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OXYGEN,O (oxygenium), a chemical element of the VIA subgroup of the periodic system of elements: O, S, Se, Te, Po - a member of the chalcogen family. This is the most common element in nature, its content in the Earth’s atmosphere is 21% (vol.), In the earth’s crust in the form of compounds of approx. 50% (mass.) And in the hydrosphere 88.8% (mass.).

Oxygen is necessary for the existence of life on earth: animals and plants consume oxygen in the process of respiration, and plants emit oxygen in the process of photosynthesis. Living matter contains bound oxygen not only in body fluids (in blood cells, etc.), but also in carbohydrates (sugar, cellulose, starch, glycogen), fats and proteins. Clays, rocks are composed of silicates and other oxygen-containing inorganic compounds, such as oxides, hydroxides, carbonates, sulfates and nitrates.

History reference.

The first information about oxygen became known in Europe from Chinese manuscripts of the 8th century. At the beginning of the 16th century Leonardo da Vinci published data related to oxygen chemistry, not knowing yet that oxygen is an element. Oxygen addition reactions are described in the scientific works of S. Gales (1731) and P. Bayen (1774). The studies of K. Scheele in 1771–1773 of the interaction of metals and phosphorus with oxygen deserve special attention. J. Prestley reported the discovery of oxygen as an element in 1774, a few months after Bayen reported on reactions with air. The name oxygenium ("oxygen") was given to this element shortly after its discovery by Priestley and comes from the Greek words for "giving birth to acid"; this is due to the misconception that oxygen is present in all acids. An explanation of the role of oxygen in the processes of respiration and combustion, however, belongs to A. Lavoisier (1777).

The structure of the atom.

Any natural oxygen atom contains 8 protons in the nucleus, but the number of neutrons can be 8, 9 or 10. The most common of the three oxygen isotopes (99.76%) is 16 8 O (8 protons and 8 neutrons). The content of another isotope, 18 8 O (8 protons and 10 neutrons), is only 0.2%. This isotope is used as a label or for the identification of certain molecules, as well as for biochemical and medico-chemical studies (a method for studying non-radioactive traces). The third non-radioactive oxygen isotope 17 8 O (0.04%) contains 9 neutrons and has a mass number of 17. After the mass of the carbon isotope 12 6 C was accepted by the International Commission for standard atomic mass in 1961, the weighted average atomic mass of oxygen became 15, 9994. Until 1961, the standard unit of atomic mass, chemists considered the atomic mass of oxygen, adopted for a mixture of three natural oxygen isotopes of 16,000. Physicists took the mass number of the oxygen isotope 16 8 O as the standard unit of atomic mass; therefore, on the physical scale, the average atomic mass of oxygen was 16.0044.

There are 8 electrons in an oxygen atom, while 2 electrons are on the internal level, and 6 electrons are on the external. Therefore, in chemical reactions, oxygen can take from donors to two electrons, building up its outer shell up to 8 electrons and forming an excess negative charge.

Molecular oxygen.

Like most other elements, whose atoms lack 1–2 electrons to complete the outer shell of 8 electrons, oxygen forms a diatomic molecule. In this process, a lot of energy is released (~ 490 kJ / mol) and, accordingly, the same amount of energy must be spent for the reverse process of dissociation of a molecule into atoms. The O – O bond strength is so high that at 2300 ° C only 1% of oxygen molecules dissociate into atoms. (It is noteworthy that when the nitrogen molecule N 2 is formed, the strength of the N – N bond is even higher, ~ 710 kJ / mol.)

Electronic structure.

As you might expect, the distribution of electrons by an octet around each atom is not realized in the electronic structure of the oxygen, but there are unpaired electrons, and oxygen exhibits properties typical of such a structure (for example, it interacts with a magnetic field, being a paramagnet).

Reactions.

Under appropriate conditions, molecular oxygen reacts with almost any element except noble gases. However, under room conditions, only the most active elements react with oxygen quickly enough. Probably, most reactions proceed only after dissociation of oxygen into atoms, and dissociation occurs only at very high temperatures. However, catalysts or other substances in the reacting system can promote O 2 dissociation. It is known that alkaline (Li, Na, K) and alkaline earth (Ca, Sr, Ba) metals react with molecular oxygen to form peroxides:

Receiving and application.

Due to the presence of free oxygen in the atmosphere, the most effective method for its extraction is to liquefy the air, from which impurities, CO 2, dust, etc. are removed. chemical and physical methods. The cyclic process involves compression, cooling and expansion, which leads to liquefaction of the air. When the temperature rises slowly (fractional distillation method), noble gases (the most difficult to liquefy) are evaporated from the liquid air, then nitrogen and liquid oxygen remain. As a result, liquid oxygen contains traces of noble gases and a relatively large percentage of nitrogen. For many applications, these impurities do not interfere. However, to obtain high purity oxygen, the distillation process must be repeated. Oxygen is stored in tanks and cylinders. It is used in large quantities as an oxidizing agent for kerosene and other fuels in rockets and spacecraft. The steel industry consumes gaseous oxygen to blow through the molten iron according to the Bessemer method for quickly and efficiently removing impurities C, S and P. Steel with oxygen blasting is faster and better than with air. Oxygen is also used for welding and cutting metals (oxygen-acetylene flame). Oxygen is also used in medicine, for example, to enrich the respiratory environment of patients with difficulty breathing. Oxygen can be obtained by various chemical methods, and some of them are used to obtain small amounts of pure oxygen in laboratory practice.

Electrolysis.

One of the methods for producing oxygen is the electrolysis of water containing small additives of NaOH or H 2 SO 4 as a catalyst: 2H 2 O ® 2H 2 + O 2. In this case, small impurities of hydrogen are formed. Using a discharge device, traces of hydrogen in the gas mixture are again converted into water, the vapors of which are removed by freezing or adsorption.

Thermal dissociation.

An important laboratory method for producing oxygen proposed by J. Prestley is the thermal decomposition of heavy metal oxides: 2HgO ® 2Hg + O 2. Priestley for this focused the sun's rays on mercury oxide powder. A well-known laboratory method is also the thermal dissociation of oxosalts, for example potassium chlorate in the presence of a catalyst - manganese dioxide:

Manganese dioxide, added in small quantities before calcination, allows you to maintain the required temperature and dissociation rate, and MnO 2 itself does not change in the process.

Thermal decomposition of nitrates is also used:

as well as peroxides of certain active metals, for example:

2BaO 2 ® 2BaO + O 2

The latter method was at one time widely used to extract oxygen from the atmosphere and consisted in heating BaO in air until BaO 2 was formed, followed by thermal decomposition of peroxide. The method of thermal decomposition retains its importance for the production of hydrogen peroxide.

SOME PHYSICAL PROPERTIES OF OXYGEN
Atomic number	8
Atomic mass	15,9994
Melting point, ° С	–218,4
Boiling point, ° С	–183,0
Density
solid, g / cm 3 (at t   pl)	1,27
liquid g / cm 3 (at t   bale)	1,14
gaseous, g / dm 3 (at 0 ° С)	1,429
relative air	1,105
critical a, g / cm 3	0,430
Critical temperature a, ° С	–118,8
Critical pressure a, atm	49,7
Solubility, cm 3/100 ml of solvent
in water (0 ° C)	4,89
in water (100 ° C)	1,7
in alcohol (25 ° C)	2,78
Radius, Å	0,74
covalent	0,66
ionic (O 2–)	1,40
Ionization potential, V
the first	13,614
second	35,146
Electronegativity (F \u003d 4)	3,5
a Temperature and pressure at which the density of gas and liquid are the same.

Physical properties.

Under normal conditions, oxygen is a colorless, odorless and tasteless gas. Liquid oxygen has a pale blue color. Solid oxygen exists in at least three crystalline modifications. Gaseous oxygen is soluble in water and probably forms weak compounds such as O 2 H 2 O, and possibly O 2 H 2H 2 O.

Chemical properties.

As already mentioned, the chemical activity of oxygen is determined by its ability to dissociate into O atoms, which are characterized by high reactivity. Only the most active metals and minerals react with O 2 at high speed at low temperatures. The most active alkaline (IA subgroups) and some alkaline earth (IIA subgroups) metals form peroxides of the type NaO 2 and BaO 2 with O 2. Other elements and compounds react only with the product of dissociation O 2. Under suitable conditions, all elements, with the exception of noble gases and metals Pt, Ag, Au, react with oxygen. These metals also form oxides, but under special conditions.

The electronic structure of oxygen (1s 2 2s 2 2p 4) is such that the O atom takes two electrons to the external level to form a stable external electron shell, forming the O 2– ion. In alkali metal oxides, a predominantly ionic bond is formed. It can be assumed that the electrons of these metals are almost entirely drawn to oxygen. In oxides of less active metals and nonmetals, the electron transition is incomplete, and the negative charge density on oxygen is less pronounced, therefore, the bond is less ionic or more covalent.

During the oxidation of metals by oxygen, heat is released, the value of which correlates with the strength of the M – O bond. During the oxidation of some non-metals, heat is absorbed, which indicates their less strong bonds with oxygen. Such oxides are thermally unstable (or less stable than ion-bonded oxides) and are often highly reactive. The table shows for comparison the values \u200b\u200bof the enthalpy of formation of oxides of the most typical metals, transition metals and nonmetals, elements of A- and B-subgroups (minus sign indicates heat generation).

On the properties of oxides, several general conclusions can be made:

1. The melting points of alkali metal oxides decrease with increasing atomic radius of the metal; So, t   pl (Cs 2 O) t pl (Na 2 O). Oxides in which the ionic bond predominates have higher melting points than the melting points of covalent oxides: t   pl (Na 2 O)\u003e t   pl (SO 2).

2. Oxides of chemically active metals (IA – IIIA subgroups) are more thermally stable than oxides of transition metals and nonmetals. Oxides of heavy metals in the highest oxidation state during thermal dissociation form oxides with lower oxidation states (for example, 2Hg 2+ O ® (Hg +) 2 O + 0,5O 2 ® 2Hg 0 + O 2). Such oxides in high oxidation states can be good oxidizing agents.

3. The most active metals interact with molecular oxygen at elevated temperatures to form peroxides:

Sr + O 2 ® SrO 2.

4. The oxides of active metals form colorless solutions, while the oxides of most transition metals are colored and practically insoluble. Aqueous solutions of metal oxides exhibit basic properties and are OH-containing hydroxides, while non-metal oxides in aqueous solutions form acids containing an H + ion.

5. Metals and nonmetals of A-subgroups form oxides with an oxidation state corresponding to the group number, for example, Na, Be and B form Na 1 2 O, Be II O and B 2 III O 3, and nonmetals IVA – VIIA of subgroups C, N , S, Cl form C IV O 2, NV 2 O 5, S VI O 3, Cl VII 2 O 7. The element group number only correlates with the maximum oxidation state, since oxides are also possible with lower oxidation states of the elements. In the combustion processes of compounds, typical products are oxides, for example:

2H 2 S + 3O 2 ® 2SO 2 + 2H 2 O

Carbon-containing substances and hydrocarbons, when lightly heated, oxidize (burn) to CO 2 and H 2 O. Examples of such substances are fuels - wood, oil, alcohols (as well as carbon - coal, coke and charcoal). The heat from the combustion process is utilized for the production of steam (and then electricity or goes to power plants), as well as for heating homes. Typical equations for combustion processes are as follows:

a) wood (cellulose):

(C 6 H 10 O 5)   n + 6nO 2 ® 6 nCO 2 + 5 nH 2 O + thermal energy

b) oil or gas (gasoline C 8 H 18 or natural gas CH 4):

2C 8 H 18 + 25O 2 ® 16CO 2 + 18H 2 O + thermal energy

CH 4 + 2O 2 ® CO 2 + 2H 2 O + thermal energy

C 2 H 5 OH + 3O 2 ® 2CO 2 + 3H 2 O + thermal energy

d) carbon (coal or charcoal, coke):

2C + O 2 ® 2CO + thermal energy

2CO + O 2 ® 2CO 2 + thermal energy

A number of C-, H-, N-, O-containing compounds with a high energy reserve are also subject to combustion. Oxygen for oxidation can be used not only from the atmosphere (as in previous reactions), but also from the substance itself. To initiate the reaction, a small activation of the reaction, for example, shock or shake, is sufficient. In these reactions, oxides are also combustion products, but all of them are gaseous and expand rapidly at a high final process temperature. Therefore, such substances are explosive. Examples of explosives are trinitroglycerin (or nitroglycerin) C 3 H 5 (NO 3) 3 and trinitrotoluene (or TNT) C 7 H 5 (NO 2) 3.

Oxides of metals or nonmetals with lower oxidation states of an element react with oxygen to form oxides of high oxidation states of this element:

Natural oxides obtained from ores or synthesized serve as raw materials for the production of many important metals, for example, iron from Fe 2 O 3 (hematite) and Fe 3 O 4 (magnetite), aluminum from Al 2 O 3 (alumina), magnesium from MgO (magnesia). Light metal oxides are used in the chemical industry to produce alkalis or bases. Potassium peroxide KO 2 is of unusual use, since it releases oxygen in the presence of moisture and as a result of reaction with it. Therefore, KO 2 is used in respirators to produce oxygen. Moisture from the exhaled air releases oxygen in the respirator, and KOH absorbs CO 2. Obtaining CaO and calcium hydroxide Ca (OH) 2 is a large-tonnage production in ceramic and cement technology.

Water (hydrogen oxide).

The importance of H 2 O water both in laboratory practice for chemical reactions and in vital processes requires special consideration of this substance WATER, ICE AND STEAM). As already mentioned, in the direct interaction of oxygen and hydrogen under conditions, for example, of a spark discharge, an explosion and the formation of water occur, and 143 kJ / (mol of H 2 O) is released.

The water molecule has an almost tetrahedral structure, the H – O – H angle is 104 ° 30ў. The bonds in the molecule are partially ionic (30%) and partially covalent with a high density of negative charge in oxygen and, accordingly, positive charges in hydrogen:

Due to the high strength of H – O bonds, hydrogen is difficult to split off from oxygen and water exhibits very weak acidic properties. Many properties of water are determined by the distribution of charges. For example, a water molecule forms a hydrate with a metal ion:

Water gives one electron pair to an acceptor, which can be H +:

Oxoanions and oxocations

- oxygen-containing particles having a residual negative (oxoanions) or residual positive (oxocations) charge. The O 2– ion has a high affinity (high reactivity) for positively charged H + particles. The simplest representative of stable oxoanions is hydroxide ion OH -. This explains the instability of atoms with a high charge density and their partial stabilization as a result of the addition of a particle with a positive charge. Therefore, under the action of the active metal (or its oxide) on water, OH - is formed, and not O 2–:

2Na + 2H 2 O ® 2Na + + 2OH - + H 2

Na 2 O + H 2 O ® 2Na + + 2OH -

More complex oxoanions are formed from oxygen with a metal ion or non-metallic particle that has a large positive charge, resulting in a low-charged particle with greater stability, for example:

  ° С a dark purple solid phase is formed. Liquid ozone is slightly soluble in liquid oxygen, and 49 cm 3 O 3 dissolves in 100 g of water at 0 ° C. By its chemical properties, ozone is much more active than oxygen and by its oxidizing properties it is second only to O, F 2 and OF 2 (oxygen difluoride). In ordinary oxidation, oxide and molecular oxygen O 2 are formed. Under the action of ozone on active metals, under special conditions, ozonides of the composition K + O 3 - are formed. Ozone is obtained in industry for special purposes, it is a good disinfectant and is used to purify water and as a bleach, improves the atmosphere in closed systems, disinfects objects and food, and accelerates the ripening of grains and fruits. In a chemical laboratory, an ozonizer is often used to produce ozone, which is necessary for some methods of chemical analysis and synthesis. Rubber is easily destroyed even under the influence of low concentrations of ozone. In some industrial cities, a significant concentration of ozone in the air leads to the rapid deterioration of rubber products if they are not protected by antioxidants. Ozone is very toxic. Continuous inhalation of air, even with very low concentrations of ozone, causes headaches, nausea and other unpleasant conditions.

One of the most important elements on our planet is oxygen. The chemical properties of this substance allow it to participate in biological processes, and increased activity makes oxygen an important participant in all known chemical reactions. In a free state, this substance is present in the atmosphere. In a bound state, oxygen is a part of minerals, rocks, complex substances that make up various living organisms. The total amount of oxygen on Earth is estimated at 47% of the total mass of our planet.

Oxygen designation

In the periodic system, oxygen occupies the eighth cell of this table. Its international name is oxigenium. In chemical records it is denoted by the Latin letter "O". Atomic oxygen does not occur in the natural environment, its particles combine to form paired gas molecules, the molecular mass of which is 32 g / mol.

Air and oxygen

Air is a mixture of several common gases on Earth. Most in the air mass of nitrogen - 78.2% by volume and 75.5% by weight. Oxygen takes only the second place in volume - 20.9%, and in mass - 23.2%. Third place is assigned to noble gases. The remaining impurities - carbon dioxide, water vapor, dust, etc. - occupy only a fraction of a percent in the total air mass.

The whole mass of natural oxygen is a mixture of three isotopes - 16 O, 17 O, 18 O. The percentage of these isotopes in the total mass of oxygen is 99.76%, 0.04% and 0.2%, respectively.

Physical and chemical properties of oxygen

One liter of air under normal conditions weighs 1.293 g. When the temperature drops to -140 ° C, the air becomes a colorless transparent liquid. Despite the low boiling point, air can be kept in a liquid state even at room temperature. To do this, the liquid must be placed in the so-called Dewar vessel. Immersion in liquid oxygen fundamentally changes the usual properties of objects.

Ethyl alcohol and many gases become solid objects, mercury acquires hardness and ductility, and a rubber ball loses its elasticity and crumbles at the slightest impact.

Oxygen dissolves in water, albeit in small quantities - seawater contains 3-5% oxygen. But even such a small amount of this gas laid the foundation for the existence of fish, shellfish and various marine organisms that receive oxygen from the water to support their own life-support processes.

The structure of the oxygen atom

The described properties of oxygen are primarily explained by the internal structure of this element.

Oxygen belongs to the main subgroup of the sixth group of elements of the periodic system. There are six electrons in the outer electron cloud of the element, four of which occupy p-orbitals, and the remaining two are located on s-orbitals. Such an internal structure leads to high energy costs aimed at breaking electronic bonds - it is easier for an oxygen atom to borrow two missing electrons to an external orbital than to give its six. Therefore, the covalence of oxygen in most cases is equal to two. Thanks to two free electrons, oxygen easily forms diatomic molecules, which are characterized by high bond strength. Only with an applied energy of more than 498 J / mol do molecules break down and atomic oxygen forms. The chemical properties of this element allow it to react with all known substances, excluding helium, neon and argon. The rate of interaction depends on the reaction temperature and on the nature of the substance.

Chemical properties of oxygen

With various substances, oxygen enters into the formation of oxides, and these reactions are characteristic of both metals and non-metals. Compounds of oxygen with metals are called basic oxides - a classic example is magnesium oxide and calcium oxide. The interaction of metal oxides with water leads to the formation of hydroxides, confirming the active chemical properties of oxygen. With non-metals, this substance forms acid oxides - for example, sulfur trioxide SO 3. The interaction of this element with water produces sulfuric acid.

Chemical activity

With the vast majority of elements, oxygen interacts directly. The exceptions are gold, halogens and platinum. The interaction of oxygen with some substances is significantly accelerated in the presence of catalysts. For example, a mixture of hydrogen and oxygen in the presence of platinum reacts even at room temperature. With a deafening explosion, the mixture turns into ordinary water, an important component of which is oxygen. The chemical properties and high activity of the element explain the release of a large amount of light and heat; therefore, chemical reactions with oxygen are often called combustion.

Combustion in pure oxygen is much more intense than in air, although the amount of heat released during the reaction will be approximately the same, but the process is much faster due to the lack of nitrogen and the combustion temperature becomes higher.

Oxygen production

In 1774, the English scientist D. Priestley isolated an unknown gas from the decomposition of mercury oxide. But the scientist did not associate the released gas with the already known substance that is part of the air. Only a few years later did the great Lavoisier study the physicochemical properties of the oxygen obtained in this reaction, and proved its identity with the gas contained in the air. In today's world, oxygen is obtained from air. In laboratories I use industrial oxygen, which is supplied by cylinders under a pressure of about 15 MPa. Pure oxygen can also be obtained in laboratory conditions, the standard method for its production is the thermal decomposition of potassium permanganate, which proceeds according to the formula:

Ozone production

If electricity is passed through oxygen or air, then a characteristic odor will appear in the atmosphere, portending the appearance of a new substance - ozone. Ozone can also be obtained from chemically pure oxygen. The formation of this substance can be expressed by the formula:

This reaction cannot proceed independently - for its successful completion, external energy is required. But the reverse conversion of ozone to oxygen occurs spontaneously. The chemical properties of oxygen and ozone vary greatly. Ozone differs from oxygen in density, melting point and boiling point. Under normal conditions, this gas is blue in color and has a characteristic odor. Ozone has a greater electrical conductivity and is better soluble in water than oxygen. The chemical properties of ozone are explained by the process of its decay - when a molecule of this substance decomposes, a diatomic oxygen molecule is formed plus one free atom of this element, which reacts aggressively with other substances. For example, the reaction of the interaction of ozone and oxygen is known: 6Ag + O 3 \u003d 3Ag 2 O

But ordinary oxygen does not combine with silver even at high temperatures.

In nature, the active decay of ozone is fraught with the formation of so-called ozone holes, which endanger life processes on our planet.

Oxygen formsperoxides   with an oxidation state of −1.
   - For example, peroxides are obtained 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 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, by cooling the flame of burning hydrogen with ice, along with water, hydrogen peroxide is formed:
   H 2 + O 2 → H 2 O 2

Peroxides   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 O 3 - 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. Receive by reaction:
   PtF 6 + O 2 → O 2 PtF 6

Oxygen fluoride
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 (Dioxide Fluoride), O 2 F 2, unstable, oxidation state +1. Obtained from a mixture of fluorine with oxygen in a glow discharge at a temperature of −196 ° C.

By passing a glow discharge through a mixture of fluorine with oxygen at 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, burning, decay. In its free form, the element exists in two allotropic modifications: O 2 and O 3 (ozone).

Oxygen application

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 for the production of steel involves 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 oxidizers of rocket fuel (the specific impulse of a hydrogen-ozone mixture exceeds the specific impulse for a pair of hydrogen-fluorine and hydrogen-oxygen fluoride).

In medicine

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

In the food industry

In the food industry, oxygen is registered as a food additive. E948like propellant and packing gas.

The biological role of oxygen

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

Toxic Derivatives of Oxygen

Some oxygen derivatives (the so-called reactive oxygen species), such as singlet oxygen, hydrogen peroxide, superoxide, ozone and a 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 radicals can form in the cells and tissues of humans and animals and cause oxidative stress.

Oxygen isotopes

Oxygen has three stable isotopes: 16 O, 17 O and 18 O, the average content of which is 99.759%, 0.037% and 0.204% of the total number of oxygen atoms on Earth, respectively. The sharp predominance of the lightest of the 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. 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 half-life data 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 of development of chemistry. From ancient times it was known that air was needed for combustion, but for many centuries the combustion process remained incomprehensible. Only in the XVII century. Mayov and Boyle independently expressed the idea that some substance was contained in the air that supports combustion, but this completely rational hypothesis was not developed then, since the idea of \u200b\u200bburning as a process of combining a burning body with a certain component of air seemed while contradicting such an obvious act as the fact that during combustion there is a decomposition of the burning body into elementary components. It is on this basis at the turn of the XVII century. the phlogiston theory originated 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 and 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 incentives for the systematic studies of the combustion processes of substances undertaken by Lavoisier. Oxygen was discovered in the early 70s of the XVIII century.

The first message about 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 the candle burned more brightly than in ordinary air, and a smoldering torch burst out. Priestley determined some of the properties of the new gas and called it daphlogisticated air. However, two years earlier in Priestley (1772) Scheele also received oxygen by decomposition of mercury oxide and other methods. Scheele called this gas fire air (Feuerluft). Scheele could make a message about his discovery only in 1777.

In 1775, Lavoisier spoke to the Paris Academy of Sciences with the message that he managed to get "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 empirical (Air empireal, Air vital) basis of vital air (Base de l "air vital). The almost simultaneous discovery of oxygen by several scientists in different countries caused controversy over priority. Priestley was particularly persistent in recognizing himself as a discoverer. Essentially, these disputes have not ended yet. A detailed study of the properties of oxygen and its role in combustion and the formation of oxides led Lavoisier to the incorrect conclusion that this gas is an acid-forming principle. In 1779, in accordance with this conclusion, Lavoisier introduced a new name for oxygen - the acid-forming principle (principe acidifiant ou principe oxygine). The word oxygine Lavoisier appearing in this complex name derived from Greek - acid and "I produce."

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 porbitals. 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 the compounds are always negatively charged (so \u003d 2 or -1). The exception is OF 2 and O 2 F 2 fluorides.

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

General characteristic of the element

Oxygen is the most abundant element on Earth, it accounts 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 1,400 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 the proteins, fats and carbohydrates that make up living organisms. The well-known role of oxygen for respiration, for oxidation processes.

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

Opened by the Swede C. Scheele (1771 - 1772) and the Englishman J. Priestley (1774). The first used heating saltpeter, the second - mercury oxide (+2). The name was given by A. Lavoisier (“oxygenigenium” - “acid-producing”).

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

The structure of the ozone molecule

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

Physical properties of oxygen

O 2 - gas without color, odor and taste, so pl. –218.7 ° C, bp –182.96 ° С, 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 - distillation of liquid air and electrolysis of water:

2Н 2 О → 2Н 2 + О 2

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

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

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

4. The 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

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

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

If K 2 O 2 and K 2 O 4 are mixed in uniformly (i.e. equimolar) amounts, then 1 mol of O 2 will be released per 1 mol of absorbed CO 2.

Chemical properties of oxygen

Oxygen supports combustion. Burning - b the rapid process of oxidation of a substance, accompanied by the release of a large amount of heat and light. To prove that there is oxygen in the flask, and not some other gas, it is necessary to lower the smoldering bore into the flask. In oxygen, a smoldering torch flares up brightly. Combustion of various substances in air is a redox process in which oxygen is an oxidizing agent. Oxidizing agents are substances that “take away” electrons from reducing substances. The good oxidizing properties of oxygen can easily be explained by the structure of its outer electron shell.

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

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

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

The fine powder of iron (the so-called pyrophoric iron) spontaneously ignites in air, forming Fe 2 O 3, and the steel wire burns in oxygen if it is heated beforehand:

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 proceeds at a temperature above 1200 o C or in an electric 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 (oxygen deficiency),

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

Ozone

Ozone is chemically more active 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, in 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 destructive ultraviolet radiation of the sun. A thin ozone layer absorbs this radiation, and it does not reach the Earth's surface. Significant fluctuations in the thickness and extent of this layer over time (the so-called ozone holes) are observed, the causes of such fluctuations have not yet been elucidated.

The use of oxygen O   2: for the intensification of the processes of producing pig iron and steel, in the smelting of non-ferrous metals, as an oxidizing agent in various chemical industries, for life support on submarines, as an oxidizing agent for rocket fuel (liquid oxygen), in medicine, and for welding and cutting of metals.

The use of ozone O 3:   for disinfecting drinking water, wastewater, air, for bleaching fabrics.

Chemistry lesson 8 class

Topic:   Oxygen, its general characteristic. Being in nature. Obtaining oxygen and its physical properties.

The purpose of the lesson:   continue the formation of the concepts “chemical element”, “simple substance”, “chemical reaction”. To form ideas about methods for producing oxygen in the laboratory. Introduce the concept of the catalyst, physical properties, characterize the element according to the table D.I. Mendeleev. Improve your whiteboard skills.

Basic concepts. Catalysts.

Expected Learning Outcomes

Subject.   To be able to distinguish between the concepts of "chemical element", "simple substance" on the example of oxygen. Be able to characterize the physical properties and methods of collecting oxygen.

Meta subject. To develop the ability to work according to plan, formulate, argue, organize educational cooperation and joint activities with the teacher and peers.

Personal.   To form a responsible attitude towards learning, a readiness for self-education.

The main activities of students. Describe the chemical element according to the proposed plan. Describe the chemical reactions observed during the demonstration experiment. Participate in a joint discussion of the results. Draw conclusions from the results of experiments.

Demonstrations. Obtaining oxygen from hydrogen peroxide.

During the classes

Learning new material.

1. Frontal conversation:

What gas supports breathing and burning?

What information about oxygen do you already know from courses in natural sciences, botany?

What substances do oxygen contain? (water, sand, rocks, minerals, proteins, fats, carbohydrates).

General characteristics of the chemical element of oxygen:

Chemical sign (O).

Relative atomic mass (16).

Valency (II).

The chemical formula of a simple substance (O2).

Relative molecular weight of a simple substance (32).

Give a characteristic of element No. 8, based on its position in the periodic table of chemical elements Mendeleev. (serial number - 8, atomic mass - 16, IV - group number, period number - 2).

Being in nature.

Oxygen is the most common chemical element in the earth's crust (49%). Air contains 21% oxygen gas. Oxygen is an important part of organic compounds of great importance to living organisms.

Physical properties: oxygen is a colorless gas, without taste and odor, sparingly soluble in water (in 100 volumes of water - 3.1 volume of oxygen). Oxygen is slightly heavier than air (Mr (O2) \u003d 2x16 \u003d 32, p air \u003d 29).

2. Experiments on the production of oxygen.

Getting in the lab.

For the first time, oxygen gas was obtained in 1774. scientist Joseph Priestley. When calcining mercury (II) oxide, Priestley received “air”:

The scientist decided to investigate the effect of the obtained gas on the candle flame: under the influence of this gas, the candle flame became dazzlingly bright, and the iron wire burned out in the stream of gas obtained. Mice placed in a vessel with this gas breathed easily, the scientist himself tried to inhale this gas and noted that breathing is easy.

In the school laboratory, we get this gas from hydrogen peroxide. To observe the physical properties of oxygen, repeat the rules safety precautions.

We put a little manganese (IV) oxide MnO2 in a test tube with a solution of hydrogen peroxide, a violent reaction begins with the release of oxygen. The evolution of oxygen is confirmed by a smoldering speck (it flashes and burns). At the end of the reaction, manganese (IV) oxide settles to the bottom, it can be used again. Consequently, manganese (IV) oxide accelerates the decomposition of hydrogen peroxide, but is not consumed.

Definition:

Substances that accelerate chemical reactions, but themselves are not consumed and are not part of the reaction products, are called catalysts.

2Н2О2 MnO2 2Н2О + О2

In the school laboratory, oxygen is obtained in another way:

By heating potassium permanganate

2KMnO4 \u003d K2MnO4 + MnO2 + O2

Manganese (IV) oxide accelerates yet another oxygen production reaction - the decomposition reaction when heating potassium chlorate KClO3 (bertholate salt): 2KSlO3 MnO2 2KSl + 3O2

3. Work with the textbook:

On p. 75 read about the use of catalysts in industry.

In fig. 25 and fig. 26 shows methods for collecting oxygen. What physical properties known to you are based on the methods of collecting oxygen by air displacement? (oxygen is heavier than air: 32 29), by water displacement? (oxygen is slightly soluble in water). How to assemble a device for collecting oxygen by air displacement? (Fig. 25) Answer: the tube for collecting oxygen should be located bottom to bottom. How can oxygen be detected or proven in a vessel? (by flashing smoldering smudges).

from. 75 read the textbook article "Receiving in the industry." What physical property of oxygen is such a method for its production based on? (liquid oxygen has a boiling point higher than liquid nitrogen, so nitrogen will evaporate and oxygen will remain).

II.Consolidation of knowledge, skills.

What substances are called catalysts?

from. 76 test items.

Work in pairs. Choose two correct answers:

Chemical element oxygen:

1. colorless gas

2. has a serial number of 8 (+)

3. is part of the air

4. is a part of water (+)

5. A bit heavier than air.

4. The simple substance is oxygen:

1. has an atomic mass of 16

2. included in water

3. supports breathing and burning (+)

4. formed during the decomposition of hydrogen peroxide (+).

5. Fill in the table:

General characteristics of oxygen
Being in nature
Getting a) in the laboratory b) in industry
Physical properties

Calculate the mass fraction of the chemical element of oxygen in the oxide of sulfur (VI). SO3

W \u003d (nxAr): Mr x 100%

W (O) \u003d (3x16): 80x100% \u003d 60%

How to recognize which flask contains carbon dioxide and oxygen? (with the help of a smoldering torch: in oxygen it flashes brightly, in carbon dioxide it goes out).