Hydrogen was discovered in the second half of the 18th century by the English scientist in the field of physics and chemistry G. Cavendish. He managed to isolate the substance in its pure state, began studying it and described its properties.

This is the story of the discovery of hydrogen. During the experiments, the researcher determined that it is a flammable gas, the combustion of which in the air produces water. This led to the definition quality composition water.

What is hydrogen

The French chemist A. Lavoisier first announced hydrogen as a simple substance in 1784, since he determined that its molecule contains atoms of the same type.

The name of the chemical element in Latin sounds like hydrogenium (read “hydrogenium”), which means “water-giving.” The name refers to the combustion reaction that produces water.

Characteristics of hydrogen

Designation of hydrogen N. Mendeleev assigned the first atomic number to this chemical element, placing it in the main subgroup of the first group and the first period and conditionally in the main subgroup of the seventh group.

The atomic weight (atomic mass) of hydrogen is 1.00797. Molecular weight H 2 is equal to 2 a. e. Molar mass numerically equal to it.

It is represented by three isotopes that have a special name: the most common protium (H), heavy deuterium (D), radioactive tritium (T).

It is the first element that can be completely separated into isotopes in a simple way. It is based on high difference isotope masses. The process was first carried out in 1933. This is explained by the fact that only in 1932 an isotope with mass 2 was discovered.

Physical properties

IN normal conditions The simple substance hydrogen in the form of diatomic molecules is a gas, colorless, tasteless and odorless. Slightly soluble in water and other solvents.

Crystallization temperature - 259.2 o C, boiling point - 252.8 o C. The diameter of hydrogen molecules is so small that they have the ability to slowly diffuse through a number of materials (rubber, glass, metals). This property is used when it is necessary to purify hydrogen from gaseous impurities. When n. u. hydrogen has a density of 0.09 kg/m3.

Is it possible to transform hydrogen into a metal by analogy with the elements located in the first group? Scientists have found that hydrogen, under conditions when the pressure approaches 2 million atmospheres, begins to absorb infrared rays, which indicates the polarization of the molecules of the substance. Perhaps, at even higher pressures, hydrogen will become a metal.

This is interesting: there is an assumption that on the giant planets, Jupiter and Saturn, hydrogen is found in the form of a metal. It is assumed that metallic solid hydrogen is also present in the earth's core, due to the ultra-high pressure created by the earth's mantle.

Chemical properties

Both simple and complex substances enter into chemical interaction with hydrogen. But the low activity of hydrogen needs to be increased by creating appropriate conditions - increasing the temperature, using catalysts, etc.

When heated, simple substances such as oxygen (O 2), chlorine (Cl 2), nitrogen (N 2), sulfur (S) react with hydrogen.

If you ignite pure hydrogen at the end of a gas outlet tube in air, it will burn evenly, but barely noticeably. If you place the gas outlet tube into the atmosphere pure oxygen, then combustion will continue with the formation of water droplets on the walls of the vessel, as a result of the reaction:

The combustion of water is accompanied by the release of a large amount of heat. It is an exothermic compound reaction in which hydrogen is oxidized by oxygen to form the oxide H 2 O. It is also a redox reaction in which hydrogen is oxidized and oxygen is reduced.

The reaction with Cl 2 occurs similarly to form hydrogen chloride.

The interaction of nitrogen with hydrogen requires high temperature and high pressure, as well as the presence of a catalyst. The result is ammonia.

As a result of the reaction with sulfur, hydrogen sulfide is formed, the recognition of which is facilitated by the characteristic smell of rotten eggs.

The oxidation state of hydrogen in these reactions is +1, and in the hydrides described below – 1.

When reacting with some metals, hydrides are formed, for example, sodium hydride - NaH. Some of these complex compounds are used as fuel for rockets, as well as in thermonuclear power.

Hydrogen also reacts with substances from the complex category. For example, with copper (II) oxide, formula CuO. To carry out the reaction, copper hydrogen is passed over heated powdered copper (II) oxide. During the interaction, the reagent changes its color and becomes red-brown, and droplets of water settle on the cold walls of the test tube.

Hydrogen is oxidized during the reaction, forming water, and copper is reduced from oxide to a simple substance (Cu).

Applications

Hydrogen has great value for humans and is used in a variety of areas:

1. In chemical production it is raw materials, in other industries it is fuel. Petrochemical and oil refining enterprises cannot do without hydrogen.
2. In the electric power industry, this simple substance acts as a cooling agent.
3. In ferrous and non-ferrous metallurgy, hydrogen plays the role of a reducing agent.
4. This helps create an inert environment when packaging products.
5. Pharmaceutical industry - uses hydrogen as a reagent in the production of hydrogen peroxide.
6. Weather balloons are filled with this light gas.
7. This element is also known as a fuel reducer for rocket engines.

Scientists unanimously predict that hydrogen fuel will take the lead in the energy sector.

Receipt in industry

In industry, hydrogen is produced by electrolysis, which is subjected to chlorides or hydroxides of alkali metals dissolved in water. It is also possible to obtain hydrogen directly from water using this method.

The conversion of coke or methane with water vapor is used for these purposes. Methane decomposition at elevated temperature also produces hydrogen. Liquefaction of coke oven gas by the fractional method is also used for the industrial production of hydrogen.

Obtained in the laboratory

In the laboratory, a Kipp apparatus is used to produce hydrogen.

The reagents are hydrochloric acid or sulfuric acid and zinc. The reaction produces hydrogen.

Finding hydrogen in nature

Hydrogen is more common than any other element in the Universe. The bulk of stars, including the Sun, and other cosmic bodies makes up hydrogen.

IN earth's crust it is only 0.15%. It is present in many minerals, all organic matter oh, and also in the water that covers 3/4 of the surface of our planet.

Traces of pure hydrogen can be found in the upper atmosphere. It is also found in a number of flammable natural gases.

Gaseous hydrogen is the least dense, and liquid hydrogen is the densest substance on our planet. With the help of hydrogen, you can change the timbre of your voice if you inhale it and speak as you exhale.

The most powerful hydrogen bomb is based on the splitting of the lightest atom.

Let's look at what hydrogen is. Chemical properties and the production of this non-metal is studied in the course of inorganic chemistry at school. It is this element that heads Mendeleev’s periodic table, and therefore deserves a detailed description.

Brief information about opening an element

Before looking at the physical and chemical properties of hydrogen, let's find out how this important element was found.

Chemists who worked in the sixteenth and seventeenth centuries repeatedly mentioned in their writings the flammable gas that is released when acids are exposed to active metals. In the second half of the eighteenth century, G. Cavendish managed to collect and analyze this gas, giving it the name “combustible gas.”

The physical and chemical properties of hydrogen were not studied at that time. Only at the end of the eighteenth century A. Lavoisier was able to establish through analysis that this gas could be obtained by analyzing water. A little later he began to call new element hydrogene, which translated means “giving birth to water.” Hydrogen owes its modern Russian name to M. F. Solovyov.

Being in nature

The chemical properties of hydrogen can only be analyzed based on its occurrence in nature. This element is present in the hydro- and lithosphere, and is also part of minerals: natural and associated gas, peat, oil, coal, oil shale. It is difficult to imagine an adult who would not know that hydrogen is a component of water.

In addition, this nonmetal is found in animal organisms in the form nucleic acids, proteins, carbohydrates, fats. On our planet, this element is found in free form quite rarely, perhaps only in natural and volcanic gas.

In the form of plasma, hydrogen makes up approximately half the mass of stars and the Sun, and is also part of the interstellar gas. For example, in free form, as well as in the form of methane and ammonia, this non-metal is present in comets and even some planets.

Physical properties

Before considering the chemical properties of hydrogen, we note that under normal conditions it is gaseous substance lighter than air, having several isotopic forms. It is almost insoluble in water and has high thermal conductivity. Protium, which has a mass number of 1, is considered its lightest form. Tritium, which has radioactive properties, is formed in nature from atmospheric nitrogen when neurons expose it to UV rays.

Features of the structure of the molecule

To consider the chemical properties of hydrogen and the reactions characteristic of it, let us dwell on the features of its structure. This diatomic molecule contains a covalent nonpolar chemical bond. The formation of atomic hydrogen is possible through the interaction of active metals with acid solutions. But in this form, this non-metal can exist only for a short period of time; almost immediately it recombines into a molecular form.

Chemical properties

Let's consider the chemical properties of hydrogen. In most of the compounds that this chemical element forms, it exhibits an oxidation state of +1, which makes it similar to active (alkali) metals. The main chemical properties of hydrogen that characterize it as a metal:

• interaction with oxygen to form water;
• reaction with halogens, accompanied by the formation of hydrogen halide;
• producing hydrogen sulfide by combining with sulfur.

Below is the equation for reactions characterizing the chemical properties of hydrogen. Please note that as a non-metal (with oxidation state -1) it acts only in reaction with active metals, forming corresponding hydrides with them.

Hydrogen at ordinary temperatures reacts inactively with other substances, so most reactions occur only after preheating.

Let's take a closer look at some of the chemical interactions of the element that heads the periodic table chemical elements Mendeleev.

The reaction of water formation is accompanied by the release of 285.937 kJ of energy. At elevated temperatures (more than 550 degrees Celsius), this process is accompanied by a strong explosion.

Among those chemical properties of hydrogen gas that have found significant application in industry, its interaction with metal oxides is of interest. It is through catalytic hydrogenation that in modern industry metal oxides are processed, for example, pure metal is isolated from iron scale (mixed iron oxide). This method allows for efficient recycling of scrap metal.

Ammonia synthesis, which involves the interaction of hydrogen with air nitrogen, is also in demand in modern chemical industry. Among the conditions for this chemical interaction Note the pressure and temperature.

Conclusion

It is hydrogen that is a low-active chemical substance under normal conditions. As the temperature rises, its activity increases significantly. This substance is in demand in organic synthesis. For example, by hydrogenation, ketones can be reduced to secondary alcohols, and aldehydes can be converted into primary alcohols. In addition, by hydrogenation it is possible to convert unsaturated hydrocarbons of the ethylene and acetylene class into saturated compounds of the methane series. Hydrogen is rightly considered simple substance, in demand in modern chemical production.

• Designation - H (Hydrogen);
• Latin name - Hydrogenium;
• Period - I;
• Group - 1 (Ia);
• Atomic mass - 1.00794;
• Atomic number - 1;
• Atomic radius = 53 pm;
• Covalent radius = 32 pm;
• Electron distribution - 1s 1;
• melting temperature = -259.14°C;
• boiling point = -252.87°C;
• Electronegativity (according to Pauling/according to Alpred and Rochow) = 2.02/-;
• Oxidation state: +1; 0; -1;
• Density (no.) = 0.0000899 g/cm 3 ;
• Molar volume = 14.1 cm 3 /mol.

Binary compounds of hydrogen with oxygen:

Hydrogen (“giving birth to water”) was discovered by the English scientist G. Cavendish in 1766. It is the simplest element in nature - a hydrogen atom has a nucleus and one electron, which is probably why hydrogen is the most abundant element in the Universe (accounting for more than half the mass of most stars).

About hydrogen we can say that “the spool is small, but expensive.” Despite its "simplicity", hydrogen provides energy to all living beings on Earth - there is continuous thermonuclear reaction during which one helium atom is formed from four hydrogen atoms, this process is accompanied by the release of a colossal amount of energy (for more details, see Nuclear fusion).

In the earth's crust mass fraction hydrogen is only 0.15%. Meanwhile, the overwhelming number (95%) of all known on Earth chemicals contain one or more hydrogen atoms.

In compounds with non-metals (HCl, H 2 O, CH 4 ...), hydrogen gives up its only electron to more electronegative elements, exhibiting an oxidation state of +1 (more often), forming only covalent bonds(See Covalent bond).

In compounds with metals (NaH, CaH 2 ...), hydrogen, on the contrary, accepts another electron into its only s-orbital, thus trying to complete its electronic layer, exhibiting an oxidation state of -1 (less often), often forming an ionic bond (see Ionic bond), because the difference in electronegativity of the hydrogen atom and the metal atom can be quite large.

H 2

In the gaseous state, hydrogen exists in the form of diatomic molecules, forming a nonpolar covalent bond.

Hydrogen molecules have:

• great mobility;
• great strength;
• low polarizability;
• small size and weight.

Properties of hydrogen gas:

• the lightest gas in nature, colorless and odorless;
• poorly soluble in water and organic solvents;
• dissolves in small quantities in liquid and hard metals(especially in platinum and palladium);
• difficult to liquefy (due to its low polarizability);
• has the highest thermal conductivity of all known gases;
• when heated, it reacts with many non-metals, exhibiting the properties of a reducing agent;
• at room temperature it reacts with fluorine (an explosion occurs): H 2 + F 2 = 2HF;
• reacts with metals to form hydrides, exhibiting oxidizing properties: H 2 + Ca = CaH 2;

In compounds, hydrogen exhibits its reducing properties much more strongly than its oxidizing properties. Hydrogen is the most powerful reducing agent after coal, aluminum and calcium. The reducing properties of hydrogen are widely used in industry to obtain metals and nonmetals (simple substances) from oxides and gallides.

Fe 2 O 3 + 3H 2 = 2Fe + 3H 2 O

Reactions of hydrogen with simple substances

Hydrogen accepts an electron, playing a role reducing agent, in reactions:

• With oxygen(when ignited or in the presence of a catalyst), in a ratio of 2:1 (hydrogen:oxygen) an explosive detonating gas is formed: 2H 2 0 +O 2 = 2H 2 +1 O+572 kJ
• With gray(when heated to 150°C-300°C): H 2 0 +S ↔ H 2 +1 S
• With chlorine(when ignited or irradiated with UV rays): H 2 0 +Cl 2 = 2H +1 Cl
• With fluorine: H 2 0 +F 2 = 2H +1 F
• With nitrogen(when heated in the presence of catalysts or when high blood pressure): 3H 2 0 +N 2 ↔ 2NH 3 +1

Hydrogen donates an electron, playing a role oxidizing agent, in reactions with alkaline And alkaline earth metals with the formation of metal hydrides - salt-like ionic compounds containing hydride ions H - are unstable white crystalline substances.

Ca+H 2 = CaH 2 -1 2Na+H 2 0 = 2NaH -1

It is not typical for hydrogen to exhibit an oxidation state of -1. When reacting with water, the hydrides decompose, reducing water to hydrogen. The reaction of calcium hydride with water is as follows:

CaH 2 -1 +2H 2 +1 0 = 2H 2 0 +Ca(OH) 2

Reactions of hydrogen with complex substances

• at high temperature hydrogen reduces many metal oxides: ZnO+H 2 = Zn+H 2 O
• methyl alcohol is obtained by the reaction of hydrogen with carbon monoxide (II): 2H 2 +CO → CH 3 OH
• In hydrogenation reactions, hydrogen reacts with many organic substances.

More detailed equations chemical reactions hydrogen and its compounds are discussed on the page "Hydrogen and its compounds - equations of chemical reactions involving hydrogen."

Applications of hydrogen

• in nuclear energy, hydrogen isotopes are used - deuterium and tritium;
• in the chemical industry, hydrogen is used for the synthesis of many organic substances, ammonia, hydrogen chloride;
• in the food industry, hydrogen is used in the production of solid fats through the hydrogenation of vegetable oils;
• for welding and cutting metals, the high combustion temperature of hydrogen in oxygen (2600°C) is used;
• in the production of some metals, hydrogen is used as a reducing agent (see above);
• Since hydrogen is a light gas, it is used in aeronautics as a filler balloons, balloons, airships;
• Hydrogen is used as a fuel mixed with CO.

Recently, scientists have been paying a lot of attention to the search for alternative sources of renewable energy. One of the promising areas is “hydrogen” energy, in which hydrogen is used as fuel, the combustion product of which is ordinary water.

Methods for producing hydrogen

Industrial methods for producing hydrogen:

• methane conversion (catalytic reduction of water vapor) with water vapor at high temperature (800°C) on a nickel catalyst: CH 4 + 2H 2 O = 4H 2 + CO 2 ;
• conversion of carbon monoxide with water vapor (t=500°C) on a Fe 2 O 3 catalyst: CO + H 2 O = CO 2 + H 2 ;
• thermal decomposition of methane: CH 4 = C + 2H 2;
• gasification of solid fuels (t=1000°C): C + H 2 O = CO + H 2 ;
• electrolysis of water (a very expensive method that produces very pure hydrogen): 2H 2 O → 2H 2 + O 2.

Laboratory methods for producing hydrogen:

• action on metals (usually zinc) with hydrochloric or dilute sulfuric acid: Zn + 2HCl = ZCl 2 + H 2 ; Zn + H 2 SO 4 = ZnSO 4 + H 2;
• interaction of water vapor with hot iron filings: 4H 2 O + 3Fe = Fe 3 O 4 + 4H 2.

IN periodic table has its own specific location, which reflects the properties it exhibits and speaks about its electronic structure. However, among all of them there is one special atom that occupies two cells at once. It is located in two groups of elements that are completely opposite in their 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, let us consider its characteristics and properties in more detail.

Hydrogen as a chemical element

Hydrogen is a group 1 element 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 atomic number of hydrogen is 1, the number of electrons is the same, and, accordingly, 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 for hydrogen is immediately double.
2. The fact that it contains only one electron on its outer surface allows it to successfully exhibit both oxidizing and reducing properties. In addition, after donating an electron, it remains with a free orbital, which takes part in the formation chemical bonds according to the donor-acceptor mechanism.
3. Hydrogen is a strong reducing agent. Therefore, his main place is considered to be 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 metals, it can also be an oxidizing agent, accepting an electron. These compounds are called hydrides. According to this feature, it heads the subgroup of halogens with which it 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 benchmark for lightness.

Thus, it is obvious that the hydrogen atom is a completely unique element, unlike all other elements. 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 its graphical formula will be written using a single sigma H-H bond. The mechanism of bond formation between atoms is covalent nonpolar.

1. Steam methane reforming.
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 various salts, since the melts do not lead to a 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. Interaction of alkali and alkaline earth metals with water.

To collect the hydrogen produced, you must hold the test tube upside down. After all, this gas cannot be collected in the same way as, for example, carbon dioxide. This is hydrogen, it is much lighter than air. It evaporates quickly, and large quantities Explodes when mixed with air. Therefore, the test tube should be inverted. After filling it, it must be closed with a rubber stopper.

To check the purity of the collected hydrogen, you should bring a lit match to the neck. If the clap is dull and quiet, it means the gas is clean, with minimal air impurities. If it is loud and whistling, it is dirty, with a large proportion of foreign components.

Areas of use

When hydrogen is burned, such a large amount of energy (heat) is released that this gas is considered the most profitable fuel. Moreover, it is environmentally friendly. However, to date its application in this area is limited. This is due to ill-conceived and unsolved problems of synthesizing pure hydrogen, which would be suitable for use as fuel in reactors, engines and portable devices, as well as residential heating boilers.

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

There are several main areas in which the gas we are considering is used.

1. Chemical syntheses. Hydrogenation is used to produce soaps, margarines, and plastics. With the participation of hydrogen, methanol and ammonia, as well as other compounds, are synthesized.
2. In the food industry - as additive E949.
3. Aviation industry (rocket science, aircraft manufacturing).
4. Electric power industry.
5. Meteorology.
6. Environmentally friendly fuel.

Obviously, hydrogen is as important as it is abundant in nature. The various compounds it forms 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. General formula- HHal. Of particular importance among them is hydrogen chloride. It is a gas that dissolves in water to form a solution of hydrochloric acid. This acid is widely used in almost all chemical syntheses. Moreover, both organic and inorganic. Hydrogen chloride is a compound with the empirical formula HCL and is one of the largest produced in our country annually. Hydrogen halides also include hydrogen iodide, hydrogen fluoride and hydrogen bromide. They all form the corresponding acids.
2. Volatile Almost all of them are quite poisonous gases. For example, hydrogen sulfide, methane, silane, phosphine and others. At the same time, they are very flammable.
3. Hydrides are compounds with metals. They belong to the class of salts.
4. Hydroxides: bases, acids and amphoteric compounds. They necessarily contain hydrogen atoms, one or more. Example: NaOH, K 2, H 2 SO 4 and others.
5. Hydrogen hydroxide. 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 H 2 O 2.
7. Numerous organic compounds: hydrocarbons, proteins, fats, lipids, vitamins, hormones, essential oils and others.

It is obvious that the variety of compounds of the element we are considering is very large. This once again confirms its high importance for nature and humans, as well as for all living beings.

- this is the best solvent

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

It is in aquatic environment almost everything happens chemical processes. 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 can exist in three states of aggregation:

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

Depending on the isotope of hydrogen included in the molecule, three types of water are distinguished.

1. Light or protium. An isotope with mass number 1. Formula - H 2 O. This is the usual form that all organisms use.
2. Deuterium or heavy, its formula is D 2 O. Contains the isotope 2 H.
3. Super heavy or tritium. The formula looks like T 3 O, isotope - 3 H.

The reserves of fresh protium water on the planet are very important. There is already a shortage of it in many countries. Methods are being developed for treating salt water to produce drinking water.

Hydrogen peroxide is a universal remedy

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

Other name of this connection- peroxide. It is in this form that 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 disinfecting them. However, it has been proven that this increases the healing time of the wound.

Hydrogen peroxide is also used in rocket fuel, in industry for disinfection and bleaching, and as a foaming agent for the production of appropriate materials (foam, for example). Additionally, peroxide helps clean aquariums, bleach hair, and whiten teeth. However, it causes harm to tissues, so it is not recommended by specialists for these purposes.

In the periodic table, hydrogen is located in two groups of elements that are completely opposite in their properties. This feature makes it completely unique. Hydrogen is not just an element or substance, but is also an integral part of many complex compounds, an organogenic and biogenic element. Therefore, let's look at its properties and characteristics in more detail.

The release of flammable gas during the interaction of metals and acids was observed back in the 16th century, that is, during the formation of chemistry as a science. The famous English scientist Henry Cavendish studied the substance starting in 1766 and gave it the name “combustible air.” When burned, this gas produced water. Unfortunately, the scientist’s adherence to the theory of phlogiston (hypothetical “ultrafine matter”) prevented him from coming to the right conclusions.

The French chemist and naturalist A. Lavoisier, together with the engineer J. Meunier and with the help of special gasometers, synthesized water in 1783, and then analyzed it through the decomposition of water vapor with hot iron. Thus, scientists were able to come to the right conclusions. They found that “combustible air” is not only part of water, but can also be obtained from it.

In 1787, Lavoisier suggested that the gas under study was a simple substance and, accordingly, was one of the primary chemical elements. He called it hydrogene (from Greek words hydor - water + gennao - I give birth), i.e. “giving birth to water.”

The Russian name “hydrogen” was proposed in 1824 by the chemist M. Soloviev. The determination of the composition of water marked the end of the “phlogiston theory.” At the turn of the 18th and 19th centuries, it was established that the hydrogen atom is very light (compared to the atoms of other elements) and its mass was taken as the basic unit for comparing atomic masses, receiving a value equal to 1.

Physical properties

Hydrogen is the lightest of all known to science substances (it is 14.4 times lighter than air), its density is 0.0899 g/l (1 atm, 0 °C). This material melts (solidifies) and boils (liquefies), respectively, at -259.1 ° C and -252.8 ° C (only helium has lower boiling and melting temperatures).

The critical temperature of hydrogen is extremely low (-240 °C). For this reason, its liquefaction is a rather complex and costly process. The critical pressure of the substance is 12.8 kgf/cm², and the critical density is 0.0312 g/cm³. Among all gases, hydrogen has the highest thermal conductivity: at 1 atm and 0 °C it is equal to 0.174 W/(mxK).

The specific heat capacity of the substance under the same conditions is 14.208 kJ/(kgxK) or 3.394 cal/(gh°C). This element is slightly soluble in water (about 0.0182 ml/g at 1 atm and 20 °C), but well soluble in most metals (Ni, Pt, Pa and others), especially in palladium (about 850 volumes per volume of Pd ).

The latter property is associated with its ability to diffuse, and diffusion through a carbon alloy (for example, steel) can be accompanied by the destruction of the alloy due to the interaction of hydrogen with carbon (this process is called decarbonization). IN liquid state the substance is very light (density - 0.0708 g/cm³ at t° = -253 °C) and fluid (viscosity - 13.8 spoise under the same conditions).

In many compounds, this element exhibits a +1 valency (oxidation state), like sodium and other alkali metals. It is usually considered as an analogue of these metals. Accordingly, he heads group I of the periodic system. In metal hydrides, the hydrogen ion exhibits a negative charge (the oxidation state is -1), that is, Na+H- has a structure similar to Na+Cl- chloride. In accordance with this and some other facts (proximity physical properties element “H” and halogens, the ability to replace it with halogens in organic compounds) Hydrogene belongs to group VII of the periodic system.

Under normal conditions, molecular hydrogen has low activity, directly combining only with the most active of non-metals (with fluorine and chlorine, with the latter in the light). In turn, when heated, it interacts with many chemical elements.

Atomic hydrogen has increased chemical activity (compared to molecular hydrogen). With oxygen it forms water according to the formula:

Н₂ + ½О₂ = Н₂О,

releasing 285.937 kJ/mol of heat or 68.3174 kcal/mol (25 °C, 1 atm). Under normal temperature conditions, the reaction proceeds rather slowly, and at t° >= 550 °C it is uncontrollable. The explosive limits of a hydrogen + oxygen mixture by volume are 4–94% H₂, and a hydrogen + air mixture is 4–74% H₂ (a mixture of two volumes of H₂ and one volume of O₂ is called detonating gas).

This element is used to reduce most metals, as it removes oxygen from oxides:

Fe₃O₄ + 4H₂ = 3Fe + 4H₂O,

CuO + H₂ = Cu + H₂O, etc.

Hydrogen forms hydrogen halides with different halogens, for example:

H₂ + Cl₂ = 2HCl.

However, when reacting with fluorine, hydrogen explodes (this also happens in the dark, at -252 ° C), with bromine and chlorine it reacts only when heated or illuminated, and with iodine - only when heated. When interacting with nitrogen, ammonia is formed, but only on a catalyst, at elevated pressures and temperatures:

ЗН₂ + N₂ = 2NN₃.

When heated, hydrogen reacts actively with sulfur:

H₂ + S = H₂S (hydrogen sulfide),

and much more difficult with tellurium or selenium. Hydrogen reacts with pure carbon without a catalyst, but at high temperatures:

2H₂ + C (amorphous) = CH₄ (methane).

This substance reacts directly with some of the metals (alkali, alkaline earth and others), forming hydrides, for example:

H₂ + 2Li = 2LiH.

Important practical significance have interactions between hydrogen and carbon(II) monoxide. In this case, depending on the pressure, temperature and catalyst, different organic compounds are formed: HCHO, CH₃OH, etc. Unsaturated hydrocarbons during the reaction become saturated, for example:

С n Н₂ n + Н₂ = С n Н₂ n ₊₂.

Hydrogen and its compounds play an exceptional role in chemistry. It conditions acid properties so-called protic acids, tends to form with different elements hydrogen bond, which has a significant impact on the properties of many inorganic and organic compounds.

Hydrogen production

The main types of raw materials for the industrial production of this element are oil refining gases, natural combustible and coke oven gases. It is also obtained from water through electrolysis (in places where electricity is available). One of the most important methods production of material from natural gas The catalytic interaction of hydrocarbons, mainly methane, with water vapor (the so-called conversion) is considered. For example:

CH₄ + H₂O = CO + ZN₂.

Incomplete oxidation of hydrocarbons with oxygen:

CH₄ + ½O₂ = CO + 2H₂.

The synthesized carbon monoxide (II) undergoes conversion:

CO + H₂O = CO₂ + H₂.

Hydrogen produced from natural gas is the cheapest.

For the electrolysis of water, direct current is used, which is passed through a solution of NaOH or KOH (acids are not used to avoid corrosion of the equipment). In laboratory conditions, the material is obtained by electrolysis of water or as a result of a reaction between hydrochloric acid and zinc. However, ready-made factory material in cylinders is more often used.

This element is isolated from oil refining gases and coke oven gas by removing all other components of the gas mixture, since they liquefy more easily during deep cooling.

This material began to be produced industrially back in late XVIII century. Back then it was used to fill balloons. At the moment, hydrogen is widely used in industry, mainly in the chemical industry, for the production of ammonia.

Mass consumers of the substance are producers of methyl and other alcohols, synthetic gasoline and many other products. They are obtained by synthesis from carbon monoxide (II) and hydrogen. Hydrogene is used for the hydrogenation of heavy and solid liquid fuels, fats, etc., for the synthesis of HCl, hydrotreating of petroleum products, as well as in metal cutting/welding. The most important elements For nuclear energy are its isotopes - tritium and deuterium.

Biological role of hydrogen

About 10% of the mass of living organisms (on average) comes from this element. It is part of water and the most important groups of natural compounds, including proteins, nucleic acids, lipids, and carbohydrates. What is it used for?

This material plays a decisive role: in maintaining the spatial structure of proteins (quaternary), in implementing the principle of complementarity of nucleic acids (i.e., in the implementation and storage of genetic information), and in general in “recognition” at the molecular level.

The hydrogen ion H+ takes part in important dynamic reactions/processes in the body. Including: in biological oxidation, which provides living cells with energy, in biosynthesis reactions, in photosynthesis in plants, in bacterial photosynthesis and nitrogen fixation, in maintaining acid-base balance and homeostasis, in membrane transport processes. Along with carbon and oxygen, it forms the functional and structural basis of life phenomena.