What is the positive chemical effect of oxygen on nature. Oxygen Application Report
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 1400 minerals: silica, silicates and aluminosilicates, marbles, basalts, hematite and other minerals and rocks. Oxygen makes up 50-85% of the tissue mass 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.
It was discovered 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. By 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 + 3O 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 oxygen is 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 oxygen valence shell 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. Consequently, 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 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
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 a 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. 
Lecture “Oxygen - a chemical element and a simple substance »
Lecture Plan:
1. Oxygen - a chemical element:
c) The prevalence of a chemical element in nature
2. Oxygen is a simple substance
a) Oxygen production
b) Chemical properties of oxygen
c) The oxygen cycle in nature
d) The use of oxygen
"Dum spiro spero
"(While breathing, I hope ...), - says Latin
Breathing is a synonym for life, and the source of life on Earth is oxygen.
Emphasizing the importance of oxygen for earth processes, Jacob Berzelius said: “Oxygen is the substance around which earth chemistry revolves”The material in this lecture summarizes the previously gained knowledge on the subject of “Oxygen”.
1. Oxygen - a chemical element
a) Characterization of a chemical element - oxygen according to its position in PSChE
Oxygen - an element of the main subgroup of the sixth group, the second period of the periodic system of chemical elements D. I. Mendeleev, with atomic number 8. Denotes by the symbol O (lat.Oxygenium) The relative atomic mass of the chemical element of oxygen is 16, i.e.Ar (O) \u003d 16.
b) Valence possibilities of the oxygen atom
In compounds, oxygen is usually divalent (in oxides), valencyVI does not exist. In its free form it occurs in the form of two simple substances: O 2 (“ordinary” oxygen) and O 3 (ozone). O 2 - a gas without color and odor, with a relative molecular weight \u003d 32. O 3 - gas without color with a pungent odor, with a relative molecular weight \u003d 48.
Attention! H 2 O 2 ( hydrogen peroxide) -O (valency II)
CO (carbon monoxide) - O (valencyIII)
c) The prevalence of the chemical element of oxygen in nature
Oxygen is the most abundant element on Earth, its share (in the composition of various compounds, mainly silicates), accounts for about 49% of the mass of the solid earth's crust. Sea and fresh waters contain a huge amount of bound oxygen - 85.5% (by mass), in the atmosphere the content of free oxygen is 21% by volume and 23% by mass. More than 1,500 compounds of the earth's crust contain oxygen.
Oxygen is a part of many organic substances and is present in all living cells. By the number of atoms in living cells, it is about 20%, by mass fraction - about 65%.
2. Oxygen is a simple substance
a) Oxygen production
Getting in the lab
1) Decomposition of potassium permanganate (potassium permanganate):
2KMnO 4 t˚C \u003d K 2 MnO 4 + MnO 2 + O 2
2) Decomposition of hydrogen peroxide:
2H 2 O 2 MnO2 \u003d 2H 2 O + O 2
3) Decomposition of bertoletova salt:
2KClO 3 t˚C, MnO2 \u003d 2KCl + 3O 2
Receiving in the industry
1) Electrolysis of water
2 H 2 O email. current \u003d 2 H 2 + O 2
2) From the air
AIR pressure, -183˚ C \u003d O 2 (blue liquid)
Currently, in industry, oxygen is obtained from air. In laboratories, small amounts of oxygen can be obtained by heating potassium permanganate (potassium permanganate) KMnO 4 . Oxygen is slightly soluble in water and heavier than air, so it can be obtained in two ways:
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oxygen OXYGEN (lat. Oxygenium), O (read "o"), chemical element with atomic number 8, atomic mass 15,9994. In the periodic system of Mendeleev’s elements, oxygen is located in the second period in the VIA group. Natural oxygen consists of a mixture of three stable nuclides with mass numbers of 16 (it dominates the mixture; it is 99.759% by mass in it), 17 (0.037%) and 18 (0.204%). In its free form, oxygen is a gas without color, odor and taste. Structural Features of O2 Molecule: Atmospheric oxygen consists of diatomic molecules. The dissociation energy of the O2 molecule into atoms is quite high and amounts to 493.57 kJ / mol.
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Chemical properties of oxygen: Oxygen is the second most electronegative element after fluorine; therefore, it exhibits strong oxidizing properties. With most metals, it reacts even at room temperature, forming basic oxides. With non-metals (with the exception of helium, neon, argon), oxygen reacts, as a rule, when heated. So, it reacts with phosphorus at a temperature of ~ 60 ° С, forming Р2О5, with sulfur - at a temperature of about 250 ° С: S + О2 \u003d SO2. Oxygen reacts with graphite at 700 ° С С + О2 \u003d СО2. The interaction of oxygen with nitrogen begins only at 1200 ° С or in an electric discharge N2 + О2 2NО - Q. Oxygen also reacts with many complex compounds, for example, nitric oxide (II) at room temperature: 2NО + О2 \u003d 2NО2.
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Hydrogen sulfide, reacting with oxygen when heated, gives sulfur 2Н2S + О2 \u003d 2S + 2Н2О or sulfur oxide (IV) 2Н2S + ЗО2 \u003d 2SО2 + 2Н2О depending on the ratio between oxygen and hydrogen sulfide. In the above reactions, oxygen is an oxidizing agent. In most oxidation reactions involving oxygen, heat and light are released - such processes are called combustion. Oxygen O3 is an even stronger oxidizing agent than oxygen O2. It is formed in the atmosphere during lightning discharges, due to the specific smell of freshness after a thunderstorm. Typically, ozone is obtained by passing a discharge through oxygen (the reaction is endothermic and highly reversible; the ozone yield is about 5%): ZO2<=>2O3 - 284 kJ. During the interaction of ozone with a solution of potassium iodide, iodine is released, while this reaction does not occur with oxygen: 2KI + O3 + H2O \u003d I2 + 2KOH + O2. The reaction is often used as a quality reaction for the detection of I- or ozone ions. To do this, starch is added to the solution, which gives a characteristic blue complex with released iodine. The reaction is also high-quality because ozone does not oxidize Cl- and Br- ions.
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Oxygen production in industry oxygen is obtained: by fractional distillation of liquid air (nitrogen having a lower boiling point evaporates, but liquid oxygen remains); electrolysis of water. Annually, over 80 million tons of oxygen are received worldwide. In laboratory conditions, oxygen is obtained by the decomposition of a number of salts, oxides, and peroxides: 2KMnO4 -\u003e K2MnO4 + MnO2 + O2, 4K2Cr2O7 -\u003e 4K2CrO4 + 2Cr2O3 + 3O2, 2KNO3 -\u003e 2KNO2 + O2, 2Pb3Og + 2Pb3O4 - 2Pb + 2b + 2b + 2b + 2b + 2b + 2b + 2b + 2b + 2b + 2b + 2b + 2b + 2b + 2b + 2b + 2b + 2b + 2b + 2b + 2b + 2b + 2b + 2g O2, 2BaO -\u003e 2BaO + O2, 2H2O2 -\u003e 2H2O + O2. Oxygen is especially easily liberated as a result of the last reaction, since in hydrogen peroxide H2O2 is not a double, but a single bond between oxygen atoms -O-O-.
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Application The main quantities of oxygen obtained from air are used in metallurgy. Oxygen (rather than air) blasting in blast furnaces can significantly increase the speed of the blast furnace process, save coke and produce better quality cast iron. Oxygen blasting is used in oxygen converters for the conversion of cast iron to steel. Pure oxygen or oxygen-enriched air is used in the production of many other metals (copper, nickel, lead, etc.). Oxygen is used in cutting and welding metals. be under pressure up to 15 MPa. Oxygen cylinders are blue. Liquid oxygen is a powerful oxidizing agent, it is used as a component of rocket fuel. Impregnated with liquid oxygen, such easily oxidized materials as sawdust, cotton wool, coal powder, etc. (these mixtures are called hydroxyquitites) are used as explosives, used, for example, when laying roads in mountains.
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In every plant or animal, there is much more oxygen than any other element (on average about 70%). Human muscle tissue contains 16% oxygen, bone tissue - 28.5%; In total, the average person's body (body weight 70 kg) contains 43 kg of oxygen. In animals and humans, oxygen enters mainly through the respiratory system (free oxygen) and through water (bound oxygen). The body’s need for oxygen is determined by the level (intensity) of metabolism, which depends on the mass and surface of the body, age, gender, nutrition, external conditions, etc. In ecology, the ratio of total respiration (i.e., total oxidative processes) of a community is determined organisms to its total biomass. Small amounts of oxygen are used in medicine: oxygen (from the so-called oxygen pillows) is given for some time to breathe for patients who have difficulty breathing. It must be borne in mind, however, that prolonged inhalation of oxygen-enriched air is harmful to human health. High oxygen concentrations cause the formation of free radicals in the tissues, which disrupt the structure and function of biopolymers. Similar effects on the body have ionizing radiation. Therefore, a decrease in the oxygen content (hypoxia) in tissues and cells when the body is irradiated with ionizing radiation has a protective effect - the so-called oxygen effect.
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Distribution and forms of oxygen in nature Oxygen is the most common element of the earth’s crust, hydrosphere, and living organisms. Its clark in the lithosphere is 47%, even higher is the clark in the hydrosphere - 82% and living matter - 70%. Over 1,400 oxygen-containing minerals are known in which dozens of elements of the periodic system are its companions. Oxygen is a cyclical element of the classification of V.I. Vernadsky, he participates in numerous cycles of various scales - from small, within a specific landscape, to the grandiose connecting the biosphere with the foci of magmatism. Oxygen accounts for approximately half of the total mass of the earth's crust, 89% of the mass of the oceans. In the atmosphere, oxygen is 23% of the mass and 21% of the volume
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On the earth's surface, green plants decompose water during photosynthesis and release free oxygen (O2) into the atmosphere. As Vernadsky noted, free oxygen is the most powerful figure among all the known chemical bodies of the earth's crust. Therefore, in most systems of the biosphere, for example, in soils, ground, river, and sea waters, oxygen acts as a real geochemical dictator, determines the geochemical identity of the system, and the development of oxidative reactions in it. Over billions of years of geological history, plants have made our planet’s atmosphere oxygen, the air we breathe made life The number of oxidation reactions that consume free oxygen is huge. In the biosphere, they are mainly of a biochemical nature, i.e., carried out by bacteria, although purely chemical oxidation is known. In soils, silts, rivers, seas and oceans, groundwater horizons - wherever there are organic substances and water, the activity of microorganisms that oxidize organic compounds develops.
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In most natural waters containing free oxygen - a strong oxidizing agent, there are organic compounds - strong reducing agents. Therefore, all geochemical systems with free oxygen are nonequilibrium and rich in free energy. The disequilibrium is expressed more sharply, the more in the system of living matter. Everywhere in the biosphere, where water that does not contain free oxygen (with a reducing environment) meets this gas, an oxygen geochemical barrier arises, on which Fe, Mn, S and other elements are concentrated with the formation of ores of these elements. Previously, there was a prevailing misconception that, as the depth in the earth's crust deepens, the environment becomes more restorative, but this does not fully correspond to reality. On the earth's surface, in the landscape, both sharply oxidizing and sharply reducing conditions can be observed. Redox zoning is observed in lakes - photosynthesis develops in the upper zone and oxygen saturation and oversaturation are observed. But in the deep parts of the lake, in the silts, only the decomposition of organic substances occurs. Below the biosphere, in the zone of metamorphism, the degree of recovery of the medium often decreases, as in magma foci. The most reducing conditions in the biosphere arise in areas of vigorous decomposition of organic substances, and not at maximum depths. Such areas are characteristic of both the earth's surface and aquifers.
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The oxygen cycle Oxygen is the most common element on Earth. Seawater contains 85.82% oxygen, 23.15% by weight or 20.93% by volume in atmospheric air, and 47.2% by weight in the earth's crust. This concentration of oxygen in the atmosphere is kept constant due to the process of photosynthesis. In this process, green plants convert carbon dioxide and water into carbohydrates and oxygen under the influence of sunlight. The main mass of oxygen is in a bound state; the amount of molecular oxygen in the atmosphere is estimated at 1.5 * 1015 m, which is only 0.01% of the total oxygen content in the earth's crust. In nature, oxygen is of utmost importance. Oxygen and its compounds are indispensable for maintaining life.
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They play a crucial role in the processes of metabolism and respiration. Oxygen is a part of proteins, fats, carbohydrates, of which organisms are “built”; in the human body, for example, contains about 65% oxygen. Most organisms receive the energy necessary to fulfill their vital functions through the oxidation of certain substances with the help of oxygen. The loss of oxygen in the atmosphere as a result of the processes of respiration, decay and burning is compensated by the oxygen released during photosynthesis. Deforestation, soil erosion, various mine workings on the surface reduce the total mass of photosynthesis and reduce the cycle in large areas. Along with this, the photochemical decomposition of water vapor in the upper atmosphere under the influence of ultraviolet rays of the sun appears to be a powerful source of oxygen. Thus, the cycle of oxygen is continuously carried out in nature, maintaining a constant composition of atmospheric air. In addition to the oxygen cycle described above in an unbound form, this element also performs the most important cycle, entering into the composition of water. The water cycle (H2O) consists in the evaporation of water from the surface of land and sea, its transport by air masses and winds, condensation of vapors and the subsequent precipitation in the form of rain, snow, hail, fog.
“Oxygen compounds” - Oxygen compounds N (all nitrogen oxides are endothermic !!!). Oxygen compounds N + 5. Halides N. Binding of Diazot N2. Oxygen compounds N + 3. Thermolysis of ammonium salts. Decomposition of nitrates at T. Oxygen compounds N + 2. Opening items. Nitrides. Properties Oxygen compounds N + 4. Similarly for Li2NH (imide), Li3N (nitride).
"The use of oxygen" - The use of oxygen. The patient is in a special apparatus in an oxygen atmosphere at reduced pressure. The doctor talks with the patient on the phone. Fireman with self-contained breathing apparatus. Outside the earth's atmosphere, man is forced to take with him a supply of oxygen. The main consumers of oxygen are energy, metallurgy and the chemical industry.
Oxygen Chemistry - 1.4 g / l, slightly heavier than air. Combustion reaction. The melting temperature. Oxygen in nature. Boiling temperature. Physical state, color, smell. Physical properties of oxygen. Density. Solubility. Oxygen. Oxidation reactions in which heat and light are released are called combustion reactions.
“Air test” - The number of climatic zones. Answer the questions in writing. Wind changing direction twice a year. Air. The unit of pressure. A mixture of different liquids. Instrument for measuring atmospheric pressure. Combustion-free gas. Air density. To generalize and consolidate knowledge.
"Air chemistry" - Ozone holes. The effects of air pollution. Automobile exhausts, industrial emissions. The greenhouse effect. Identify the main ways to solve the problem of air pollution. Variable air components. The main ways to solve the problem of air pollution. Ecological condition in the districts of Moscow.
"Oxygen. Ozone. Air ”- Perform a test. Complete the task. M.V. Lomonosov. Allotropy. Oxygen. Solve the problem. The composition of the air. Examine the composition of the air. Biological role. Ozone and oxygen. Getting oxygen. The properties of oxygen. A. Lavoisier. Generalization. The use of oxygen. The evolution of oxygen. Check your answers. Laboratory experience.
There are 17 presentations in total
Plan:
Discovery story
Origin of name
Being in nature
Getting
Physical properties
Chemical properties
Application
The biological role of oxygen
Toxic Derivatives of Oxygen
10. Isotopes
Oxygen
Oxygen - an element of the 16th group (according to an outdated classification - the main subgroup of the VI group), the second period of the periodic system of chemical elements D. I. Mendeleev, with atomic number 8. It is designated by the symbol O (lat. Oxygenium). Oxygen - a chemically active non-metal, is the easiest element from the group of chalcogenes. Simple substance oxygen (CAS number: 7782-44-7) under normal conditions, it is a gas without color, taste, and odor, the molecule of which consists of two oxygen atoms (O 2 formula), which is why it is also called oxygen. Liquid oxygen has a light blue color, and solid is a light blue crystals.
There are other allotropic forms of oxygen, for example, ozone (CAS number: 10028-15-6) - under normal conditions, a blue gas with a specific odor, the molecule of which consists of three oxygen atoms (O 3 formula).
Discovery story
It is officially believed that oxygen was discovered by the English chemist Joseph Priestley on August 1, 1774 by decomposing mercury oxide in a hermetically sealed vessel (Priestley sent sunlight to this compound using a powerful lens).
However, Priestley did not initially understand that he had discovered a new simple substance; he believed that he had isolated one of the constituent parts of air (and called this gas “de-logged air”). Priestley announced his discovery to the prominent French chemist Antoine Lavoisier. In 1775, A. Lavoisier established that oxygen is an integral part of air, acids and is found in many substances.
A few years earlier (in 1771) oxygen was received by the Swedish chemist Karl Scheele. He calcined nitrate with sulfuric acid and then decomposed the resulting nitric oxide. Scheele called this gas “fiery air” and described his discovery in a book published in 1777 (precisely because the book was published later than it announced its discovery by Priestley, the latter is considered the discoverer of oxygen). Scheele also reported on his experience with Lavoisier.
An important step that facilitated the discovery of oxygen was the work of the French chemist Pierre Bain, who published work on the oxidation of mercury and the subsequent decomposition of its oxide.
Finally, A. Lavoisier finally understood the nature of the gas obtained, using information from Priestley and Scheele. His work was of great importance, because thanks to it the phlogiston theory, which was dominant at that time and hindered the development of chemistry, was overthrown. Lavoisier conducted an experiment on the combustion of various substances and refuted the theory of phlogiston, publishing the results on the weight of the burned elements. The weight of the ash exceeded the initial weight of the element, which gave Lavoisier the right to assert that during combustion there is a chemical reaction (oxidation) of the substance, in connection with this the mass of the initial substance increases, which refutes the theory of phlogiston.
Thus, the merit of the discovery of oxygen is actually shared between Priestley, Scheele and Lavoisier.
origin of name
The word oxygen (called at the beginning of the 19th century also “acid-base”), its appearance in the Russian language owes to some extent to M. V. Lomonosov, who introduced, along with other neologisms, the word “acid”; Thus, the word “oxygen”, in turn, was a tracing-paper of the term “oxygen” (French oxygène), proposed by A. Lavoisier (from the Greek Greek ὀξύς - “sour” and γεννάω - “give birth”), which translates as "Generating acid", which is associated with its original meaning - "acid", previously implying substances called oxides according to the modern international nomenclature.
Being in nature
Oxygen is the most abundant element on Earth, its share (in the composition of various compounds, mainly silicates) accounts for about 47.4% of the mass of the solid earth's crust. Sea and fresh waters contain a huge amount of bound oxygen - 88.8% (by weight), in the atmosphere the content of free oxygen is 20.95% by volume and 23.12% by weight. More than 1,500 compounds of the earth's crust contain oxygen.
Oxygen is a part of many organic substances and is present in all living cells. By the number of atoms in living cells, it is about 25%, by mass fraction - about 65%.
