activity. When water is ozonized, pollutants are decomposed. Ozone also has a detrimental effect on pathogenic microflora.

OXYGEN (Latin Oxygenium), O, a chemical element of group VI of the short form (group 16 of the long form) of the periodic system, belongs to the 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. An 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 have been artificially obtained with mass numbers 12-26.

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 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(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.) and in the composition 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 diatomic molecules About 2 . 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 even number 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 of the 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 (eg 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 weakening O-O connections and to an increase in the reactivity 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, a 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 immediately burns out when ignited, some volatile organic substances are capable of self-ignition 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 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 in various substances(for example, enzymes oxidases and oxidoreductases) takes part in all oxidative processes occurring in living organisms. As a result, it stands out a large number of energy 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 the gas-flame processing of metals (see, for example, Oxy-fuel cutting), in 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 for spaceships, 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 rocket propellants, 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.

Introduction

Every day we breathe in the air we need. Have you ever thought about what, more precisely, what substances the air consists of? Most of all it contains nitrogen (78%), followed by oxygen (21%) and inert gases (1%). Although oxygen does not make up the most basic part of the air, without it the atmosphere would be uninhabitable. Thanks to him, life exists on Earth, because nitrogen, both together and individually, is detrimental to humans. Let's look at the properties of oxygen.

Physical properties of oxygen

In the air, oxygen is simply not distinguishable, since under normal conditions it is a gas without taste, color and smell. But oxygen can be artificially transferred to other states of aggregation. So, at -183 o C it becomes liquid, and at -219 o C it hardens. But solid and liquid oxygen can only be obtained by a person, and in nature it exists only in a gaseous state. looks like this (photo). And hard like ice.

The physical properties of oxygen are also the structure of the molecule of a simple substance. Oxygen atoms form two such substances: oxygen (O 2) and ozone (O 3). The model of an oxygen molecule is shown below.

Oxygen. Chemical properties

The first thing with which the chemical characteristic of an element begins is its position in the periodic system of D. I. Mendeleev. So, oxygen is in the 2nd period of the 6th group of the main subgroup at number 8. Its atomic mass is 16 amu, it is a non-metal.

IN inorganic chemistry its binary compounds with other elements were combined into a separate one - oxides. oxygen can form chemical compounds both metals and non-metals.

Let's talk about getting it in the laboratories.

Chemically, oxygen can be obtained by decomposing potassium permanganate, hydrogen peroxide, bartolet salt, nitrates active metals and heavy metal oxides. Consider the reaction equations for each of these methods.

1. Water electrolysis:

H 2 O 2 \u003d H 2 O + O 2

5. Decomposition of heavy metal oxides (eg mercury oxide):

2HgO \u003d 2Hg + O 2

6. Decomposition of nitrates of active metals (for example, sodium nitrate):

2NaNO 3 \u003d 2NaNO 2 + O 2

Application of oxygen

We are done with chemical properties. Now it's time to talk about the use of oxygen in human life. It is needed for fuel combustion in electrical and thermal power plants. It is used to produce steel from cast iron and scrap metal, for welding and cutting metal. Oxygen is needed for firefighters' masks, divers' cylinders, is used in ferrous and non-ferrous metallurgy, and even in the manufacture of explosives. also in Food Industry oxygen is known as food additive E948. It seems that there is no industry where it is not used, but it plays the most important role in medicine. There he is called "medical oxygen". In order for oxygen to be usable, it is pre-compressed. The physical properties of oxygen contribute to the fact that it can be compressed. In this form, it is stored inside cylinders similar to these.

It is used in intensive care and in operations in equipment to maintain life processes in the body of a sick patient, as well as in the treatment of certain diseases: decompression, pathologies gastrointestinal tract. With its help, doctors save many lives every day. Chemical and physical properties oxygen contribute to the fact that it is used so widely.