Hydrogen appeared. What is hydrogen? Properties and meaning

Liquid hydrogen is one of the aggregate states of hydrogen. Allocate more gaseous and solid state of this element. And if the gaseous form is well known to many, then the other two extreme states raise questions.

History

Liquid hydrogen was obtained only in the thirties of the last century, but before that chemistry had come a long way in mastering this method of gas storage and application.

Artificial cooling began to be used experimentally in the middle of the eighteenth century in England. In 1984 we received liquefied sulfur dioxide and ammonia. Based on these studies, the first refrigerator was developed twenty years later, and thirty years later, Perkins filed an official patent for his invention. In 1851 on the other side Atlantic Ocean John Gorey claimed the rights to create the air conditioner.

It came to hydrogen only in 1885, when the Pole Wroblewski announced in his article the fact that this element is equal to 23 Kelvin, the peak temperature is 33 Kelvin, or 13 atmospheres. After this statement, James Dewar tried to create liquid hydrogen at the end of the 19th century, but he did not succeed in creating a stable substance.

Physical properties

This is characterized by a very low density of matter - hundredths of grams per cubic centimeter. This makes it possible to use relatively small containers to store liquid hydrogen. The boiling point is only 20 Kelvin (-252 Celsius), and this substance freezes already at 14 Kelvin.

The liquid is odorless, colorless and tasteless. Mixing it with oxygen can lead to an explosion half the time. When the boiling point is reached, hydrogen passes into a gaseous state, and its volume increases 850 times.

After liquefaction, hydrogen is placed in insulated containers, which are kept at low pressure and temperatures between 15 and 19 Kelvin.

Hydrogen prevalence

Liquid hydrogen is produced artificially and does not occur in the natural environment. If you do not take into account aggregate states, then hydrogen is the most abundant element not only on planet Earth, but also in the Universe. Stars (including our Sun) are made of it, they fill the space between them. Hydrogen takes part in thermonuclear fusion reactions and can also form clouds.

In the earth's crust, this element takes up only about one percent of the total amount of matter. Its role in our ecosystem can be assessed by the fact that the number of hydrogen atoms is second only to oxygen in quantity. On our planet, almost all reserves of H 2 are in a bound state. Hydrogen is an integral part of all living things.

Usage

Liquid hydrogen (temperature -252 degrees Celsius) is used in the form of a form for storing gasoline and other derivatives of oil refining. Besides, in this moment transport concepts are being created that could use liquefied hydrogen as fuel instead of natural gas. This would reduce the cost of extracting valuable minerals and reduce air emissions. But so far, the optimal engine design has not been found.

Liquid hydrogen is actively used by physicists as a coolant in their experiments with neutrons. Since the mass of an elementary particle and a hydrogen nucleus are practically equal, the exchange of energy between them is very effective.

Benefits and obstacles

Liquid hydrogen makes it possible to slow down the heating of the atmosphere and reduce the amount of greenhouse gases when used as a fuel for cars. When it interacts with air (after passing through an internal combustion engine), water and a small amount of nitrogen oxide will be formed.

However, this idea also has its own difficulties, for example, the way of storing and transporting gas, as well as an increased risk of ignition or even explosion. Even if all precautions are taken, hydrogen evaporation cannot be prevented.

Rocket fuel

Liquid hydrogen (storage temperature up to 20 Kelvin) is one of the components It has several functions:

1. Cooling of engine elements and protection of the nozzle from overheating.
2. Providing traction after mixing with oxygen and heating.

Modern ones work on a combination of hydrogen-oxygen. This helps to achieve the correct speed to overcome the gravity of the earth while maintaining all parts of the aircraft without exposing them to excessive temperatures.

There is currently only one rocket that uses hydrogen entirely as fuel. In most cases, liquid hydrogen is needed to separate the upper stages of rockets or in those devices that will do most of the work in a vacuum. There have been suggestions from researchers to use the half-frozen form of this element to increase its density.

Hydrogens have their own names: H - protium (H), H - deuterium (D) and H - tritium (radioactive) (T).

Simple substance hydrogen - H 2 - light colorless gas. It is flammable and explosive when mixed with air or oxygen. Non-toxic. Let's dissolve in ethanol and a number of metals: iron, nickel, palladium, platinum.

History

Even the medieval scientist Paracelsus noticed that when acids act on iron, bubbles of some kind of "air" are released. But what it was, he could not explain. Now we know that it was hydrogen. “Hydrogen is an example of a gas,” wrote DI Mendeleev, “which at first glance does not differ from air ... Paracelsus, who discovered that the action of certain metals on sulfuric acid produces an airy substance, did not determine its difference from air. Indeed, hydrogen is colorless and odorless, just like air; but, upon closer acquaintance with its properties, this gas turns out to be completely different from air. "

The English chemists of the 18th century, Henry Cavendish and Joseph Priestley, who rediscovered hydrogen, were the first to study its properties. They found it to be an unusually light gas - 14 times lighter than air. If you inflate a rubber ball with it, it will fly up. This property of hydrogen was previously used to fill balloons and airships. True, the first balloon, built by the Montgolfier brothers, was filled not with hydrogen, but with smoke from burning wool and straw. This strange way of getting hot air is due to the fact that the brothers, apparently, were not familiar with the laws of physics; they naively believed that this mixture forms "electric smoke" capable of lifting their light ball. The physicist Charles, who knew Archimedes' law, decided to fill the sphere with hydrogen; Unlike hot air balloons, the French called balloons filled with hydrogen charlier. The first such balloon (it did not carry any load) rose from the Champ de Mars in Paris on August 27, 1783 and flew 20 km in 45 minutes.

In December 1783, Charles, accompanied by the physicist François Robert, in the presence of 400 thousand spectators, took the first flight in a balloon filled with hydrogen. Gay Lussac (also with the physicist Jean Baptiste Biot) set an altitude record in 1804, climbing 7000 meters.

But hydrogen is flammable. Moreover, its mixtures with air explode, and the mixture of hydrogen and oxygen is even called "explosive gas". In May 1937, a fire in a few minutes destroyed the giant German airship "Hindenburg" - it contained 190,000 cubic meters of hydrogen. Then 35 people died. After many accidents, hydrogen is no longer used in aeronautics; it is replaced with helium or hot air.

When hydrogen burns, water is formed - a combination of hydrogen and oxygen. This was proved at the end of 18 by the French chemist Lavoisier. Hence the name of the gas - "giving birth to water". Lavoisier also managed to get hydrogen from water. He passed water vapor through a red-hot iron tube filled with iron filings. Oxygen from water was firmly combined with iron, and hydrogen was liberated in a free form. Now hydrogen is also obtained from water, but in a different way - by means of electrolysis (see. ELECTROLYTIC DISSOCIATION. ELECTROLYTES)

Hydrogen properties

Hydrogen is the most abundant chemical element in the universe. It makes up about half the mass of the Sun and most stars, and is the main element in interstellar space and in gaseous nebulae. Hydrogen is also widespread on Earth. Here it is in a bound state - in the form of connections. So, water contains 11% hydrogen by weight, clay - 1.5%. In the form of compounds with carbon, hydrogen is a part of oil, natural gases, and all living organisms. There is a little free hydrogen in the air, but there is very little of it - only 0.00005%. It enters the atmosphere from volcanoes.

Hydrogen owns many other "records".
Liquid hydrogen- the lightest liquid (density 0.067 g / cm 3 at a temperature of –250 ° C),
Solid hydrogen- the easiest solid(density 0.076 g / cm 3).
Hydrogen atoms Are the smallest of all atoms. However, when the energy of electromagnetic radiation is absorbed, the outer electron of the atom can move farther and farther away from the nucleus. Therefore, an excited hydrogen atom can theoretically be of any size. And practically? In the book World Records in Chemistry, it is said that hydrogen atoms with a diameter of 0.4 mm were allegedly found in interstellar clouds from their spectra (they were recorded by a spectral transition from the 253rd to the 252nd orbital). Atoms of this size can be easily seen with the naked eye! At the same time, a reference is made to an article published in 1991 in the world's most famous journal devoted to chemical education - the Journal of Chemical Education (published in the USA). However, the author of the article was mistaken - he overestimated all dimensions by exactly 100 times (this was reported by the same magazine a year later). This means that the discovered hydrogen atoms have a diameter of “only” 0.004 mm, and such atoms, even if they were “solid”, cannot be seen with the naked eye - only through a microscope. Of course, by atomic standards, 0.004 mm is a huge value, tens of thousands of times larger than the diameter of an unexcited hydrogen atom.

Hydrogen molecules are also very small. Therefore, this gas easily passes through the thinnest slits. A rubber balloon inflated with hydrogen “loses weight” much faster than a balloon inflated with air: hydrogen molecules gradually seep through the smallest pores in the rubber.

If you breathe in hydrogen and start talking, then the frequency of the sounds made will be three times higher than usual. This is enough for the sound of even a low male voice to be unnaturally high, reminiscent of Pinocchio's voice. This happens because the pitch of a whistle, pipe organ or vocal apparatus of a person depends not only on their size and wall material, but also on the gas with which they are filled. The higher the speed of sound in the gas, the higher its tone. The speed of sound depends on the mass of the gas molecules. Hydrogen molecules are much lighter than the nitrogen and oxygen molecules that make up air, and sound propagates in hydrogen almost four times faster than in air. However, inhaling hydrogen is risky: in the lungs, it will inevitably mix with the rest of the air and form an explosive mixture. And if, when you exhale, there is a fire nearby ... This is what happened to the French chemist, director of the Paris Science Museum, Pilatre de Rozier (1756–1785). Somehow he decided to check what would happen if hydrogen was inhaled; before him, no one had conducted such an experiment. Not noticing any effect, the scientist decided to make sure that hydrogen penetrated into the lungs. He inhaled the gas well once more, and then exhaled it into the candle fire, expecting to see a flash of flame. However, the hydrogen in the lungs of the courageous experimenter was mixed with air and a violent explosion occurred. "I thought that all my teeth were flying out along with the roots," he wrote later, very pleased with the experience, which almost cost him his life.

The history of obtaining deuterium and tritium

Deuterium

In addition to "ordinary" hydrogen (protium, from the Greek protos- the first), its heavy isotope is also present in nature - deuterium(from the Latin deuteros - the second) and in trace amounts superheavy hydrogen - tritium. Long and dramatic searches for these isotopes at first did not give results due to insufficient sensitivity of the instruments. At the end of 1931, a group of American physicists - G. Yuri with his students, F. Brikvedde and J. Murphy, took 4 liters of liquid hydrogen and subjected it to fractional distillation, receiving only 1 ml of the remainder, i.e. reducing the volume by 4 thousand times. It was this last milliliter of liquid after evaporation that was investigated spectroscopically. Experienced spectroscopist Yuri noticed new very weak lines on the spectrogram of enriched hydrogen, which are absent in ordinary hydrogen. In this case, the position of the lines in the spectrum exactly corresponded to his quantum-mechanical calculation of the nuclide 2H (see CHEMICAL ELEMENTS).

After spectroscopic detection of deuterium, it was proposed to separate hydrogen isotopes by electrolysis. Experiments have shown that during the electrolysis of water, light hydrogen is actually released faster than heavy hydrogen. It was this discovery that became the key to the production of heavy hydrogen. The article, which reported on the discovery of deuterium, was published in the spring of 1932, and already in July the results on electrolytic isotope separation were published. In 1934, Harold Clayton Urey received the Nobel Prize in Chemistry for the discovery of heavy hydrogen.

Tritium

On March 17, 1934, in the journal Nature published in England, a small note was published, signed by ML Oliphant, P. Hartek and Rutherford (the name of Lord Rutherford did not require initials when publishing!). Despite the modest title of the note: The effect of transmutation obtained with heavy hydrogen, she informed the world about an outstanding result - the artificial production of the third isotope of hydrogen - tritium. In 1946, a well-known authority on nuclear physics, Nobel laureate W. F. Libby, suggested that tritium is continuously formed as a result of nuclear reactions... However, in nature, tritium is so small (1 atom 1H for 1018 atoms of 3H) that it was possible to detect it only by its weak radioactivity (half-life 12.3 years).

Hydrides

Hydrogen forms compounds - hydrides with many elements. Depending on the second element, hydrides differ greatly in their properties. The most electropositive elements (alkali and heavy alkaline earth metals) form the so-called salt-like ionic hydrides. They are obtained as a result of the direct reaction of a metal with hydrogen under pressure and at elevated temperatures (300–700 ° C) when the metal is in a molten state. Their crystal lattice contains metal cations and H– hydride anions and is constructed similarly to the NaCl lattice. When heated to the melting temperature, salt-like hydrides begin to conduct an electric current, while, in contrast to the electrolysis of aqueous solutions of salts, hydrogen is released not at the cathode, but at the positively charged anode. Salt-like hydrides react with water with the evolution of hydrogen and the formation of an alkali solution, are easily oxidized by oxygen and are used as strong reducing agents.

A number of elements form covalent hydrides, among which the most well-known are the hydrides of Group IV-VI elements, for example, methane CH 4, ammonia NH 3, hydrogen sulfide H 2 S, etc. Covalent hydrides are highly reactive and are reducing agents. Some of these hydrides are unstable and decompose when heated or hydrolyzed with water. An example is SiH 4, GeH 4, SnH 4. From the point of view of structure, boron hydrides are interesting, for example, B 2 H 6, B 6 H 10, B 10 H 14, etc., in which a pair of electrons binds not two, as usual, but three B – H – B atoms. Some mixed hydrides are also referred to as covalent, for example, lithium aluminum hydride LiAlH 4, which has found wide application in organic chemistry as a reducing agent. Hydrides of germanium, silicon, arsenic are used to obtain high-purity semiconductor materials.

Transition metal hydrides are very diverse in properties and structure. Often these are compounds of non-stoichiometric composition, for example, metal-like TiH 1.7, LaH 2.87, etc. When such hydrides are formed, hydrogen is first adsorbed on the metal surface, then it dissociates into atoms that diffuse deep into the crystal lattice of the metal, forming interstitial compounds. Of greatest interest are hydrides of intermetallic compounds, for example, containing titanium, nickel, and rare earth elements. The number of hydrogen atoms per unit volume of such a hydride can be five times greater than even in pure liquid hydrogen! Already at room temperature, the alloys of these metals are capable of rapidly absorbing significant amounts of hydrogen, and when heated, they release it. Thus, reversible "chemical accumulators" of hydrogen are obtained, which, in principle, can be used to create engines operating on hydrogen fuel. Of other transition metal hydrides, uranium hydride of constant composition UH 3 is of interest, which serves as a source of other high-purity uranium compounds.

Application

Hydrogen is used mainly for the production of ammonia, which is needed for the production of fertilizers and many other substances. From liquid vegetable oils, using hydrogen, solid fats are obtained, similar to butter and other animal fats. They are used in Food Industry... The production of quartz glass products requires a very high temperature. And here hydrogen is used: a burner with a hydrogen-oxygen flame gives a temperature above 2000 degrees, at which quartz melts easily.

In laboratories and in industry, the reaction of hydrogen addition to various compounds - hydrogenation - is widely used. The most common reactions are the hydrogenation of multiple carbon-carbon bonds. So, from acetylene it is possible to obtain ethylene or (with complete hydrogenation) ethane, from benzene - cyclohexane, from liquid unsaturated oleic acid - solid saturated stearic acid, etc. Other classes of organic compounds are also subjected to hydrogenation, while their reduction occurs. So, when hydrogenating carbonyl compounds (aldehydes, ketones, esters) the corresponding alcohols are formed; for example, isopropyl alcohol is obtained from acetone. When nitro compounds are hydrogenated, the corresponding amines are formed.

Hydrogenation with molecular hydrogen is often carried out in the presence of catalysts. In industry, as a rule, heterogeneous catalysts are used, which include metals of group VIII of the periodic table of elements - nickel, platinum, rhodium, palladium. The most active of these catalysts is platinum; with its help, even aromatic compounds can be hydrogenated at room temperature without pressure. The activity of cheaper catalysts can be increased by carrying out the hydrogenation reaction under pressure at elevated temperatures in special devices - autoclaves. Thus, hydrogenation of aromatic compounds on nickel requires pressures up to 200 atm and temperatures above 150 ° C.

In laboratory practice, various methods of non-catalytic hydrogenation are also widely used. One of them is the action of hydrogen at the moment of release. Such "active hydrogen" can be obtained by the reaction of metallic sodium with alcohol or amalgamated zinc with hydrochloric acid. Hydrogenation with complex hydrides - sodium borohydride NaBH 4 and lithium aluminum hydride LiAlH 4 - is widely used in organic synthesis. The reaction is carried out in anhydrous media, since complex hydrides are instantly hydrolyzed.

Hydrogen is used in many chemical laboratories. It is stored under pressure in steel cylinders, which for safety are attached to the wall with special clamps or even taken out into the yard, and the gas enters the laboratory through a thin tube.

Hydrogen is a chemical element with the symbol H and atomic number 1. With a standard atomic weight of about 1.008, hydrogen is the lightest element on the periodic table. Its monatomic form (H) is the most abundant chemical in the universe, accounting for approximately 75% of the baryon's total mass. Stars are mostly made of hydrogen in a plasma state. The most common isotope of hydrogen, called protium (this name is rarely used, the symbol 1H), has one proton and no neutrons. The ubiquitous appearance of atomic hydrogen first occurred in the era of recombination. At standard temperatures and pressures, hydrogen is a colorless, odorless, tasteless, non-toxic, non-metallic, flammable diatomic gas with the molecular formula H2. Because hydrogen readily forms covalent bonds with most non-metallic elements, most of the hydrogen on Earth exists in molecular forms such as water or organic compounds. Hydrogen plays a particularly important role in acid-base reactions because most acid-based reactions involve the exchange of protons between soluble molecules. In ionic compounds, hydrogen can take the form of a negative charge (i.e., anion), in which it is known as a hydride, or as a positively charged (i.e., cation) species denoted by the symbol H +. The hydrogen cation is described as consisting of a simple proton, but in reality, the hydrogen cations in ionic compounds are always more complex. Being the only neutral atom for which the Schrödinger equation can be solved analytically, hydrogen (namely, the study of energy and the bonding of its atom) played a key role in the development of quantum mechanics. Hydrogen gas was first produced artificially in the early 16th century by the reaction of acids with metals. In 1766-81. Henry Cavendish was the first to recognize that hydrogen gas is a discrete substance and that it produces water when it is burned, which is why it was named so: in Greek, hydrogen means "water producer." Industrial hydrogen production is mainly associated with the steam conversion of natural gas and, less commonly, more energy intensive methods such as water electrolysis. Most hydrogen is used close to where it is produced, with the two most common uses being fossil fuel processing (eg hydrocracking) and ammonia production, mainly for the fertilizer market. Hydrogen is a concern in metallurgy because it can brittle many metals, making it difficult to design pipelines and storage tanks.

Properties

Combustion

Hydrogen gas (dihydrogen or molecular hydrogen) is a flammable gas that will burn in air over a very wide concentration range from 4% to 75% by volume. The enthalpy of combustion is 286 kJ / mol:

2 H2 (g) + O2 (g) → 2 H2O (l) + 572 kJ (286 kJ / mol)

Hydrogen gas forms explosive mixtures with air in concentrations from 4-74% and with chlorine in concentrations up to 5.95%. Explosive reactions can be caused by sparks, heat or sunlight. The autoignition temperature of hydrogen, the spontaneous ignition temperature in air, is 500 ° C (932 ° F). Pure hydrogen-oxygen flames emit ultraviolet radiation and with a high oxygen mixture are almost invisible to the naked eye, as evidenced by the faint plume of the space shuttle's main engine compared to the highly visible plume of the space shuttle solid rocket amplifier that uses an ammonium perchlorate composite. A flame detector may be required to detect burning hydrogen leaks; such leaks can be very dangerous. The hydrogen flame is blue under other conditions, and resembles the blue flame of natural gas. The sinking of the Hindenburg airship is a notorious example of the burning of hydrogen, and the case is still under debate. The visible orange flame in this incident was caused by exposure to a mixture of hydrogen and oxygen combined with carbon compounds from the airship's skin. H2 reacts with every oxidizing element. Hydrogen can react spontaneously at room temperature with chlorine and fluorine to form the corresponding hydrogen halides, hydrogen chloride and hydrogen fluoride, which are also potentially hazardous acids.

Electron energy levels

The energy level of the ground state of an electron in a hydrogen atom is -13.6 eV, which is equivalent to an ultraviolet photon with a wavelength of about 91 nm. The energy levels of hydrogen can be calculated fairly accurately using Bohr's model of the atom, which conceptualizes the electron as an "orbiting" proton, similar to the Earth's orbit of the Sun. However, an atomic electron and a proton are held together by electromagnetic force, while planets and celestial objects are held together by gravity. Due to the discretization of angular momentum postulated in early quantum mechanics by Bohr, an electron in Bohr's model can only occupy certain allowable distances from the proton and therefore only certain allowable energies. A more accurate description of the hydrogen atom comes from purely quantum mechanical processing that uses the Schrödinger equation, Dirac's equation, or even the Feynman integrated circuit to calculate the probability density of an electron around a proton. The most sophisticated processing methods allow obtaining small effects of the special theory of relativity and vacuum polarization. In quantum machining, an electron in a hydrogen atom has no ground state at all torque, which illustrates how a "planetary orbit" differs from the motion of an electron.

Elementary molecular forms

There are two different spin isomers of diatomic hydrogen molecules, which differ in the relative spin of their nuclei. In orthohydrogen form, the spins of the two protons are parallel and form a triplet state with a molecular spin quantum number of 1 (1/2 + 1/2); in the form of parahydrogen, the spins are antiparallel and form a singlet with the molecular spin quantum number 0 (1/2 1/2). At standard temperature and pressure, hydrogen gas contains about 25% para-form and 75% ortho-form, also known as "normal form". The equilibrium ratio of orthohydrogen to parahydrogen depends on temperature, but since the ortho-form is an excited state and has a higher energy than the para-form, it is unstable and cannot be purified. At very low temperatures, the state of equilibrium consists almost exclusively of the para-form. The thermal properties of the liquid and gas phases of pure parahydrogen differ significantly from the properties of the normal form due to differences in the rotational heat capacities, which is discussed in more detail in the spin isomers of hydrogen. The ortho / pair difference also occurs in other hydrogen-containing molecules or functional groups such as water and methylene, but this is of little consequence to their thermal properties. The uncatalyzed interconversion between vapor and ortho H2 increases with increasing temperature; thus, the rapidly condensed H2 contains large amounts of the high energy orthogonal form, which is very slowly converted to the para form. The ortho / vapor ratio in condensed H2 is an important factor in the preparation and storage of liquid hydrogen: the conversion from ortho to vapor is exothermic and provides enough heat to vaporize some of the hydrogen liquid, resulting in the loss of liquefied material. Ortho-para conversion catalysts such as iron oxide, activated carbon, platinized asbestos, rare earth metals, uranium compounds, chromium oxide or some nickel compounds are used for cooling with hydrogen.

Phases

Hydrogen gas

Liquid hydrogen

Slime hydrogen

Solid hydrogen

Metallic hydrogen

Connections

Covalent and organic compounds

While H2 is not very reactive under standard conditions, it forms compounds with most elements. Hydrogen can form compounds with elements that are more electronegative, such as halogens (eg F, Cl, Br, I) or oxygen; in these compounds, hydrogen takes on a partial positive charge. When bonded with fluorine, oxygen, or nitrogen, hydrogen can participate in the form of a medium-strength non-covalent bond with other similar molecules, a phenomenon called hydrogen bonding that is critical to the stability of many biological molecules. Hydrogen also forms compounds with less electronegative elements such as metals and metalloids, where it takes on a partial negative charge. These compounds are often known as hydrides. Hydrogen forms a vast array of compounds with carbon, called hydrocarbons, and an even greater variety of compounds with heteroatoms, which, because of their common bond with living things, are called organic compounds. Their properties are studied in organic chemistry, and their study in the context of living organisms is known as biochemistry. According to some definitions, "organic" compounds must contain only carbon. However, most of them also contain hydrogen, and because it is the carbon-hydrogen bond that gives this class of compounds most of their specific chemical characteristics, carbon-hydrogen bonds are required in some definitions of the word "organic" in chemistry. Millions of hydrocarbons are known and are usually formed by complex synthetic pathways that rarely involve elemental hydrogen.

Hydrides

Hydrogen compounds are often referred to as hydrides. The term "hydride" implies that the H atom has acquired a negative or anionic character, designated H-, and is used when hydrogen forms a compound with a more electropositive element. The existence of a hydride anion, proposed by Gilbert N. Lewis in 1916 for salt-containing hydrides of groups 1 and 2, was demonstrated by Moers in 1920 by electrolysis of molten lithium hydride (LiH), producing a stoichiometric amount of hydrogen per anode. For hydrides other than Group 1 and 2 metals, this term is misleading given the low electronegativity of hydrogen. An exception in Group 2 hydrides is BeH2, which is polymeric. In lithium aluminum hydride, the AlH-4 anion carries hydride centers firmly attached to Al (III). Although hydrides can be formed in almost all elements of the basic group, the number and combination of possible compounds vary greatly; for example, more than 100 binary borane hydrides and only one binary aluminum hydride are known. Binary indium hydride has not yet been identified, although large complexes exist. In inorganic chemistry, hydrides can also serve as bridging ligands that bind two metal centers in a coordination complex. This function is especially characteristic for elements of group 13, especially in boranes (boron hydrides) and aluminum complexes, as well as in clustered carboranes.

Protons and acids

Oxidation of hydrogen removes its electron and gives H +, which does not contain electrons and a nucleus, which usually consists of one proton. This is why H + is often referred to as a proton. This view is central to the discussion of acids. According to the Bronsted-Lowry theory, acids are proton donors, and bases are proton acceptors. A naked proton, H +, cannot exist in solution or in ionic crystals due to its irresistible attraction to other atoms or molecules with electrons. Except for the high temperatures associated with plasma, such protons cannot be removed from the electron clouds of atoms and molecules and will remain attached to them. However, the term "proton" is sometimes used metaphorically to refer to positively charged or cationic hydrogen attached to other species in this way, and as such is referred to as “H +” without any meaning that any individual protons exist freely as a species. To avoid the appearance of a naked "solvated proton" in solution, acidic aqueous solutions are sometimes thought to contain a less unlikely fictitious species called "hydronium ion" (H 3 O +). However, even in this case, such solvated hydrogen cations are more realistically perceived as organized clusters that form species close to H 9O + 4. Other oxonium ions are found when water is in acidic solution with other solvents. Although exotic on Earth, one of the most abundant ions in the Universe is H + 3, known as protonated molecular hydrogen or trihydrogen cation.

Isotopes

Hydrogen has three naturally occurring isotopes, designated 1H, 2H, and 3H. Other highly unstable nuclei (from 4H to 7H) have been synthesized in the laboratory, but have not been observed in nature. 1H is the most abundant hydrogen isotope with a prevalence of over 99.98%. Since the nucleus of this isotope consists of only one proton, it is given a descriptive but rarely used formal name protium. 2H, another stable isotope of hydrogen, is known as deuterium and contains one proton and one neutron in its nucleus. It is believed that all the deuterium in the universe was produced during the Big Bang and has existed since that time. Deuterium is not a radioactive element and does not pose a significant toxicity hazard. Water enriched with molecules that include deuterium instead of normal hydrogen is called heavy water. Deuterium and its compounds are used as a non-radioactive label in chemical experiments and in solvents for 1H-NMR spectroscopy. Heavy water is used as a neutron moderator and as a coolant for nuclear reactors. Deuterium is also a potential fuel for commercial nuclear fusion. 3H is known as tritium and contains one proton and two neutrons in its nucleus. It is radioactive, decays into helium-3 through beta decay with a half-life of 12.32 years. It is so radioactive that it can be used in luminous paint, which makes it useful in making watches with a luminous dial, for example. The glass prevents a small amount of radiation from escaping. Not a large number of tritium is formed naturally by the interaction of cosmic rays with atmospheric gases; tritium was also released during testing nuclear weapons... It is used in nuclear fusion reactions as an indicator of isotope geochemistry and in specialized self-powered lighting devices. Tritium has also been used in chemical and biological labeling experiments as a radioactive label. Hydrogen is the only element that has different names for its isotopes, which are widely used today. During the early study of radioactivity, various heavy radioactive isotopes were given their own names, but such names are no longer used, with the exception of deuterium and tritium. The symbols D and T (instead of 2H and 3H) are sometimes used for deuterium and tritium, but the corresponding symbol for protium P is already used for phosphorus and is therefore not available for protium. In its nomenclature guidelines, the International Union of Pure and Applied Chemistry allows the use of any characters from D, T, 2H and 3H, although 2H and 3H are preferred. The exotic muonium atom (symbol Mu), made up of an anti-muon and an electron, is also sometimes regarded as a light radioisotope of hydrogen due to the mass difference between the anti-muon and an electron, which was discovered in 1960. During the lifetime of a muon, 2.2 μs, muonium can enter into compounds such as muonium chloride (MuCl) or sodium muonide (NaMu), similarly to hydrogen chloride and sodium hydride, respectively.

History

Discovery and use

In 1671, Robert Boyle discovered and described the reaction between iron filings and dilute acids, which leads to the production of hydrogen gas. In 1766, Henry Cavendish was the first to recognize hydrogen gas as a discrete substance, calling this gas "flammable air" due to its metal-acid reaction. He suggested that "flammable air" was virtually identical to a hypothetical substance called "phlogiston" and again discovered in 1781 that gas produces water when burned. It is believed that it was he who discovered hydrogen as an element. In 1783, Antoine Lavoisier named this element hydrogen (from the Greek ὑδρο-hydro meaning water and -γενής genes, meaning creator), when he and Laplace reproduced Cavendish's data that burning hydrogen produces water. Lavoisier produced hydrogen for his mass conservation experiments by reacting a stream of steam with metallic iron through an incandescent lamp heated in a fire. Anaerobic oxidation of iron by protons of water at high temperatures can be schematically represented by a set of the following reactions:

Fe + H2O → FeO + H2

2 Fe + 3 H2O → Fe2O3 + 3 H2

3 Fe + 4 H2O → Fe3O4 + 4 H2

Many metals, such as zirconium, undergo a similar reaction with water to produce hydrogen. The hydrogen was first liquefied by James Dewar in 1898 using regenerative refrigeration and his invention, the vacuum flask. The following year, he produced solid hydrogen. Deuterium was discovered in December 1931 by Harold Urey, and tritium was prepared in 1934 by Ernest Rutherford, Mark Oliphant, and Paul Harteck. Heavy water, which consists of deuterium instead of ordinary hydrogen, was discovered by Yurey's group in 1932. François Isaac de Rivaz built the first Rivaz engine, an internal combustion engine powered by hydrogen and oxygen, in 1806. Edward Daniel Clarke invented the hydrogen gas tube in 1819. The Doebereiner Flame (the first full-fledged lighter) was invented in 1823. The first hydrogen cylinder was invented by Jacques Charles in 1783. Hydrogen provided the rise of the first reliable form of air traffic after the invention of Henri Giffard's first hydrogen-powered airship in 1852. The German Count Ferdinand von Zeppelin promoted the idea of ​​rigid airships lifted into the air by hydrogen, which were later called the Zeppelin; the first of these took off for the first time in 1900. Regularly scheduled flights began in 1910 and by the outbreak of World War I in August 1914, they had carried 35,000 passengers without major incident. During the war, hydrogen airships were used as observation platforms and bombers. The first non-stop transatlantic flight was made by the British R34 airship in 1919. Regular passenger service resumed in the 1920s and the discovery of stocks of helium in the United States was supposed to improve flight safety, but the US government refused to sell gas for this purpose, so H2 was used in the Hindenburg airship, which was destroyed in a fire in Milan in New Jersey May 6, 1937 The incident was broadcast live on radio and filmed. It has been widely speculated that the ignition was due to a hydrogen leak, but subsequent research indicates that the aluminized fabric covering could ignite with static electricity. But by this time, hydrogen's reputation as a lift gas had already been damaged. In the same year, the first hydrogen-cooled turbine generator with hydrogen gas as the refrigerant in the rotor and stator entered service in 1937 in Dayton, Ohio, by Dayton Power & Light Co; Due to the thermal conductivity of hydrogen gas, it is the most common gas for use in this field today. The nickel-hydrogen battery was first used in 1977 aboard the US Navigation Technology Satellite 2 (NTS-2). The ISS, Mars Odyssey and Mars Global Surveyor are all powered by nickel-hydrogen batteries. In the dark part of its orbit, the Hubble Space Telescope is also powered by nickel-hydrogen batteries that were finally replaced in May 2009, more than 19 years after launch and 13 years after their design.

Role in quantum theory

Because of its simple atomic structure, consisting only of a proton and an electron, the hydrogen atom, together with the spectrum of light created from or absorbed by it, has been central to the development of the theory of atomic structure. In addition, the study of the corresponding simplicity of the hydrogen molecule and the corresponding H + 2 cation led to an understanding of the nature of the chemical bond, which soon followed the physical treatment of the hydrogen atom in quantum mechanics in mid-2020.One of the first quantum effects that were clearly observed (but were not understood at the time), there was Maxwell's observation of hydrogen half a century before the full quantum mechanical theory emerged. Maxwell noted that the specific heat of H2 irreversibly departs from a diatomic gas below room temperature and begins to increasingly resemble the specific heat of a monatomic gas at cryogenic temperatures. According to quantum theory, this behavior arises from the distance of the (quantized) levels of rotational energy, which are especially widely spaced in H2 due to its low mass. These widely spaced levels prevent an equal division of thermal energy into rotational motion in hydrogen at low temperatures. Diatom gases, which are made up of heavier atoms, do not have such widely spaced levels and do not exhibit the same effect. Antihydrogen is an antimaterial analogue of hydrogen. It consists of an antiproton with a positron. Antihydrogen is the only type of antimatter atom that has been produced as of 2015.

Being in nature

Hydrogen is the most abundant chemical element in the Universe, accounting for 75% of normal matter by mass and over 90% by the number of atoms. (Most of the mass in the universe, however, is not in the form of this chemical element, but is believed to have as yet undiscovered forms of mass, such as dark matter and dark energy.) This element is found in great abundance in stars and gas giants. Molecular H2 clouds are associated with star formation. Hydrogen plays a vital role in turning stars on through the proton-proton reaction and nuclear fusion of the CNO cycle. All over the world, hydrogen is found mainly in atomic and plasma states with properties quite different from those of molecular hydrogen. As a plasma, the electron and proton of hydrogen are not bonded to each other, resulting in very high electrical conductivity and high emissivity (generating light from the sun and other stars). Charged particles are strongly influenced by magnetic and electric fields. For example, in the solar wind, they interact with the Earth's magnetosphere, creating Birkeland currents and auroras. Hydrogen is in a neutral atomic state in the interstellar medium. It is believed that large amounts of neutral hydrogen found in damped Lyman-alpha systems dominate the cosmological baryon density of the Universe up to redshift z = 4. Under normal conditions on Earth, elemental hydrogen exists as a diatomic gas, H2. However, hydrogen gas is very rare in the earth's atmosphere (1 ppm by volume) due to its light weight, which makes it easier to overcome Earth's gravity than heavier gases. However, hydrogen is the third most abundant element on the Earth's surface, existing primarily in the form of chemical compounds such as hydrocarbons and water. Hydrogen gas is produced by some bacteria and algae and is a natural component of flute, just like methane, which is an increasingly important source of hydrogen. A molecular form called protonated molecular hydrogen (H + 3) is found in the interstellar medium, where it is generated by ionizing molecular hydrogen from cosmic rays. This charged ion has also been observed in the upper atmosphere of the planet Jupiter. Ion is relatively stable in the environment due to its low temperature and density. H + 3 is one of the most abundant ions in the Universe and plays a prominent role in the chemistry of the interstellar medium. Neutral triatomic hydrogen H3 can exist only in an excited form and is unstable. In contrast, the positive molecular ion of hydrogen (H + 2) is a rare molecule in the universe.

Hydrogen production

H2 is produced in chemical and biological laboratories, often as a by-product of other reactions; in industry for the hydrogenation of unsaturated substrates; and in nature as a means of displacing reducing equivalents in biochemical reactions.

Steam reforming

Hydrogen can be obtained in several ways, but economically the most important processes include the removal of hydrogen from hydrocarbons, as about 95% of hydrogen production in 2000 came from steam reforming. Commercially, large volumes of hydrogen are typically produced by steam reforming of natural gas. At high temperatures (1000-1400 K, 700-1100 ° C, or 1300-2000 ° F), steam (water vapor) reacts with methane to produce carbon monoxide and H2.

CH4 + H2O → CO + 3 H2

This reaction works best at low pressures, but nevertheless, it can be carried out at high pressures (2.0 MPa, 20 atm or 600 inches of mercury). This is because high pressure H2 is the most popular product and pressure superheat cleaning systems perform better at higher pressures. The product mixture is known as "syngas" because it is often used directly to produce methanol and related compounds. Hydrocarbons other than methane can be used to produce synthesis gas with different product ratios. One of the many complications of this highly optimized technology is the formation of coke or carbon:

CH4 → C + 2 H2

Consequently, steam reforming typically uses excess H2O. Additional hydrogen can be recovered from the steam using carbon monoxide through a water gas displacement reaction, especially using an iron oxide catalyst. This reaction is also a common industrial source of carbon dioxide:

CO + H2O → CO2 + H2

Other important methods for H2 include partial oxidation of hydrocarbons:

2 CH4 + O2 → 2 CO + 4 H2

And the reaction of coal, which may serve as a prelude to the shear reaction described above:

C + H2O → CO + H2

Sometimes hydrogen is produced and consumed in the same industrial process, without separation. In the Haber process for the production of ammonia, hydrogen is generated from natural gas. Brine electrolysis to produce chlorine also produces hydrogen as a by-product.

Metallic acid

In the laboratory, H2 is usually produced by reacting dilute non-oxidizing acids with some reactive metals such as zinc with a Kipp apparatus.

Zn + 2 H + → Zn2 + + H2

Aluminum can also produce H2 when treated with bases:

2 Al + 6 H2O + 2 OH- → 2 Al (OH) -4 + 3 H2

Water electrolysis is an easy way to produce hydrogen. A low voltage current flows through the water and oxygen gas is generated at the anode, while hydrogen gas is generated at the cathode. Typically, the cathode is made from platinum or another inert metal in the production of hydrogen for storage. If, however, the gas is to be burnt in situ, the presence of oxygen is desirable to promote combustion, and therefore both electrodes will be made of inert metals. (For example, iron is oxidized and therefore reduces the amount of oxygen released.) The theoretical maximum efficiency (electricity used in relation to the energy value of hydrogen produced) is in the range of 80-94%.

2 H2O (L) → 2 H2 (g) + O2 (g)

An alloy of aluminum and gallium in the form of granules added to water can be used to produce hydrogen. This process also produces aluminum oxide, but the expensive gallium, which prevents the formation of oxide skin on the granules, can be reused. This has important potential implications for the hydrogen economy, as hydrogen can be produced locally and does not need to be transported.

Thermochemical properties

There are over 200 thermochemical cycles that can be used to separate water, about a dozen of these cycles, such as the iron oxide cycle, cerium (IV) oxide cycle, cerium (III) oxide, zinc oxide zinc, sulfur iodine cycle, copper cycle, etc. chlorine and the hybrid sulfur cycle are in the research and testing stages to produce hydrogen and oxygen from water and heat without the use of electricity. A number of laboratories (including those in France, Germany, Greece, Japan and the USA) are developing thermochemical methods for producing hydrogen from solar energy and water.

Anaerobic corrosion

Under anaerobic conditions, iron and steel alloys are slowly oxidized by the protons of water, while being reduced in molecular hydrogen (H2). Anaerobic corrosion of iron leads first to the formation of iron hydroxide (green rust) and can be described by the following reaction: Fe + 2 H2O → Fe (OH) 2 + H2. In turn, under anaerobic conditions, iron hydroxide (Fe (OH) 2) can be oxidized by water protons to form magnetite and molecular hydrogen. This process is described by the Shikorr reaction: 3 Fe (OH) 2 → Fe3O4 + 2 H2O + H2 iron hydroxide → magnesium + water + hydrogen. Well-crystallized magnetite (Fe3O4) is thermodynamically more stable than iron hydroxide (Fe (OH) 2). This process takes place during the anaerobic corrosion of iron and steel in anoxic groundwater and during the restoration of soils below the water table.

Geological origin: serpentinization reaction

In the absence of oxygen (O2) in deep geological conditions prevailing far from the Earth's atmosphere, hydrogen (H2) is formed in the process of serpentinization by anaerobic oxidation of iron silicate (Fe2 +) by water protons (H +) present in the crystal lattice of fayalite (Fe2SiO4, minal olivine -gland). The corresponding reaction leading to the formation of magnetite (Fe3O4), quartz (SiO2) and hydrogen (H2): 3Fe2SiO4 + 2 H2O → 2 Fe3O4 + 3 SiO2 + 3 H2 fayalite + water → magnetite + quartz + hydrogen. This reaction is very similar to the Schikorr reaction observed during the anaerobic oxidation of iron hydroxide in contact with water.

Formation in transformers

Of all the hazardous gases produced in power transformers, hydrogen is the most abundant and generated in most fault conditions; thus, the formation of hydrogen is an early sign of serious problems in the life cycle of a transformer.

Applications

Consumption in various processes

Large amounts of H2 are required in the petroleum and chemical industries. Mostly, H2 is used for the processing ("modernization") of fossil fuels and for the production of ammonia. In petrochemical plants, H2 is used in hydrodealkylation, hydrodesulfurization, and hydrocracking. H2 has several other important uses. H2 is used as a hydrogenating agent, in particular to increase the saturation level of unsaturated fats and oils (found in items such as margarine) and in the production of methanol. It is also a source of hydrogen in production of hydrochloric acid... H2 is also used as a reducing agent for metal ores. Hydrogen is highly soluble in many rare earth and transition metals and is soluble in both nanocrystalline and amorphous metals. The solubility of hydrogen in metals depends on local distortions or impurities in the crystal lattice. This can be useful when hydrogen is purified by passing through hot palladium discs, but the high solubility of the gas is a metallurgical problem, contributing to the embrittlement of many metals, complicating the design of pipelines and storage tanks. In addition to being used as a reagent, H2 has a wide range of applications in physics and technology. It is used as a shielding gas in welding methods such as hydrogen atomic welding. H2 is used as a rotor coolant in electric generators in power plants because it has the highest thermal conductivity of all gases. Liquid H2 is used in cryogenic research, including superconductivity research. Since H2 is lighter than air, at just over 1/14 of the density of air, it was once widely used as a lift gas in balloons and airships. In newer applications, hydrogen is used neat or mixed with nitrogen (sometimes called forming gas) as an indicator gas for instantaneous leak detection. Hydrogen is used in the automotive, chemical, energy, aerospace and telecommunications industries. Hydrogen is a permitted food supplement(E 949), which allows leak testing of foodstuffs, in addition to other antioxidant properties. Rare isotopes of hydrogen also have specific uses. Deuterium (hydrogen-2) is used in nuclear fission applications as a slow neutron moderator and in nuclear fusion reactions. Deuterium compounds are used in the field of chemistry and biology to study the isotope effects of a reaction. Tritium (hydrogen-3), produced in nuclear reactors, is used in the manufacture of hydrogen bombs, as an isotope marker in the biological sciences, and as a radiation source in glowing paints. The triple point of equilibrium hydrogen is the defining fixed point in the ITS-90 temperature scale at 13.8033 Kelvin.

Cooling medium

Hydrogen is commonly used in power plants as a refrigerant in generators due to a number of beneficial properties that are a direct result of its light diatomic molecules. These include low density, low viscosity and the highest specific heat and thermal conductivity of all gases.

Energy carrier

Hydrogen is not an energy resource, except in the hypothetical context of commercial fusion power plants using deuterium or tritium, and this technology is currently far from being developed. The energy of the Sun comes from the nuclear fusion of hydrogen, but this process is difficult to achieve on Earth. Elemental hydrogen from solar, biological, or electrical sources requires more energy to produce it than is consumed when burning it, so in these cases hydrogen functions as an energy carrier, by analogy with a battery. Hydrogen can be obtained from fossil sources (such as methane), but these sources are depleted. The energy density per unit volume of both liquid hydrogen and compressed hydrogen gas at any practically achievable pressure is significantly less than that of traditional energy sources, although the energy density per unit mass of fuel is higher. However, elemental hydrogen has been widely discussed in the energy context as a possible future energy carrier for the entire economy. For example, CO2 sequestration followed by carbon capture and storage can be carried out at the point of production of H2 from fossil fuels. The hydrogen used in transportation will burn relatively cleanly, with some NOx emissions, but no carbon emissions. However, the infrastructure cost associated with a full conversion to a hydrogen economy will be substantial. Fuel cells can convert hydrogen and oxygen directly into electricity more efficiently than internal combustion engines.

Semiconductor industry

Hydrogen is used to saturate the dangling bonds of amorphous silicon and amorphous carbon, which helps stabilize material properties. It is also a potential electron donor in various oxide materials including ZnO, SnO2, CdO, MgO, ZrO2, HfO2, La2O3, Y2O3, TiO2, SrTiO3, LaAlO3, SiO2, Al2O3, ZrSiO4, HfSiO4, and SrZrO3.

Biological reactions

H2 is a product of several types of anaerobic metabolism and is produced by several microorganisms, usually through reactions catalyzed by iron or nickel-containing enzymes called hydrogenases. These enzymes catalyze a reversible redox reaction between H2 and its components, two protons and two electrons. The creation of hydrogen gas occurs by transferring the reducing equivalents formed during the fermentation of pyruvate into water. The natural cycle of production and consumption of hydrogen by organisms is called the hydrogen cycle. Water splitting, the process by which water breaks down into its constituent protons, electrons and oxygen, occurs in light reactions in all photosynthetic organisms. Several such organisms, including the algae Chlamydomonas Reinhardtii and cyanobacteria, have developed a second stage in dark reactions in which protons and electrons are reduced to form H2 gas by specialized hydrogenases in the chloroplast. Attempts have been made to genetically modify cyanobacterial hydrases to efficiently synthesize H2 gas even in the presence of oxygen. Efforts have also been made using genetically modified algae in a bioreactor.

The most abundant chemical element in the Universe is hydrogen. This is a kind of starting point, because in the periodic table, its atomic number is equal to one. Humanity hopes to be able to learn more about it as one of the most possible Vehicle in the future. Hydrogen is the simplest, lightest, most widespread element, there is a lot of it everywhere - seventy-five percent of the total mass of matter. It is found in any star, especially a lot of hydrogen in gas giants. Its role in stellar fusion reactions is key. Without hydrogen, there is no water, which means there is no life. Everyone remembers that a water molecule contains one oxygen atom, and two atoms in it - hydrogen. This is the well-known formula H 2 O.

How we use it

Discovered hydrogen in 1766 by Henry Cavendish when he was analyzing the oxidation reaction of a metal. After several years of observation, he realized that in the process of burning hydrogen, water is formed. Previously, scientists isolated this element, but did not consider it independent. In 1783, hydrogen received the name hydrogen (translated from the Greek "hydro" - water, and "gene" - to give birth). The element that generates water is hydrogen. It is a gas whose molecular formula is H 2. If the temperature is close to room temperature, and the pressure is normal, this element is imperceptible. Hydrogen may not even be caught by human senses - it is tasteless, colorless, odorless. But under pressure and at a temperature of -252.87 C (very cold!), This gas liquefies. This is how it is stored, since it takes up much more space in the form of gas. It is liquid hydrogen that is used as propellant.

Hydrogen can become solid, metallic, but this requires ultra-high pressure, and this is what the most prominent scientists - physicists and chemists - are doing now. This element is already serving as an alternative fuel for transport. Its use is similar to how an internal combustion engine works: when hydrogen is burned, a lot of its chemical energy is released. A method for creating a fuel cell based on it has also been practically developed: when combined with oxygen, a reaction occurs, and through this, water and electricity are formed. Perhaps, soon transport will "switch" instead of gasoline to hydrogen - a lot of car manufacturers are interested in the creation of alternative combustible materials, there are also successes. But a purely hydrogen engine is still in the future, there are many difficulties here. However, the advantages are such that the creation of a fuel tank with solid hydrogen is in full swing, and scientists and engineers are not going to retreat.

Basic information

Hydrogenium (lat.) - hydrogen, the first serial number in the periodic table, denoted by H. The hydrogen atom has a mass of 1.0079, it is a gas that under normal conditions has neither taste, nor smell, nor color. Chemists since the sixteenth century have described a certain combustible gas with different names. But it turned out for everyone under the same conditions - when an acid acts on the metal. For many years, hydrogen was simply called "combustible air" by the Cavendish himself. Only in 1783 Lavoisier proved that water has a complex composition, through synthesis and analysis, and four years later he gave the "combustible air" his modern name... The root of this compound word it is widely used when it is necessary to name the compounds of hydrogen and any processes in which it participates. For example, hydrogenation, hydride, and the like. And the Russian name was proposed in 1824 by M. Solovyov.

In nature, the distribution of this element is unmatched. In the lithosphere and hydrosphere of the earth's crust, its mass is one percent, but hydrogen atoms are as much as sixteen percent. The most widespread on Earth is water, and 11.19% by mass in it is hydrogen. It is also invariably present in almost all compounds of which oil, coal, all natural gases, and clay are composed. There is hydrogen in all organisms of plants and animals - in the composition of proteins, fats, nucleic acids, carbohydrates, and so on. The free state for hydrogen is not typical and almost never occurs - there is very little of it in natural and volcanic gases. An absolutely insignificant amount of hydrogen in the atmosphere - 0.0001%, by the number of atoms. On the other hand, whole streams of protons represent hydrogen in near-earth space, it consists of the inner radiation belt of our planet.

Space

In space, no element occurs as often as hydrogen. The volume of hydrogen in the composition of the elements of the Sun is more than half of its mass. Most stars form hydrogen, which is in the form of plasma. The bulk of the various gases in nebulae and in the interstellar medium also consist of hydrogen. It is present in comets, in the atmosphere of a number of planets. Naturally, not in pure form, either as free H 2, then as methane CH 4, then as ammonia NH 3, even as water H 2 O. The radicals CH, NH, SiN, OH, PH and the like are very common. As a flux of protons, hydrogen is part of the corpuscular solar radiation and cosmic rays.

In ordinary hydrogen, a mixture of two stable isotopes is light hydrogen (or protium 1 H) and heavy hydrogen (or deuterium - 2 H or D). There are other isotopes: radioactive tritium - 3 H or T, otherwise - superheavy hydrogen. And also very unstable 4 N. In nature, a hydrogen compound contains isotopes in the following proportions: there are 6800 protium atoms per deuterium atom. Tritium is formed in the atmosphere from nitrogen, which is influenced by cosmic ray neutrons, but is negligible. What do isotope mass numbers stand for? The figure indicates that the protium nucleus has only one proton, while deuterium has not only a proton in the atomic nucleus, but also a neutron. Tritium in the nucleus has two neutrons to one proton. But 4 N contains three neutrons per proton. Therefore, the physical properties and chemical properties of hydrogen isotopes are very different in comparison with isotopes of all other elements - the difference in masses is too large.

Structure and physical properties

The structure of the hydrogen atom is the simplest in comparison with all other elements: one nucleus - one electron. Ionization potential - the binding energy of a nucleus with an electron - 13.595 electron volts (eV). It is because of the simplicity of this structure that the hydrogen atom is convenient as a model in quantum mechanics when it is necessary to calculate the energy levels of more complex atoms. In the H2 molecule there are two atoms that are linked by a chemical covalent bond. The decay energy is very high. Atomic hydrogen can be formed in chemical reactions such as zinc and hydrochloric acid. However, there is practically no interaction with hydrogen - the atomic state of hydrogen is very short, the atoms immediately recombine into H2 molecules.

From a physical point of view, hydrogen is lighter than all known substances - more than fourteen times lighter than air (remember the balloons flying away at the holidays - they have just hydrogen inside them). However, it can boil, liquefy, melt, solidify, and only helium boils and melts at lower temperatures. It is difficult to liquefy it, you need a temperature below -240 degrees Celsius. But it has a very high thermal conductivity. It almost does not dissolve in water, but the interaction with the hydrogen of metals is excellent - it dissolves in almost all, best of all in palladium (one volume of hydrogen takes eight hundred and fifty volumes). Liquid hydrogen is light and fluid, and when it dissolves in metals, it often destroys alloys due to interaction with carbon (steel, for example), diffusion and decarbonization occurs.

Chemical properties

In compounds, for the most part, hydrogen shows an oxidation state (valence) of +1, like sodium and other alkali metals. He is considered as their analogue, standing at the head of the first group of the Mendeleev system. But the hydrogen ion in metal hydrides is negatively charged, with an oxidation state of -1. Also, this element is close to halogens, which are even capable of replacing it in organic compounds. This means that hydrogen can be attributed to the seventh group of the Mendeleev system. Under normal conditions, hydrogen molecules do not differ in activity, combining only with the most active non-metals: good with fluorine, and if light - with chlorine. But when heated, hydrogen becomes different - it reacts with many elements. Compared to molecular hydrogen, atomic hydrogen is very active chemically, because in connection with oxygen, water is formed, and energy and heat are released along the way. At room temperature, this reaction is very slow, but when heated above five hundred and fifty degrees, an explosion occurs.

Hydrogen is used to reduce metals, because it takes oxygen away from their oxides. With fluorine, hydrogen forms an explosion even in the dark and at minus two hundred and fifty-two degrees Celsius. Chlorine and bromine excite hydrogen only when heated or illuminated, and iodine only when heated. Hydrogen with nitrogen forms ammonia (this is how most fertilizers are produced). When heated, it very actively interacts with sulfur, and hydrogen sulfide is obtained. Tellurium and selenium are difficult to react with hydrogen, but pure carbon reacts at very high temperatures to produce methane. With carbon monoxide, hydrogen forms various organic compounds, here pressure, temperature, catalysts affect, and all this is of great practical importance. And in general, the role of hydrogen, as well as of its compounds, is exceptionally great, since it gives acidic properties to protic acids. A hydrogen bond is formed with many elements, which affects the properties of both inorganic and organic compounds.

Receiving and using

Hydrogen is obtained on an industrial scale from natural gases - combustible, coke oven, petroleum refining gases. It can also be obtained by electrolysis where electricity is not too expensive. However, the most important method of hydrogen production is the catalytic interaction of hydrocarbons, mostly methane, with steam when conversion is obtained. The method of oxidation of hydrocarbons with oxygen is also widely used. Extraction of hydrogen from natural gas is the cheapest method. The other two are the use of coke oven gas and refinery gas - hydrogen is released when the remaining components are liquefied. They lend themselves more easily to liquefaction, and for hydrogen, as we remember, you need -252 degrees.

Hydrogen peroxide is very popular in use. Treatment with this solution is used very often. The molecular formula H 2 O 2 is unlikely to be named by all those millions of people who want to be blondes and lighten their hair, as well as those who love cleanliness in the kitchen. Even those who treat scratches from playing with a kitten often do not realize that they are using hydrogen treatment. But everyone knows the story: since 1852, hydrogen has been used for a long time in aeronautics. The airship, invented by Henry Giffard, was based on hydrogen. They were called zeppelins. The rapid development of aircraft construction drove the zeppelins out of the sky. In 1937, there was a major accident when the Hindenburg airship burned down. After this incident, zeppelins were never used again. But at the end of the eighteenth century, the spread of balloons filled with hydrogen was widespread. In addition to the production of ammonia, today hydrogen is required for the manufacture of methyl alcohol and other alcohols, gasoline, hydrogenated heavy fuel oils and solid fuels. You cannot do without hydrogen when welding, when cutting metals - it can be oxygen-hydrogen and atomic-hydrogen. And tritium and deuterium give life to nuclear power. These are, as we remember, isotopes of hydrogen.

Neumyvakin

Hydrogen as a chemical element is so good that it could not help but have its own fans. Ivan Pavlovich Neumyvakin is a doctor of medical sciences, professor, laureate of the State Prize and he has many more titles and awards, among them. As a traditional medicine doctor, he was named the best folk healer in Russia. It was he who developed many methods and principles of providing medical assistance to astronauts in flight. It was he who created a unique hospital - a hospital on board a spacecraft. At the same time, he was the state coordinator for the field of cosmetic medicine. Space and cosmetics. His passion for hydrogen is not aimed at making big money, as is now the case in domestic medicine, but on the contrary - to teach people to cure anything from literally a penny means, without additional visits to pharmacies.

He promotes treatment with a drug that is present in literally every home. This is hydrogen peroxide. You can criticize Neumyvakin as much as you like, he will still insist on his own: yes, indeed, literally everything can be cured with hydrogen peroxide, because it saturates the internal cells of the body with oxygen, destroys toxins, normalizes acid and alkaline balance, and from here tissues are regenerated, the whole organism. So far, no one has seen the cured with hydrogen peroxide, much less examined, but Neumyvakin claims that using this remedy, you can completely get rid of viral, bacterial and fungal diseases, prevent the development of tumors and atherosclerosis, defeat depression, rejuvenate the body and never get sick SARS and colds.

Panacea

Ivan Pavlovich is sure that with the correct use of this simplest drug and observing all the simple instructions, you can defeat many diseases, including very serious ones. Their list is huge: from periodontal disease and tonsillitis to myocardial infarction, strokes and diabetes mellitus. Such trifles as sinusitis or osteochondrosis fly away from the first treatment sessions. Even cancerous tumors get scared and flee from hydrogen peroxide, because immunity is stimulated, the life of the body and its defenses are activated.

Even children can be treated in this way, except that it is better for pregnant women to refrain from using hydrogen peroxide for now. Also, this method is not recommended for people with transplanted organs due to possible tissue incompatibility. The dosage should be strictly observed: from one drop to ten, adding one every day. Three times a day (thirty drops of a three percent hydrogen peroxide solution per day, wow!) Half an hour before meals. The solution can be administered intravenously and under medical supervision. Sometimes hydrogen peroxide is combined for a more powerful effect with other drugs. Inside, the solution is used only in a diluted form - with clean water.

Outwardly

Compresses and rinses, even before Professor Neumyvakin created his methods, were very popular. Everyone knows that, just like alcohol compresses, hydrogen peroxide cannot be used in its pure form, because it will burn tissues, but warts or fungal lesions are lubricated locally and with a strong solution - up to fifteen percent.

For skin rashes, for headaches, procedures are also performed in which hydrogen peroxide is involved. The compress should be done with a cotton cloth dipped in a solution of two teaspoons of three percent hydrogen peroxide and fifty milligrams of pure water. Cover the fabric with foil and wrap with wool or a towel. The time of action of the compress is from a quarter of an hour to an hour and a half in the morning and in the evening until recovery.

Opinion of doctors

Opinions are divided, not everyone is amazed by the properties of hydrogen peroxide, moreover, they are not only not believed, they are laughed at. Among the doctors are also those who supported Neumyvakin and even picked up the development of his theory, but they are in the minority. Most doctors consider such a treatment plan not only ineffective, but also often destructive.

Indeed, there is not yet a single officially proven case when a patient would have been cured with hydrogen peroxide. At the same time, there is no information about the deterioration of health in connection with the use of this method. But precious time is lost, and a person who has received one of the serious illnesses and has completely relied on Neumyvakin's panacea runs the risk of being late for the start of his real traditional treatment.

In the periodic table, it has its definite place of position, which reflects the properties manifested by it and speaks of its electronic structure. However, there is one special atom among all, which occupies two cells at once. It is located in two groups of elements that are completely opposite in terms of manifested properties. This is hydrogen. These features make it unique.

Hydrogen is not just an element, but also a simple substance, as well as a component of many complex compounds, a biogenic and organogenic element. Therefore, we will 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, respectively, the number of protons is the same. The atomic mass is 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 the outside allows it to successfully exhibit both oxidizing and reducing properties. In addition, after the donation of an electron, it has 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, its main place is considered the first group of the main subgroup, where it is headed by the most active metals - alkali.
4. However, when interacting with strong reducing agents, such as, for example, metals, it can also be an oxidizing agent, accepting an electron. These compounds are called hydrides. On this basis, he heads the 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, which is why it is also the benchmark for lightness.

Thus, it is obvious that the hydrogen atom is completely unique, 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 it must be said 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 - through a single sigma-relationship H-H. The mechanism of bond formation between atoms is covalent non-polar.

1. Steam reforming of methane.
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 the melts do not lead to the discharge of water at the cathode.

Laboratory methods for producing hydrogen:

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

To collect the generated hydrogen, the tube must be held 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. Evaporates quickly, and explodes in large quantities when mixed with air. Therefore, the 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 lighted match to the neck. If the cotton is dull and quiet, then the gas is clean, with minimal air impurities. If it is loud and whistling, it is dirty, with a large proportion of extraneous components.

Areas of use

When hydrogen burns, so much 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 the 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 of obtaining this gas are quite expensive, therefore, first it is necessary to develop a special synthesis method. One that will allow you to get a product in large quantities and at minimal cost.

There are several main areas in which the gas we are considering finds application.

1. Chemical syntheses. Hydrogenation produces 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 an additive E949.
3. Aviation industry (rocketry, aircraft construction).
4. Electric power industry.
5. Meteorology.
6. Environmentally friendly fuel.

Obviously, hydrogen is just 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. There are several main types of such substances.

1. Hydrogen halides. The general formula is HHal. Among them, hydrogen chloride is of particular importance. It is a gas that dissolves in water to form a hydrochloric acid solution. This acid finds wide application 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 in terms of production in our country every year. 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. Moreover, it is very flammable.
3. Hydrides are compounds with metals. They 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, H 2 SO 4 and others.
5. Hydrogen hydroxide. This compound is better known as water. Another name for hydrogen oxide. The empirical formula looks like this - H 2 O.
6. Hydrogen peroxide. It is the strongest oxidizing agent, the formula of which is Н 2 О 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 great. This once again confirms its high importance for nature and man, as well as for all living beings.

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, which explains many of its properties. In particular, it is a universal solvent.

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

Water is considered to be 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 states of aggregation:

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

There are three types of water depending on the hydrogen isotope that is part of the molecule.

1. Lightweight or protium. An isotope with mass number 1. Formula - H 2 O. This is a common 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, the isotope is 3 N.

The reserves of fresh protium water on the planet are very important. Already now in many countries there is a lack of it. Methods are being developed for the treatment of salt water in order to obtain drinking water.

Hydrogen peroxide is a versatile remedy

This compound, as mentioned above, is an excellent oxidizing agent. However, with strong representatives it can behave as a restorer too. 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. A 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 has been proven that in this case, wound healing increases over time.

Hydrogen peroxide is also used in rocket fuel, in industry for disinfection and bleaching, as a foaming agent to obtain appropriate materials (foam, for example). In addition, peroxide helps clean aquariums, discolor hair, and whiten teeth. However, at the same time it damages the tissues, therefore, it is not recommended by specialists for these purposes.