Atomic number of hydrogen. Hydrogen - characteristics, physical and chemical properties

The hydrogen atom has the electronic formula of the outer (and only) electron level 1 s 1 . On the one hand, in terms of the presence of one electron on the outer electronic level, the hydrogen atom is similar to alkali metal atoms. However, just like halogens, it only needs one electron to fill the outer electronic level, since the first electronic level can contain no more than 2 electrons. 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 table:

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

Under normal conditions, hydrogen is a gaseous, low-active substance. The low activity of hydrogen is explained by the high strength of the bonds between the hydrogen atoms in the molecule, the breaking of which requires either strong heating, or the use of catalysts, or both.

Interaction of hydrogen with simple substances

with metals

Of the metals, hydrogen reacts only with alkali and alkaline earth metals! Alkali metals include metals of the main subgroup of group I (Li, Na, K, Rb, Cs, Fr), and alkaline earth metals include metals of the main subgroup of group II, except 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 occurs 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 the 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, 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 capable of reducing many metal oxides to the right of aluminum when heated:

with non-metal oxides

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

The mixture of CO and H2 even has its own name - “synthesis gas”, since, depending on the conditions, such popular industrial products as methanol, formaldehyde and even synthetic hydrocarbons can be obtained from it:

with acids

Hydrogen does not react with inorganic acids!

Of organic acids, hydrogen reacts only with unsaturated acids, as well as with acids containing functional groups capable of reduction with 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. Here and further in the text, unless otherwise stated, halogens will be understood as simple substances.

All halogens have a molecular structure, which determines the 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, is a phenomenon in which a substance in a 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 number of the periodic table period in which the halogen is located. As you can see, the halogen atoms only need one electron to reach the eight-electron outer shell. From this it is logical to assume the predominantly oxidizing properties of free halogens, which is confirmed in practice. As is known, the electronegativity of nonmetals decreases when moving down a 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 substances 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

When all halogens interact with hydrogen, they form hydrogen halides with the general formula HHal. In this case, 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 heat. Also proceeds with 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, phosphorus pentafluoride is formed:

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

Moreover, 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 triodide due to its significantly lower oxidizing ability than that of 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 the oxidation states +1 and +2, which are extremely unusual for it. These interactions are very specific, and to pass the Unified State Exam in chemistry, the ability to write equations for these interactions is not necessary. Therefore, the following three equations are given rather for reference:

Interaction of halogens with metals

As mentioned above, fluorine is capable of reacting 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 capable of displacing 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:

Reaction 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 are disproportionate in water, forming a mixture of acids. In this case, the reactions are reversible:

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

Interaction of halogens with alkali solutions

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

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

Unlike fluorine, other halogens in alkali solutions are disproportionate, that is, they simultaneously increase and decrease their oxidation state. Moreover, 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 not stable not only when heated, but also at ordinary temperatures and even in the cold.

The most common element in the universe is hydrogen. In the matter of stars, it has the form of nuclei - protons - and is a material for thermonuclear processes. Almost half of the Sun's mass also consists of H 2 molecules. Its content in the earth's crust reaches 0.15%, and atoms are present in 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 Mendeleev's periodic table of chemical elements

The first element to discover the periodic table is hydrogen. Its atomic mass is 1.0079. It has two stable isotopes (protium and deuterium) and one radioactive isotope (tritium). Physical properties are determined by the place of the nonmetal in the table of chemical elements. Under normal conditions, hydrogen (its formula is H2) is a gas that is almost 15 times lighter than air. The structure of the element's atom is unique: it consists of only a nucleus and one electron. The molecule of the substance is diatomic; the particles in it are connected using a covalent nonpolar 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 look at some of them.

Solubility and thermal conductivity

Metals conduct heat best, but hydrogen is close to them in thermal conductivity. The explanation for the phenomenon lies in the very high speed of thermal movement of light molecules of a substance, therefore in a hydrogen atmosphere a heated object cools down 6 times faster than in air. The compound can be highly soluble in metals; for example, almost 900 volumes of hydrogen can be absorbed by one volume of palladium. Metals can enter into chemical reactions with H2, in which the oxidizing properties of hydrogen are manifested. In this case, hydrides are formed:

2Na + H 2 =2 NaH.

In this reaction, atoms of the element accept electrons from metal particles, becoming anions with a single negative charge. The simple substance H2 in this case is an oxidizing agent, which is usually not typical for it.

Hydrogen as a reducing agent

What unites metals and hydrogen is not only high thermal conductivity, but also the ability of their atoms in chemical processes to give up their own electrons, that is, to oxidize. 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 = Cu + H 2 O.

The interaction of a substance with oxygen when heated also leads to the formation 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 2:1 ratio, then it is called because it explodes when ignited:

2H 2 + O 2 = 2H 2 O.

Water is and plays a vital role in the formation of the Earth’s hydrosphere, climate, and weather. It ensures 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. Thus, 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, 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 obtain 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 natural and They are used as a valuable type of fuel and raw material for the organic synthesis industry.

In the chemistry of carbon compounds, the element is part of a huge number of substances: alkanes, alkenes, carbohydrates, alcohols, etc. Many reactions of organic compounds with H 2 molecules are known. They have a common name - hydrogenation or hydrogenation. Thus, 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 = C 2 H 6.

The chemical properties of hydrogen, such as, for example, the hydrogenation of liquid oils: sunflower, corn, rapeseed, are of important practical importance. It leads to the production of solid fat - lard, which is used in the production of glycerin, soap, stearin, and 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.

When starting to consider the chemical and physical properties of hydrogen, it should be noted that in its 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, as a result of which world science learned that water is a multicomponent liquid that contains Hydrogen. This event occurred in 1787, but long before this date, hydrogen was known to scientists under the name “flammable gas.”

Hydrogen in nature

According to scientists, hydrogen is contained 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 humanity has been extracting from the bowels of the earth for centuries. Some of the properties of hydrogen are characteristic of oil, natural gases and clay, and of 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 come to the surface of the earth during volcanic eruptions. Free hydrogen is present in the atmosphere in negligible quantities.

Chemical properties of hydrogen

Since the chemical properties of hydrogen are heterogeneous, this chemical element belongs to both group I of the Mendeleev system and group VII of the system. As a member of the first group, hydrogen is essentially an alkali metal that has an oxidation state of +1 in most of the compounds in which it is found. The same valency is characteristic of sodium and other alkali metals. Due to these chemical properties, hydrogen is considered an element similar to these metals.

If we are talking about metal hydrides, then the hydrogen ion has a negative valency - its oxidation state is -1. Na+H- is built according to the same scheme as Na+Cl- chloride. This fact is the reason to assign hydrogen to group VII of the periodic system. Hydrogen, being in the state of a molecule, provided that it is in an ordinary environment, is inactive, and can combine exclusively with non-metals that are more active for it. These 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 table 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 fairly 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 it reacts, hydrogen absorbs oxygen from metal oxides, for example, CuO + H2 = Cu + H2O. Hydrogen participates in the formation of ammonia by interacting with nitrogen in the reaction ZH2 + N2 = 2NH3, but provided that a catalyst is used and the temperature and pressure are increased.

A vigorous reaction occurs when hydrogen reacts 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). During the activity of hydrogen 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 least, scientists say 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 an element such 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-conducting gas known to mankind. All the properties described above are the most significant physical properties of hydrogen that are used by humans for specific purposes. Also, these properties are the most relevant for modern science.

Hydrogen is the very first element in the Periodic Table of Chemical Elements and has an atomic number of 1 and a relative atomic mass of 1.0079. What are the physical properties of hydrogen?

Physical properties of hydrogen

Translated from Latin, hydrogen means “giving birth to water.” Back in 1766, the English scientist G. Cavendish collected “combustible air” released when acids act on metals and began to study its properties. In 1787, A. Lavoisier identified this “combustible air” as a new chemical element that is part of water.

Rice. 1. A. Lavoisier.

Hydrogen has 2 stable isotopes - protium and deuterium, as well as a radioactive one - tritium, the amount of which is very small on our planet.

Hydrogen is the most abundant element in space. The Sun and most stars have hydrogen as their main element. This gas is also found in water, oil, and natural gas. The total hydrogen content on Earth is 1%.

Rice. 2. Formula of hydrogen.

An atom of this substance contains a nucleus and one electron. When hydrogen loses an electron, it forms a positively charged ion, which means it exhibits metallic properties. But the hydrogen atom is also capable of not only losing, but also gaining an electron. In this it is very similar to halogens. Therefore, hydrogen in the Periodic Table belongs to both groups I and VII. The non-metallic properties of hydrogen are more pronounced.

A hydrogen molecule consists of two atoms connected by a covalent bond

Under normal conditions, hydrogen is a colorless gaseous element that is odorless and tasteless. It is 14 times lighter than air, and its boiling point is -252.8 degrees Celsius.

Table “Physical properties of hydrogen”

In addition to physical properties, hydrogen also has a number of chemical properties. Hydrogen, when heated or under the influence of catalysts, reacts with metals and non-metals, sulfur, selenium, tellurium, and can also reduce the oxides of many metals.

Hydrogen production

Of the industrial methods for producing hydrogen (except for electrolysis of aqueous salt solutions), the following should be noted:

• passing water vapor through hot coal at a temperature of 1000 degrees:

• methane conversion with water vapor at a temperature of 900 degrees:

CH 4 +2H 2 O=CO 2 +4H 2

Rice. 3. Steam methane reforming.

• decomposition of methane in the presence of a catalyst (Ni) at a temperature of 400 degrees:

Hydrogen is number one in the periodic table, in groups I and VII at once. The symbol for hydrogen is H (lat. Hydrogenium). It is a very light gas, colorless and odorless. There are three isotopes of hydrogen: 1H - protium, 2H - deuterium and 3H - tritium (radioactive). Air or oxygen in reaction with simple hydrogen H₂ is highly flammable and also explosive. Hydrogen does not emit toxic products. It is soluble in ethanol and a number of metals (especially the side subgroup).

Hydrogen abundance on Earth

Like oxygen, hydrogen is of great importance. But, unlike oxygen, almost all hydrogen is bound to other substances. It is found in a free state only in the atmosphere, but its quantity there is extremely insignificant. Hydrogen is part of almost all organic compounds and living organisms. Most often it is found in the form of an oxide - water.

Physicochemical characteristics

Hydrogen is inactive, and when heated or in the presence of catalysts, it reacts with almost all simple and complex chemical elements.

Reaction of hydrogen with simple chemical elements

At elevated temperatures, hydrogen reacts with oxygen, sulfur, chlorine and nitrogen. you will learn what experiments with gases can be done at home.

Experience of interaction of hydrogen with oxygen in laboratory conditions

Let's take pure hydrogen, which comes through the gas outlet tube, and set it on fire. It will burn with a barely noticeable flame. If you place a hydrogen tube in any vessel, it will continue to burn, and water droplets will form on the walls. This oxygen reacted with hydrogen:

2Н₂ + О₂ = 2Н₂О + Q

When hydrogen burns, a lot of thermal energy is generated. The temperature of the combination of oxygen and hydrogen reaches 2000 °C. Oxygen oxidized hydrogen, so this reaction is called an oxidation reaction.

Under normal conditions (without heating), the reaction proceeds slowly. And at temperatures above 550 ° C an explosion occurs (the so-called detonating gas is formed). In the past, hydrogen was often used in balloons, but there were many accidents due to the formation of the detonating gas. The integrity of the ball was violated, and an explosion occurred: hydrogen reacted with oxygen. Therefore, helium is now used, which is periodically heated with a flame.

Chlorine reacts with hydrogen to form hydrogen chloride (only in the presence of light and heat). The chemical reaction of hydrogen and chlorine looks like this:

H₂ + Cl₂ = 2HCl

Interesting fact: the reaction of fluorine with hydrogen causes an explosion even in darkness and temperatures below 0 ° C.

The interaction of nitrogen with hydrogen can only occur when heated and in the presence of a catalyst. This reaction produces ammonia. Reaction equation:

ЗН₂ + N₂ = 2NN₃

The reaction of sulfur and hydrogen occurs to form a gas - hydrogen sulfide. The result is a rotten egg smell:

H₂ + S = H₂S

Hydrogen not only dissolves in metals, but can also react with them. As a result, compounds are formed that are called hydrides. Some hydrides are used as fuel in rockets. They are also used to produce nuclear energy.

Reaction with complex chemical elements

For example, hydrogen with copper oxide. Let's take a tube of hydrogen and pass it through the copper oxide powder. The entire reaction occurs when heated. Black copper powder will turn brownish red (plain copper color). Droplets of liquid will also appear on the unheated areas of the flask - this has formed.

Chemical reaction:

CuO + H₂ = Cu + H₂O

As we can see, hydrogen reacted with the oxide and reduced copper.

Recovery reactions

If a substance removes an oxide during a reaction, it is a reducing agent. Using the example of the reaction of copper oxide with we see that hydrogen was a reducing agent. It also reacts with some other oxides such as HgO, MoO₃ and PbO. In any reaction, if one of the elements is an oxidizing agent, the other will be a reducing agent.

All hydrogen compounds

Hydrogen compounds with nonmetals- very volatile and poisonous gases (for example, hydrogen sulfide, silane, methane).

Hydrogen halides- Hydrogen chloride is most commonly used. When dissolved, it forms hydrochloric acid. This group also includes: hydrogen fluoride, hydrogen iodide and hydrogen bromide. All these compounds result in the formation of the corresponding acids.

Hydrogen peroxide(chemical formula H₂O₂) exhibits strong oxidizing properties.

Hydrogen hydroxides or water H₂O.

Hydrides- these are compounds with metals.

Hydroxides- these are acids, bases and other compounds that contain hydrogen.

Organic compounds: proteins, fats, lipids, hormones and others.