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The hydrogen atom has the electronic formula of the outer (and only) electronic level 1 s one . On the one hand, by the presence of one electron in the outer electronic level, the hydrogen atom is similar to alkali metal atoms. However, just like halogens, it lacks only one electron to fill the external electronic level, since no more than 2 electrons can be located on the first electronic level. It turns out that hydrogen can be placed simultaneously in both the first and the penultimate (seventh) group of the periodic table, which is sometimes done in various versions of the periodic system:

From the point of view of the properties of hydrogen as a simple substance, it nevertheless has more in common with halogens. Hydrogen, as well as halogens, is a non-metal and forms diatomic molecules (H 2) similarly to them.

Under normal conditions, hydrogen is a gaseous, inactive substance. The low activity of hydrogen is explained by the high strength of the bond between hydrogen atoms in the molecule, which requires either strong heating or the use of catalysts, or both at the same time, to break it.

Interaction of hydrogen with simple substances

with metals

Of the metals, hydrogen reacts only with alkali and alkaline earth! Alkali metals include metals of the main subgroup of group I (Li, Na, K, Rb, Cs, Fr), and alkaline earth metals are metals of the main subgroup of group II, except for beryllium and magnesium (Ca, Sr, Ba, Ra)

When interacting with active metals, hydrogen exhibits oxidizing properties, i.e. lowers its oxidation state. In this case, hydrides of alkali and alkaline earth metals are formed, which have an ionic structure. The reaction proceeds when heated:

It should be noted that interaction with active metals is the only case when molecular hydrogen H2 is an oxidizing agent.

with non-metals

Of non-metals, hydrogen reacts only with carbon, nitrogen, oxygen, sulfur, selenium and halogens!

Carbon should be understood as graphite or amorphous carbon, since diamond is an extremely inert allotropic modification of carbon.

When interacting with non-metals, hydrogen can only perform the function of a reducing agent, that is, it can only increase its oxidation state:

Interaction of hydrogen with complex substances

with metal oxides

Hydrogen does not react with metal oxides that are in the activity series of metals up to aluminum (inclusive), however, it is able to reduce many metal oxides to the right of aluminum when heated:

with non-metal oxides

Of the non-metal oxides, hydrogen reacts when heated with oxides of nitrogen, halogens, and carbon. Of all the interactions of hydrogen with non-metal oxides, its reaction with carbon monoxide CO should be especially noted.

The mixture of CO and H 2 even has its own name - “synthesis gas”, since, depending on the conditions, such demanded industrial products as methanol, formaldehyde and even synthetic hydrocarbons can be obtained from it:

with acids

Hydrogen does not react with inorganic acids!

Of the organic acids, hydrogen reacts only with unsaturated acids, as well as with acids containing functional groups capable of being reduced by hydrogen, in particular aldehyde, keto or nitro groups.

with salts

In the case of aqueous solutions of salts, their interaction with hydrogen does not occur. However, when hydrogen is passed over solid salts of some metals of medium and low activity, their partial or complete reduction is possible, for example:

Chemical properties of halogens

Halogens are the chemical elements of group VIIA (F, Cl, Br, I, At), as well as the simple substances they form. Hereinafter, unless otherwise stated, halogens will be understood as simple substances.

All halogens have a molecular structure, which leads to low melting and boiling points of these substances. Halogen molecules are diatomic, i.e. their formula can be written in general form as Hal 2 .

It should be noted such a specific physical property of iodine as its ability to sublimation or, in other words, sublimation. sublimation, they call the phenomenon in which a substance in the solid state does not melt when heated, but, bypassing the liquid phase, immediately passes into the gaseous state.

The electronic structure of the external energy level of an atom of any halogen has the form ns 2 np 5, where n is the period number of the periodic table in which the halogen is located. As you can see, only one electron is missing from the eight-electron outer shell of the halogen atoms. From this it is logical to assume the predominantly oxidizing properties of free halogens, which is also confirmed in practice. As you know, the electronegativity of non-metals decreases when moving down the subgroup, and therefore the activity of halogens decreases in the series:

F 2 > Cl 2 > Br 2 > I 2

Interaction of halogens with simple substances

All halogens are highly reactive and react with most simple substances. However, it should be noted that fluorine, due to its extremely high reactivity, can react even with those simple substances with which other halogens cannot react. Such simple substances include oxygen, carbon (diamond), nitrogen, platinum, gold, and some noble gases (xenon and krypton). Those. actually, fluorine does not react only with some noble gases.

The remaining halogens, i.e. chlorine, bromine and iodine are also active substances, but less active than fluorine. They react with almost all simple substances except oxygen, nitrogen, carbon in the form of diamond, platinum, gold and noble gases.

Interaction of halogens with non-metals

hydrogen

All halogens react with hydrogen to form hydrogen halides with the general formula HHal. At the same time, the reaction of fluorine with hydrogen begins spontaneously even in the dark and proceeds with an explosion in accordance with the equation:

The reaction of chlorine with hydrogen can be initiated by intense ultraviolet irradiation or heating. Also leaks with an explosion:

Bromine and iodine react with hydrogen only when heated, and at the same time, the reaction with iodine is reversible:

phosphorus

The interaction of fluorine with phosphorus leads to the oxidation of phosphorus to the highest oxidation state (+5). In this case, the formation of phosphorus pentafluoride occurs:

When chlorine and bromine interact with phosphorus, it is possible to obtain phosphorus halides both in the + 3 oxidation state and in the + 5 oxidation state, which depends on the proportions of the reactants:

In the case of white phosphorus in an atmosphere of fluorine, chlorine or liquid bromine, the reaction begins spontaneously.

The interaction of phosphorus with iodine can lead to the formation of only phosphorus triiodide due to the significantly lower oxidizing ability than other halogens:

gray

Fluorine oxidizes sulfur to the highest oxidation state +6, forming sulfur hexafluoride:

Chlorine and bromine react with sulfur, forming compounds containing sulfur in oxidation states that are extremely unusual for it +1 and +2. These interactions are very specific, and to pass the exam in chemistry, the ability to write down the equations of these interactions is not necessary. Therefore, the following three equations are given rather for guidance:

Interaction of halogens with metals

As mentioned above, fluorine is able to react with all metals, even such inactive ones as platinum and gold:

The remaining halogens react with all metals except platinum and gold:

Reactions of halogens with complex substances

Substitution reactions with halogens

More active halogens, i.e. the chemical elements of which are located higher in the periodic table, are able to displace less active halogens from the hydrohalic acids and metal halides they form:

Similarly, bromine and iodine displace sulfur from solutions of sulfides and or hydrogen sulfide:

Chlorine is a stronger oxidizing agent and oxidizes hydrogen sulfide in its aqueous solution not to sulfur, but to sulfuric acid:

Interaction of halogens with water

Water burns in fluorine with a blue flame in accordance with the reaction equation:

Bromine and chlorine react differently with water than fluorine. If fluorine acted as an oxidizing agent, then chlorine and bromine disproportionate in water, forming a mixture of acids. In this case, the reactions are reversible:

The interaction of iodine with water proceeds to such an insignificant degree that it can be neglected and considered that the reaction does not proceed at all.

Interaction of halogens with alkali solutions

Fluorine, when interacting with an aqueous solution of alkali, again acts as an oxidizing agent:

The ability to write this equation is not required to pass the exam. It is enough to know the fact about the possibility of such an interaction and the oxidizing role of fluorine in this reaction.

Unlike fluorine, the remaining halogens disproportionate in alkali solutions, that is, they simultaneously increase and decrease their oxidation state. At the same time, in the case of chlorine and bromine, depending on the temperature, flow in two different directions is possible. In particular, in the cold, the reactions proceed as follows:

and when heated:

Iodine reacts with alkalis exclusively according to the second option, i.e. with the formation of iodate, because hypoiodite is unstable not only when heated, but also at ordinary temperatures and even in the cold.

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

Brief information about opening an element

Before considering 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 combustible 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 at that time were not studied. Only at the end of the eighteenth century, A. Lavoisier managed to establish by analysis that this gas can be obtained by analyzing water. A little later, he began to call the new element hydrogene, which 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 abundance 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 an integral part of water.

In addition, this non-metal is found in animal organisms in the form of nucleic acids, proteins, carbohydrates, and 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 about 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, 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 a gaseous substance lighter than air, having several isotopic forms. It is almost insoluble in water and has a 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, the reactions characteristic of it, let us dwell on the features of its structure. This diatomic molecule has a covalent non-polar chemical bond. The formation of atomic hydrogen is possible when active metals interact with acid solutions. But in this form, this non-metal is able to exist only for an insignificant time period, almost immediately it recombines into a molecular form.

Chemical properties

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, characterizing it as a metal:

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

Below is the reaction equation that characterizes the chemical properties of hydrogen. We draw attention to the fact that as a non-metal (with an oxidation state of -1), it acts only in the reaction with active metals, forming the corresponding hydrides with them.

Hydrogen at ordinary temperature does not actively interact with other substances, so most of the reactions are carried out only after preheating.

Let us dwell in more detail on some chemical interactions of the element that heads the periodic system of chemical elements of 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 gaseous hydrogen that have found significant application in industry, its interaction with metal oxides is of interest. It is by catalytic hydrogenation in modern industry that metal oxides are processed, for example, pure metal is isolated from iron scale (mixed iron oxide). This method allows for efficient processing of scrap metal.

The synthesis of ammonia, which involves the interaction of hydrogen with atmospheric nitrogen, is also in demand in the modern chemical industry. Among the conditions for the occurrence of this chemical interaction, we note pressure and temperature.

Conclusion

It is hydrogen that is an inactive 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 to primary alcohols. In addition, by hydrogenation, unsaturated hydrocarbons of the ethylene and acetylene classes can be converted into saturated compounds of the methane series. Hydrogen is rightly considered a simple substance in demand in modern chemical production.

The most abundant element in the universe is hydrogen. In the matter of stars, it has the form of nuclei - protons - and is the material for thermonuclear processes. Almost half of the mass of the Sun also consists of H 2 molecules. Its content in the earth's crust reaches 0.15%, and atoms are present in the composition of oil, natural gas, and water. Together with oxygen, nitrogen and carbon, it is an organogenic element that is part of all living organisms on Earth. In our article, we will study the physical and chemical properties of hydrogen, determine the main areas of its application in industry and its significance in nature.

Position in the periodic system of chemical elements of Mendeleev

The first element to open the periodic table is hydrogen. Its atomic mass is 1.0079. It has two stable (protium and deuterium) and one radioactive isotope (tritium). Physical properties are determined by the place of the non-metal in the table of chemical elements. Under normal conditions, hydrogen (its formula is H 2) is a gas that is almost 15 times lighter than air. The structure of an element's atom is unique: it consists of only a nucleus and one electron. The molecule of a substance is diatomic, the particles in it are connected using a covalent non-polar bond. Its energy intensity is quite high - 431 kJ. This explains the low chemical activity of the compound under normal conditions. The electronic formula of hydrogen is: H:H.

The substance also has a number of properties that have no analogues among other non-metals. Let's consider some of them.

Solubility and thermal conductivity

Metals conduct heat best, but hydrogen approaches them in terms of thermal conductivity. The explanation of the phenomenon lies in the very high speed of the thermal movement of light molecules of matter, therefore, in a hydrogen atmosphere, a heated object cools down 6 times faster than in air. The compound can dissolve well in metals, for example, almost 900 volumes of hydrogen can be absorbed by one volume of palladium. Metals can enter into chemical reactions with H 2 in which the oxidizing properties of hydrogen are manifested. In this case, hydrides are formed:

2Na + H 2 \u003d 2 NaH.

In this reaction, the atoms of an element accept electrons from metal particles, turning into anions with a unit negative charge. A simple substance H 2 in this case is an oxidizing agent, which is usually not typical for it.

Hydrogen as a reducing agent

Metals and hydrogen are united not only by high thermal conductivity, but also by the ability of their atoms in chemical processes to donate their own electrons, that is, to be oxidized. For example, basic oxides react with hydrogen. The redox reaction ends with the release of pure metal and the formation of water molecules:

CuO + H 2 \u003d Cu + H 2 O.

The interaction of a substance with oxygen during heating also leads to the production of water molecules. The process is exothermic and is accompanied by the release of a large amount of thermal energy. If a gas mixture of H 2 and O 2 reacts in a ratio of 2: 1, then it is called because it explodes when ignited:

2H 2 + O 2 \u003d 2H 2 O.

Water is and plays an important role in the formation of the Earth's hydrosphere, climate, and weather. It provides the circulation of elements in nature, supports all the life processes of organisms - the inhabitants of our planet.

Interaction with non-metals

The most important chemical properties of hydrogen are its reactions with non-metallic elements. Under normal conditions, they are quite chemically inert, so the substance can only react with halogens, for example, with fluorine or chlorine, which are the most active among all non-metals. So, a mixture of fluorine and hydrogen explodes in the dark or in the cold, and with chlorine - when heated or in the light. The reaction products will be hydrogen halides, the aqueous solutions of which are known as fluoride and chloride acids. C interacts at a temperature of 450-500 degrees, a pressure of 30-100 MPa and in the presence of a catalyst:

N₂ + 3H₂ ⇔ p, t, kat ⇔ 2NH₃.

The considered chemical properties of hydrogen are of great importance for industry. For example, you can get a valuable chemical product - ammonia. It is the main raw material for the production of nitrate acid and nitrogen fertilizers: urea, ammonium nitrate.

organic matter

Between carbon and hydrogen leads to the production of the simplest hydrocarbon - methane:

C + 2H 2 = CH 4.

The substance is the most important component of the natural substance and is used as a valuable type of fuel and raw material for the industry of organic synthesis.

In the chemistry of carbon compounds, an element is included in a huge number of substances: alkanes, alkenes, carbohydrates, alcohols, etc. Many reactions of organic compounds with H 2 molecules are known. They are collectively known as hydrogenation or hydrogenation. So, aldehydes can be reduced with hydrogen to alcohols, unsaturated hydrocarbons - to alkanes. For example, ethylene is converted to ethane:

C 2 H 4 + H 2 \u003d C 2 H 6.

Of great practical importance are such chemical properties of hydrogen as, for example, the hydrogenation of liquid oils: sunflower, corn, and rapeseed. It leads to the production of solid fat - lard, which is used in the production of glycerin, soap, stearin, hard margarine. To improve the appearance and taste of a food product, milk, animal fats, sugar, and vitamins are added to it.

In our article, we studied the properties of hydrogen and found out its role in nature and human life.

DEFINITION

Hydrogen- the first element of the Periodic system of chemical elements of D.I. Mendeleev. The symbol is N.

Atomic mass - 1 a.m.u. The hydrogen molecule is diatomic - H 2.

The electronic configuration of the hydrogen atom is 1s 1. Hydrogen belongs to the s-element family. In its compounds, it exhibits oxidation states -1, 0, +1. Natural hydrogen consists of two stable isotopes - protium 1 H (99.98%) and deuterium 2 H (D) (0.015%) - and a radioactive isotope of tritium 3 H (T) (trace amounts, half-life - 12.5 years) .

Chemical properties of hydrogen

Under normal conditions, molecular hydrogen exhibits a relatively low reactivity, which is explained by the high bond strength in the molecule. When heated, it interacts with almost all simple substances formed by elements of the main subgroups (except for noble gases, B, Si, P, Al). In chemical reactions, it can act both as a reducing agent (more often) and an oxidizing agent (less often).

Hydrogen manifests reducing agent properties(H 2 0 -2e → 2H +) in the following reactions:

1. Reactions of interaction with simple substances - non-metals. Hydrogen reacts with halogens, moreover, the reaction of interaction with fluorine under normal conditions, in the dark, with an explosion, with chlorine - under illumination (or UV irradiation) by a chain mechanism, with bromine and iodine only when heated; oxygen(a mixture of oxygen and hydrogen in a 2:1 volume ratio is called "explosive gas"), gray, nitrogen and carbon:

H 2 + Hal 2 \u003d 2HHal;

2H 2 + O 2 \u003d 2H 2 O + Q (t);

H 2 + S \u003d H 2 S (t \u003d 150 - 300C);

3H 2 + N 2 ↔ 2NH 3 (t = 500C, p, kat = Fe, Pt);

2H 2 + C ↔ CH 4 (t, p, kat).

2. Reactions of interaction with complex substances. Hydrogen reacts with oxides of low-active metals, and it is able to reduce only metals that are in the activity series to the right of zinc:

CuO + H 2 \u003d Cu + H 2 O (t);

Fe 2 O 3 + 3H 2 \u003d 2Fe + 3H 2 O (t);

WO 3 + 3H 2 \u003d W + 3H 2 O (t).

Hydrogen reacts with non-metal oxides:

H 2 + CO 2 ↔ CO + H 2 O (t);

2H 2 + CO ↔ CH 3 OH (t = 300C, p = 250 - 300 atm., kat = ZnO, Cr 2 O 3).

Hydrogen enters into hydrogenation reactions with organic compounds of the class of cycloalkanes, alkenes, arenes, aldehydes and ketones, etc. All these reactions are carried out under heating, under pressure, platinum or nickel is used as catalysts:

CH 2 \u003d CH 2 + H 2 ↔ CH 3 -CH 3;

C 6 H 6 + 3H 2 ↔ C 6 H 12;

C 3 H 6 + H 2 ↔ C 3 H 8;

CH 3 CHO + H 2 ↔ CH 3 -CH 2 -OH;

CH 3 -CO-CH 3 + H 2 ↔ CH 3 -CH (OH) -CH 3.

Hydrogen as an oxidizing agent(H 2 + 2e → 2H -) acts in reactions with alkali and alkaline earth metals. In this case, hydrides are formed - crystalline ionic compounds in which hydrogen exhibits an oxidation state of -1.

2Na + H 2 ↔ 2NaH (t, p).

Ca + H 2 ↔ CaH 2 (t, p).

Physical properties of hydrogen

Hydrogen is a light colorless gas, odorless, density at n.o. - 0.09 g / l, 14.5 times lighter than air, t bale = -252.8C, t pl = - 259.2C. Hydrogen is poorly soluble in water and organic solvents, it is highly soluble in some metals: nickel, palladium, platinum.

According to modern cosmochemistry, hydrogen is the most abundant element in the universe. The main form of existence of hydrogen in outer space is individual atoms. Hydrogen is the 9th most abundant element on Earth. The main amount of hydrogen on Earth is in a bound state - in the composition of water, oil, natural gas, coal, etc. In the form of a simple substance, hydrogen is rarely found - in the composition of volcanic gases.

Getting hydrogen

There are laboratory and industrial methods for producing hydrogen. Laboratory methods include the interaction of metals with acids (1), as well as the interaction of aluminum with aqueous solutions of alkalis (2). Among the industrial methods for producing hydrogen, the electrolysis of aqueous solutions of alkalis and salts (3) and the conversion of methane (4) play an important role:

Zn + 2HCl = ZnCl 2 + H 2 (1);

2Al + 2NaOH + 6H 2 O = 2Na +3 H 2 (2);

2NaCl + 2H 2 O = H 2 + Cl 2 + 2NaOH (3);

CH 4 + H 2 O ↔ CO + H 2 (4).

Examples of problem solving

EXAMPLE 1

EXAMPLE 2

Starting to consider the chemical and physical properties of hydrogen, it should be noted that in the usual state, this chemical element is in gaseous form. Colorless hydrogen gas is odorless and tasteless. For the first time, this chemical element was named hydrogen after the scientist A. Lavoisier conducted experiments with water, according to the results of which, world science learned that water is a multicomponent liquid, which includes Hydrogen. This event occurred in 1787, but long before that date, hydrogen was known to scientists under the name "combustible gas".

Hydrogen in nature

According to scientists, hydrogen is found in the earth's crust and in water (approximately 11.2% of the total volume of water). This gas is part of many minerals that mankind has been extracting from the bowels of the earth for centuries. In part, the properties of hydrogen are characteristic of oil, natural gases and clay, for animal and plant organisms. But in its pure form, that is, not combined with other chemical elements of the periodic table, this gas is extremely rare in nature. This gas can escape to the earth's surface during volcanic eruptions. Free hydrogen is present in trace amounts in the atmosphere.

Chemical properties of hydrogen

Since the chemical properties of hydrogen are not uniform, this chemical element belongs both to group I of the Mendeleev system and to group VII of the system. Being a representative of the first group, hydrogen is, in fact, an alkali metal that has an oxidation state of +1 in most of the compounds in which it is included. The same valence is characteristic of sodium and other alkali metals. In view of these chemical properties, hydrogen is considered to be an element similar to these metals.

If we are talking about metal hydrides, then the hydrogen ion has a negative valence - its oxidation state is -1. Na + H- is built in the same way as Na + Cl- chloride. This fact is the reason for assigning hydrogen to group VII of the Mendeleev system. Hydrogen, being in the state of a molecule, provided that it is in an ordinary environment, is inactive, and can only combine with non-metals that are more active for it. Such metals include fluorine, in the presence of light, hydrogen combines with chlorine. If hydrogen is heated, it becomes more active, reacting with many elements of the periodic system of Mendeleev.

Atomic hydrogen exhibits more active chemical properties than molecular hydrogen. Oxygen molecules form water - H2 + 1/2O2 = H2O. When hydrogen interacts with halogens, hydrogen halides H2 + Cl2 = 2HCl are formed, and hydrogen enters into this reaction in the absence of light and at sufficiently high negative temperatures - up to - 252 ° C. The chemical properties of hydrogen make it possible to use it for the reduction of many metals, since, when reacting, hydrogen absorbs oxygen from metal oxides, for example, CuO + H2 = Cu + H2O. Hydrogen is involved in the formation of ammonia, interacting with nitrogen in the reaction 3H2 + N2 = 2NH3, but on the condition that a catalyst is used, and the temperature and pressure are increased.

An energetic reaction occurs when hydrogen interacts with sulfur in the reaction H2 + S = H2S, which results in hydrogen sulfide. The interaction of hydrogen with tellurium and selenium is slightly less active. If there is no catalyst, then it reacts with pure carbon, hydrogen only under the condition that high temperatures are created. 2H2 + C (amorphous) = CH4 (methane). In the process of hydrogen activity with some alkali and other metals, hydrides are obtained, for example, H2 + 2Li = 2LiH.

Physical properties of hydrogen

Hydrogen is a very light chemical. At the very least, scientists claim that at the moment, there is no lighter substance than hydrogen. Its mass is 14.4 times lighter than air, its density is 0.0899 g/l at 0°C. At temperatures of -259.1 ° C, hydrogen is capable of melting - this is a very critical temperature, which is not typical for the transformation of most chemical compounds from one state to another. Only such an element as helium exceeds the physical properties of hydrogen in this regard. The liquefaction of hydrogen is difficult, since its critical temperature is (-240°C). Hydrogen is the most heat-producing gas of all known to mankind. All the properties described above are the most significant physical properties of hydrogen that are used by man for specific purposes. Also, these properties are the most relevant for modern science.

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