Hydrogen - what is this substance? Chemical and physical properties of hydrogen

Each chemical element in the periodic system has its own specific position, which reflects the properties it exhibits and speaks of its electronic structure. However, among all there is one special atom, which occupies two cells at once. It is located in two completely opposite groups of elements in terms of their manifested properties. This is hydrogen. Such features make it unique.

Hydrogen is not just an element, but also a simple substance, as well as an integral part of many complex compounds, a biogenic and organogenic element. Therefore, we consider its characteristics and properties in more detail.

Hydrogen as a chemical element

Hydrogen is an element of the first group of the main subgroup, as well as the seventh group of the main subgroup in the first small period. This period consists of only two atoms: helium and the element we are considering. Let us describe the main features of the position of hydrogen in the periodic system.

1. The sequence number of hydrogen is 1, the number of electrons is the same, respectively, the number of protons is the same. Atomic mass - 1,00795. There are three isotopes of this element with mass numbers 1, 2, 3. However, the properties of each of them are very different, since an increase in mass even by one is exactly double for hydrogen.
2. The fact that it contains only one electron at the external energy level allows one to successfully exhibit both oxidizing and reducing properties. In addition, after the recoil of the electron, he remains with a free orbital, which takes part in the formation of chemical bonds by the donor-acceptor mechanism.
3. Hydrogen is a powerful reducing agent. Therefore, his main place is considered the first group of the main subgroup, where he leads the most active metals - alkaline.
4. However, when interacting with strong reducing agents, such as, for example, metals, it can also be an oxidizing agent, taking an electron. These compounds are called hydrides. On this basis, he leads a subgroup of halogens with which he is similar.
5. Due to its very small atomic mass, hydrogen is considered the lightest element. In addition, its density is also very low, so it is also a standard of lightness.

Thus, it is obvious that the hydrogen atom is completely unique, unlike all other elements. Therefore, its properties are also special, and the formed simple and complex substances are very important. Let's consider them further.

Simple substance

If we talk about this element as a molecule, then we must say that it is diatomic. That is, hydrogen (a simple substance) is a gas. Its empirical formula will be written as ₂ , and its graphic formula will be written through a single sigma-connection -. The mechanism of bonding between atoms is covalent non-polar.

Even Henry Cavendish in 1766 managed to discover this substance. It was he who proved that hydrogen is a gas, and one that can explode in air. Later properties were well studied, it became clear that this substance is the lightest among the known.

Later, Lavoisier gave the name (both to the element and to the substance based on it) in Latin - hydrogenium, which means "giving birth to water". In 1781, the pioneer of this element, Henry Cavendish, proved that water is a combination of hydrogen and oxygen, that is, it is a product of their interaction. And the fact that light gas is also very combustible was known back in the 16th century, this was reflected in the records of Paracelsus.

Thus, molecular hydrogen is a very common in nature and naturally formed gaseous compound, consisting of two atoms, which can explode in air. In addition, a molecule can decay into atoms that take part in nuclear reactions, turning into helium nuclei. These processes continuously occur on the Sun and in space, which are the main suppliers of this compound.

Hydrogen is a substance that can manifest itself both as an oxidizing agent and as a reducing agent. It also finds a very wide application in human activities.

Physical properties

The physical parameters of hydrogen are as follows:

1. Boiling point - (-252.76 ⁰ ).
2. Melting point - (-259.2 ⁰ C).
3. In the indicated temperature range, it is a colorless, odorless liquid.
4. At very high pressures, snowy crystals of solid hydrogen exist.
5. Under certain conditions (high pressure and low temperatures) it is able to transform into a metallic state.
6. It is practically insoluble in water; therefore, collection by the method of water displacement upon receipt under laboratory conditions is possible.
7. Under normal conditions, hydrogen is a gas that does not have a smell, color or taste.
8. It is flammable and explosive.
9. It is well soluble in metals, as it is able to diffuse through their thickness.
10. Approximately 14.5 times this gas is lighter than air.

The crystal lattice of a simple substance is molecular, bonds are weak, therefore, they are easily destroyed.

Chemical properties

As mentioned above, hydrogen is able to exhibit both reducing and oxidizing properties. Possible oxidation states of element +1; -1. Therefore, it is often used in industry for syntheses and various reactions.

Oxidizing properties of hydrogen

1. Interaction with active metals (alkaline and alkaline earth) under normal conditions leads to the formation of salt-like compounds called hydrides. For example: LiH, CaH ₂ , KH, MgH ₂ and others.
2. Compounds with inactive metals under the influence of high temperatures or strong light (photochemical initiation of reactions) also form hydrides.

The reducing properties of hydrogen

1. Interaction under ordinary conditions only with fluorine (as a strong oxidizing agent). As a result, hydrogen fluoride or hydrofluoric acid HF is formed.
2. Interaction with almost all non-metals, but under certain rather stringent conditions. Examples of compounds: H ₂ S, NH ₃ , H ₂ O, PH ₃ , SiH ₄ and others.
3. Restores metals from their oxides to simple substances. This is one of the industrial methods for producing metals, called hydrogen thermal.

Separately, it is necessary to highlight the reactions that are used in organic syntheses. They are called hydrogenation — hydrogen saturation and dehydrogenation, that is, its cleavage from the molecule. Based on these conversion methods, many hydrocarbons and other organic compounds are obtained.

Being in nature

Hydrogen is the most abundant substance on our planet and beyond. After all, almost all interstellar space and stars consist of just this connection. In space, it can exist in the form:

• plasma
• gas;
• ions;
• atoms;
• molecules.

There are several types of clouds of different density, consisting precisely of this substance.

If we talk about the distribution specifically in the earth's crust, then hydrogen is in second place in the number of atoms after oxygen, its approximately 17%. In its free form is rare, only in small quantities in the composition of dry air. The most common compound of this element is water. It is in its composition that it is found on the planet.

Also, hydrogen is an essential component of any living organism. Moreover, in the human body, this atom accounts for 63%. Hydrogen is an organogenic element; therefore, it forms molecules of proteins, fats, carbohydrates and nucleic acids, as well as many other vital compounds.

Getting

There are different ways to obtain the gas under consideration. These include several industrial and laboratory synthesis options.

Industrial methods for producing hydrogen :

1. Steam methane conversion.
2. Coal gasification - the process involves heating coal to 1000 ⁰ C, resulting in the formation of hydrogen and high-carbon coal.
3. Electrolysis. This method can only be used for aqueous solutions of various salts, since melts do not lead to discharge of water at the cathode.

Laboratory methods for producing hydrogen:

1. Hydrolysis of metal hydrides.
2. The effect of dilute acids on active metals and medium activity.
3. The interaction of alkali and alkaline earth metals with water.

To collect the generated hydrogen, it is necessary to keep the tube upside down. After all, this gas cannot be collected as, for example, carbon dioxide. This is hydrogen, it is much lighter than air. Quickly disappears, and in large quantities when mixed with air explodes. Therefore, the tube should be turned over. After filling it, you need to close it with a rubber stopper.

To check the purity of the collected hydrogen, you should bring a lit match to the neck. If the cotton is deaf and quiet, then the gas is clean, with minimal air admixtures. If it is loud and whistling - dirty, with a large proportion of extraneous components.

Areas of use

When hydrogen is burned, so much energy (heat) is released that this gas is considered the most profitable fuel. In addition, environmentally friendly. However, to date, its use in this area is limited. This is due to ill-conceived and unsolved problems of the synthesis of pure hydrogen, which would be suitable for use as fuel in reactors, engines and portable devices, as well as heating boilers in residential buildings.

After all, the methods for producing this gas are quite expensive, therefore, it is first necessary to develop a special synthesis method. One that will allow you to receive the product in a large volume and at minimal cost.

There are several main areas in which the gas under consideration is used.

1. Chemical syntheses. Soaps, margarines, and plastics are obtained on the basis of hydrogenation. With the participation of hydrogen, methanol and ammonia, as well as other compounds, are synthesized.
2. In the food industry - as an additive E949.
3. Aviation industry (rocket science, aircraft industry).
4. Power industry.
5. Meteorology.
6. Ecologically clean fuel.

Obviously, hydrogen is just as important as it is common in nature. The various compounds formed by him play an even greater role.

Hydrogen compounds

These are complex substances containing hydrogen atoms. There are several main types of such substances.

1. Hydrogen halides. The general formula is HHal. Of particular importance among them is hydrogen chloride. This is a gas that dissolves in water to form a hydrochloric acid solution. This acid is widely used in almost all chemical syntheses. Moreover, both organic and inorganic. Hydrogen chloride is a compound that has the empirical formula HCL and is one of the largest in terms of production in our country annually. Hydrogen halides also include hydrogen iodide, hydrogen fluoride and hydrogen bromide. All of them form the corresponding acids.
2. Volatile hydrogen compounds of non-metals. Almost all of them are quite toxic gases. For example, hydrogen sulfide, methane, silane, phosphine and others. It’s very flammable.
3. Hydrides are compounds with metals. Belong to the class of salts.
4. Hydroxides: bases, acids and amphoteric compounds. They necessarily include hydrogen atoms, one or more. Example: NaOH, K ₂ [AL (OH) ₄ ], H ₂ SO ₄ and others.
5. Hydroxide of hydrogen. This compound is better known as water. Another name is hydrogen oxide. The empirical formula looks like this - H ₂ O.
6. Hydrogen peroxide. This is a strong oxidizing agent, the formula of which is of the form H ₂ O ₂ .
7. Numerous organic compounds: hydrocarbons, proteins, fats, lipids, vitamins, hormones, essential oils and others.

Obviously, the variety of compounds of the element under consideration is very large. This once again confirms its high value for nature and man, as well as for all living beings.

Hydrogen oxide is the best solvent

As mentioned above, the common name for this substance is water. It consists of two hydrogen atoms and one oxygen, interconnected by covalent polar bonds. The water molecule is a dipole; this explains many of its properties. In particular, the fact that it is a universal solvent.

It is in the aquatic environment that almost all chemical processes occur. Internal reactions of plastic and energy metabolism in living organisms are also carried out using hydrogen oxide.

Water is rightfully considered the most important substance on the planet. It is known that no living organism can live without it. On Earth, it is able to exist in three aggregate states:

• liquid;
• gas (steam);
• solid (ice).

Three types of water are distinguished depending on the isotope of hydrogen that is part of the molecule.

1. Light or prickly. An isotope with a mass number of 1. The formula is H ₂ O. This is the familiar form that all organisms use.
2. Deuterium or heavy, its formula is D ₂ O. Contains an isotope of ² N.
3. Extra heavy or tritium. The formula looks like T ₃ O, the isotope - ³ N.

The reserves of fresh protium water on the planet are very important. Already now in many countries its lack is felt. Methods are being developed for treating salt water in order to obtain potable water.

Hydrogen peroxide is a universal remedy.

This compound, as mentioned above, is an excellent oxidizing agent. However, with strong representatives, it can also act as a reducing agent. In addition, it has a pronounced bactericidal effect.

Another name for this compound is peroxide. It is in this form that it is used in medicine. The 3% solution of crystalline hydrate of the compound in question is a medical medicine that is used to treat small wounds in order to disinfect them. However, it is proved that the healing of the wound increases with time.

Hydrogen peroxide is also used in rocket fuel, in industry for disinfection and bleaching, as a foaming agent for the production of appropriate materials (polystyrene, for example). In addition, peroxide helps cleanse aquariums, bleach hair, and whiten teeth. However, it harms tissues, therefore, it is not recommended by specialists for these purposes.