Hydrogen - what kind of substance? Chemical and physical properties of hydrogen

Each chemical element in the periodic system has its own specific position, which reflects its properties and speaks of its electronic structure. However, there is among all one special atom, which occupies just two cells. It is located in two completely opposite groups of elements according to the properties exhibited. It's hydrogen. Such features make it unique.

Hydrogen is not just an element, it is 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 table.

1. The ordinal number of hydrogen is 1, the number of electrons is the same, correspondingly, the same number of protons. The atomic mass is 1.00795. There are three isotopes of a given element with mass numbers 1, 2, 3. However, the properties of each of them are very different, since the increase in mass even by unity is just double for hydrogen.
2. The fact that it contains only one electron at the external energy level allows it to successfully manifest to it both oxidative and reducing properties. In addition, after the electron is released, a free orbital remains in it, which takes part in the formation of chemical bonds by the donor-acceptor mechanism.
3. Hydrogen is a strong reducing agent. Therefore, the main group is the first group of the main subgroup, where he heads the most active metals - alkaline.
4. However, when interacting with strong reducing agents, such as, for example, metals, it can be an oxidizer by taking an electron. These compounds are called hydrides. On this basis, he leads a subgroup of halogens, with which it is similar.
5. Due to the very small atomic mass, hydrogen is considered to be the lightest element. In addition, its density is also very small, so it is also a standard of lightness.

Thus, it is obvious that the hydrogen atom is a completely unique element, unlike any other element. Consequently, its properties are also special, and the simple and complex substances formed 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 H ₂ , and graphical - through a single sigma-bond H-H. The mechanism of formation of the bond between atoms is covalent nonpolar.

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

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

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

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 activity.

Physical properties

Physical parameters of hydrogen has the following:

1. The boiling point is (-252.76 ⁰ C).
2. The melting point is (-259.2 ^° C).
3. In the indicated temperature range is a colorless liquid that does not have an odor.
4. At very high pressure there are snow-like crystals of solid hydrogen.
5. Under certain conditions (high pressure and low temperatures) it is possible to change to a metallic state.
6. Virtually nerastvorim in water, so it is possible to collect by the method of displacement of water in the production in the laboratory.
7. Under normal conditions, hydrogen is a gas that does not smell, color, and taste.
8. It is a combustible and explosive substance.
9. It dissolves well 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, the bonds are weak, so they are easily destroyed.

Chemical properties

As already mentioned above, hydrogen is able to exhibit both reducing and oxidizing properties. Possible oxidation states of the element +1; -1. Therefore, it is often used in the 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 low-active metals under the influence of high temperatures or strong illumination (photochemical initiation of reactions) also form hydrides.

Reductive properties of hydrogen

1. Interaction under normal conditions only with fluorine (as a strong oxidant). As a result, hydrogen fluoride or hydrofluoric acid HF is formed.
2. Interaction with virtually all non-metals, but under certain rather harsh 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 of producing metals, called hydrogenothermia.

Separately, we should single out the reactions that are used in organic synthesis. They are called hydrogenation-saturation with hydrogen and dehydrogenation, that is, by its cleavage from the molecule. Based on these transformation methods, a variety of hydrocarbons and other organic compounds are produced.

Being in nature

Hydrogen is the most common substance on our planet and beyond. After all, almost all interstellar space and stars consist precisely of 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 propagation specifically in the earth's crust, then hydrogen ranks second in the number of atoms after oxygen, its approximately 17%. In the free form is rare, only in minor amounts in the composition of dry air. The most common connection of this element is water. It is in its composition that he meets on the planet.

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

Receiving

There are different ways of obtaining the gas we are considering. These include several industrial and laboratory synthesis options.

Industrial methods of hydrogen production :

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

Laboratory methods of hydrogen production:

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

To collect the resulting hydrogen, it is necessary to hold the tube upside down. After all, this gas can not be collected as, for example, carbon dioxide. It's hydrogen, it's much lighter than air. Rapidly volatilizes, and in large quantities when mixed with air explodes. Therefore, the test tube should be turned over. After filling it, it must be closed with a rubber stopper.

To check the purity of the collected hydrogen, you should bring a lighted match to the neck. If the cotton is deaf and quiet - it means the gas is clean, with minimal air impurities. If loud and whistling - dirty, with a large percentage of foreign components.

Areas of use

When the hydrogen is burned, so much energy (heat) is released, that this gas is considered the most profitable fuel. In addition, it is environmentally friendly. However, to date, its use in this area is limited. This is due to the unreasonable and unresolved 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 for residential buildings.

After all, the methods of obtaining this gas are quite expensive, therefore, it is necessary to develop a special synthesis method first. Such that will allow to receive a product in a large volume and with minimal expenses.

It is possible to distinguish several main areas in which the gas considered by us finds application.

1. Chemical synthesis. Based on hydrogenation, soaps, margarines, and plastics are obtained. With the participation of hydrogen, methanol and ammonia are synthesized, as well as other compounds.
2. In the food industry - as an additive E949.
3. The aviation industry (rocket engineering, aircraft construction).
4. Power engineering.
5. Meteorology.
6. Fuel of an ecologically pure kind.

It is obvious that hydrogen is as important as it is in nature. An even greater role is played by the various compounds formed by it.

Hydrogen compounds

These are complex substances containing hydrogen atoms. Several basic types of such substances can be distinguished.

1. Hydrogen halides. The general formula is HHal. Hydrogen chloride is of particular importance among them. It is a gas that dissolves in water to form a solution of hydrochloric acid. This acid is widely used in virtually all chemical syntheses. And both organic and inorganic. Hydrogen chloride is a compound that has the empirical formula of HCL and is one of the largest in terms of production in our country annually. Hydrogen, hydrogen fluoride and hydrogen bromide are also hydrogen halides. They all form the corresponding acids.
2. Volatile hydrogen compounds of nonmetals. Virtually all of them are sufficiently poisonous gases. For example, hydrogen sulphide, methane, silane, phosphine and others. At the same time very flammable.
3. Hydrides - compounds with metals. Relate to the class of salts.
4. Hydroxides: bases, acids and amphoteric compounds. Their composition necessarily includes hydrogen atoms, one or more. Example: NaOH, K ₂ [AL (OH) ₄ ], H ₂ SO ₄ and others.
5. Hydrogen hydroxide. This compound is more commonly known as water. Another name is hydrogen oxide. The empirical formula looks like this: H ₂ O.
6. Hydrogen peroxide. This is the strongest oxidizer, the formula of which has 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 significance for nature and man, as well as for all living beings.

Hydrogen oxide is the best solvent

As mentioned above, the common name of this substance is water. It consists of two hydrogen atoms and one oxygen, connected together by covalent polar bonds. The water molecule is a dipole, which explains many of the properties it exhibits. In particular, it is a universal solvent.

It is in the water environment that virtually all chemical processes occur. Internal reactions of plastic and energy metabolism in living organisms are also carried out with the help of hydrogen oxide.

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

• liquid;
• Gas (steam);
• Solid (ice).

Depending on the hydrogen isotope, which is part of the molecule, there are three types of water.

1. Light or protict. Isotope with a mass number of 1. Formula - H ₂ O. This is a familiar form that all organisms use.
2. Deuterium or heavy, its formula is D ₂ O. It contains the isotope ² H.
3. Super-heavy or tritium. The formula looks like T ₃ O, isotope - ³ N.

Very important are the reserves of fresh protie water on the planet. Already in many countries there is a lack of it. Methods are being developed for treating salt water for drinking purposes.

Hydrogen peroxide is a universal remedy

This compound, as mentioned above, is an excellent oxidizer. However, with strong representatives can behave as a reductant, too. In addition, it has a pronounced bactericidal effect.

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

Also, hydrogen peroxide is used in rocket fuel, in the industry for disinfection and bleaching, as a blowing agent for the production of suitable materials (foam, for example). In addition, peroxide helps to clean aquariums, discolor hair and whiten teeth. However, at the same time it damages the tissues, so specialists are not recommended for this purpose.