Among all the substances on Earth, a special place is occupied by what life provides - oxygen gas. It is his presence that makes our planet unique among all others, special. Thanks to this substance, so many wonderful creatures live in the world: plants, animals, people. Oxygen is a completely indispensable, unique and extremely important compound. Therefore, we will try to find out what it represents, what characteristics it has.
Chemical element oxygen: characteristic
First, we characterize the location of this element in the periodic system. This can be done in a few points.
- The serial number is 8.
- Atomic mass - 15,99903.
- It is located in the sixth group of the main subgroup of the second period of the system.
- The nuclear charge is +8, the number of protons - 8, electrons - 8, neutrons - 8. Thus, a double magic number is obtained, due to which the stability of the main isotopic form is 16 O.
- The Latin name of the element is oxygen. Russian is oxygen, this name is derived from the phrase "giving birth to acid." There is also a synonym, sometimes it is called oxygen.
The analysis of the electronic structure of the atom deserves special attention, since it is precisely with it that the stability of the molecule and the manifest physical and chemical properties are explained.
Molecule structure
The electronic configuration of the atom is represented by the formula 1s 2 2s 2 2p 4 . From this record it is obvious that until the completion of the energy level and the creation of the coveted octet, oxygen lacks two electrons. This explains its following characteristics:
- diatomic oxygen molecule;
- the oxidation state of an element is always -2 (except for peroxides and fluorine oxide, in which it changes by -1 and +2, respectively);
- is the strongest oxidizing agent;
- easily reacts even under ordinary conditions;
- capable of forming explosive compounds.
Now consider the issue of structure. How is an oxygen molecule formed? Firstly, the mechanism of formation of covalent non-polar, that is, due to the socialization of electrons of each atom. Thus, the bond is also covalent non-polar. Moreover, it is double, since each of the atoms has two unpaired electrons at the external level. You can very simply depict what oxygen looks like. The formula is: O 2 or O = O.
Due to the presence of such a bond, the molecule is very stable. For many reactions with her participation, special conditions are required: high pressure, heating, use of catalysts.
As a chemical element, oxygen is an atom having three isotopes stably existing in nature. Their mass numbers are respectively 16, 17, 18. However, the percentage ratio is very different, since 16 About 99.759%, and the rest is less than 0.5%. Therefore, the most common and stable isotope is precisely with a mass number of 16.
Simple substance oxygen
If we talk about this element as a simple connection, then we should immediately indicate the state of aggregation under ordinary conditions. Oxygen is a gas that has no taste, no color, no smell. A diatomic molecule, which is the most abundant substance on the planet, after hydrogen and a noble gas of helium.
There are other aggregative states of this substance. So, at a negative temperature of -183 0 C, oxygen condenses into a beautiful blue liquid. If you exceed the threshold of -200 0 C, then the liquid will grow into bright blue monoclinic needle-shaped crystals.
In total, three main types of the existence of oxygen in the solid state are distinguished.
- Alpha form (Ξ±-O 2 ). It exists at temperatures below 200 0 C.
- Beta form (Ξ²-O 2 ). The temperature range is -200-400 0 .
- Gamma form (Ξ³-O 2 ). The interval is from -400 to -500 0 C.
Oxygen is one of the most important and significant gases. Not only for the life of living beings on the planet, but also for nature as a whole. It is difficult to name a natural mineral or compound, in the composition of which it would not be included as an element.
Discovery story
The first mention of the fact that the composition of the air contains some kind of gas that supports combustion processes appeared in the VIII century. However, then to study it, to prove its existence and discover it was not a technical possibility. Only after almost a millennium, in the XVIII century, this was done thanks to the work of several scientists.
- 1771 Karl Scheele experimentally established the composition of the air and found out that the main two gases are oxygen and nitrogen.
- Pierre Bayenne conducts experiments on the decomposition of mercury and its oxide and officially records the results.
- 1773 Scheele officially discovers the oxygen element, but does not receive it in its pure form.
- The year 1774, Priestley, irrespective of Scheele, makes the same discovery as he does, and receives pure oxygen by the decomposition of mercury oxide.
- 1775 Antoine Lavoisier gives the name to this element and creates a theory of combustion that has existed for more than one hundred years.
- 1898 Thompson makes society think that air oxygen may end due to large emissions of carbon dioxide into the atmosphere.
- In the same year, Timiryazev proved the opposite, as he explains that the planetβs green plants are the oxygen supplier.
Thus, it became known what oxygen is, what an important and significant gas it is for life. After that, all the physical and chemical properties of the substance were studied, methods for its preparation were examined, and the approximate content in water, the earth's crust, atmosphere and other places of the planet was calculated.
Physical properties
Here are the main physical parameters that can be used to characterize the compound in question.
- Oxygen is a gas under normal conditions, which is an integral part of air (21%). It has no color, taste or smell. Lighter than air, poorly soluble in water.
- It is actively absorbed by coal and metal powders, soluble in organic substances.
- The boiling point is -183 0 .
- Melting point -218.35 0 .
- The density is 0.0014 g / cm 3 .
- The crystal lattice is molecular.
Oxygen has paramagnetic properties in the liquid state.
Chemical properties
Chemistry tells in detail how active the gas in question is, how it behaves in reactions with other substances. Oxygen is able to exhibit several degrees of oxidation, although the most common is -2, which is considered constant. In addition to it, there are compounds in which the values ββare as follows:
The chemical activity is explained by a high electron affinity, since the value of electronegativity according to Polling is 3.44. Only fluorine is higher (4). Therefore, oxygen is a very strong oxidizing agent. At the same time, in reactions with even stronger oxidizing agents, it behaves as a reducing agent, exhibiting a positive oxidation state. For example, in fluorine oxide O +2 F 2 - .
There are a huge number of compounds that include oxygen. These are such classes of substances as:
- oxides;
- peroxides;
- ozonides;
- peroxides;
- acids;
- grounds;
- salts;
- organic molecules.
With all elements, oxygen is able to react under ordinary conditions, except for noble metals, helium, neon and argon and halogens. It does not interact with inert gases under any conditions.
Receiving in the industry
The oxygen content in air and water is so high (21 and 88%, respectively) that the main industrial method for its synthesis is fractional distillation of liquid air and electrolysis of water.
The first method is especially often used. Indeed, a lot of this gas can be released from the air. However, it will not be completely clean. If a higher quality product is needed, then electrolysis processes are launched. The raw material for this is either water or alkali. Sodium or potassium hydroxide is used in order to increase the strength of the conductivity of the solution. In general, the essence of the process is reduced to the decomposition of water.
Getting in the lab
Among laboratory methods, the heat treatment method has become widespread:
- peroxides;
- salts of oxygenated acids.
At high temperatures, they decompose with the release of gaseous oxygen. The process is most often catalyzed by manganese (IV) oxide. They collect oxygen by displacing water, and they find it by a smoldering hole. As you know, in an atmosphere of oxygen, a flame flares up very brightly.
Another substance used to produce oxygen in school chemistry classes is hydrogen peroxide. Even a 3% solution under the action of a catalyst decomposes instantly with the release of pure gas. It only needs to be collected. The catalyst is the same - manganese oxide MnO 2 .
Among the salts most commonly used are:
- bertoletova salt, or potassium chlorate;
- potassium permanganate, or potassium permanganate.
To describe the process, we can give an equation. Oxygen is allocated enough for laboratory and research purposes:
2KClO 3 = 2KCl + 3O 2 β.
Allotropic modifications of oxygen
There is one allotropic modification that oxygen has. The formula of this compound is O 3 , it is called ozone. This is a gas that is formed under natural conditions when exposed to ultraviolet lightning and lightning discharges on atmospheric oxygen. Unlike O 2 itself , ozone has a pleasant smell of freshness, which is felt in the air after rain with lightning and thunder.
The difference between oxygen and ozone lies not only in the number of atoms in the molecule, but also in the structure of the crystal lattice. Chemically, ozone is an even stronger oxidizing agent.
Oxygen is a component of air
The distribution of oxygen in nature is very wide. Oxygen is found in:
- rocks and minerals;
- salty and fresh water;
- soil;
- plant and animal organisms;
- air, including the upper atmosphere.
Obviously, all the shells of the Earth are occupied with it - the lithosphere, hydrosphere, atmosphere and biosphere. Especially important is its content in the air. Indeed, it is this factor that allows life forms to exist on our planet, including man.
The composition of the air we breathe is extremely heterogeneous. It includes both constant components and variables. The unchanging and always present are:
- carbon dioxide;
- oxygen;
- nitrogen;
- noble gases.
Variables include water vapor, dust particles, extraneous gases (exhaust, combustion products, rotting, etc.), plant pollen, bacteria, fungi, and others.
The value of oxygen in nature
It is very important how much oxygen is in nature. After all, it is known that on some satellites of large planets (Jupiter, Saturn) were found trace amounts of this gas, but there is no obvious life there. Our Earth has a sufficient amount of it, which in combination with water makes it possible for all living organisms to exist.
In addition to being an active participant in breathing, oxygen also carries out countless oxidation reactions, which release energy for life.
The main suppliers of this unique gas in nature are green plants and some types of bacteria. Thanks to them, a constant balance of oxygen and carbon dioxide is maintained. In addition, ozone builds a protective shield over the entire Earth, which does not allow a large amount of destructive ultraviolet radiation to penetrate.
Only some types of anaerobic organisms (bacteria, fungi) are able to live outside the atmosphere of oxygen. However, there are far fewer of them than those who really need it.
Industrial use of oxygen and ozone
The main areas of use of allotropic modifications of oxygen in industry are as follows.
- Metallurgy (for welding and cutting metals).
- The medicine.
- Agriculture.
- As rocket fuel.
- The synthesis of many chemical compounds, including explosives.
- Purification and disinfection of water.
It is difficult to name at least one process in which this great gas does not take part, a unique substance - oxygen.