Hydrogen H is a chemical element, one of the most common in our universe. The mass of hydrogen as an element in the composition of substances is 75% of the total content of atoms of another type. It enters the most important and vital connection on the planet - water. A distinctive feature of hydrogen is also that it is the first element in the periodic system of chemical elements of D. I. Mendeleev.
Discovery and research
The first mention of hydrogen in the works of Paracelsus dates from the sixteenth century. But its separation from the gas mixture of air and the study of combustible properties were already made in the seventeenth century by the scientist Lemery. The English chemist, physicist and natural scientist Henry Cavendish thoroughly studied hydrogen , who experimentally proved that the mass of hydrogen is the smallest in comparison with other gases. In the subsequent stages of the development of science, many scientists worked with him, in particular Lavoisier, who called him "giving birth to water."
Characteristic of the situation in the PSCE
The element that opens the periodic table of D. I. Mendeleev is hydrogen. The physical and chemical properties of the atom exhibit a certain duality, since the hydrogen is simultaneously assigned to the first group, the main subgroup, if it behaves like a metal and gives off a single electron in the course of a chemical reaction, and to the seventh in the case of a complete filling of the valence shell, i.e. negative particle, which characterizes it as similar to halogens.
Features of the electronic structure of the element
The properties of the hydrogen atom, the complex substances it contains, and the simplest substance H 2 are primarily determined by the electronic configuration of the hydrogen. A particle has one electron with Z = (-1), which rotates in its orbit around a nucleus containing one proton with a unit mass and a positive charge (+1). Its electronic configuration is written as 1s 1 , which means the presence of one negative particle on the very first and only s-orbital for hydrogen.
When an electron is detached or recoiled, and the atom of this element has such a property that it makes it related to metals, a cation is obtained. In fact, a hydrogen ion is a positive elementary particle. Therefore, an electron-free hydrogen is simply called a proton.
Physical properties
Briefly describing the physical properties of hydrogen, it is a colorless, sparingly soluble gas with a relative atomic mass of 2, 14.5 times lighter than air, with a liquefaction temperature of -252.8 degrees Celsius.
From experience, one can easily verify that H 2 is the lightest. To do this, it is enough to fill three balls with various substances - hydrogen, carbon dioxide, ordinary air - and at the same time release them from your hand. The fastest to reach the earth is one that is filled with CO 2 , after it the inflated air mixture will drop, and the one containing H 2 will rise to the ceiling altogether.
The small mass and particle size of hydrogen justify its ability to penetrate various substances. Using the example of the same ball, it is easy to verify this, in a couple of days it will deflate itself, since the gas will simply pass through the rubber. Also, hydrogen can accumulate in the structure of some metals (palladium or platinum), and evaporate from it with increasing temperature.
The low solubility property of hydrogen is used in laboratory practice to isolate it by water displacement . The physical properties of hydrogen (the table below contains the main parameters) determine the scope of its application and methods of production.
| The parameter of an atom or molecule of a simple substance | Value |
| Atomic mass (molar mass) | 1.008 g / mol |
| Electronic configuration | 1s 1 |
| Crystal cell | Hexagonal |
| Thermal conductivity | (300 K) 0.1815 W / (mK) |
| Density at n at. | 0.08987 g / l |
| Boiling temperature | -252.76 ยฐ C |
| Specific heat of combustion | 120.9 ยท 10 6 J / kg |
| Melting temperature | -259.2 ยฐ C |
| Solubility in water | 18.8 ml / l |
Isotopic composition
Like many other representatives of the periodic system of chemical elements, the hydrogen has several natural isotopes, that is, atoms with the same number of protons in the nucleus, but with a different number of neutrons - particles with zero charge and unit mass. Examples of atoms with a similar property are oxygen, carbon, chlorine, bromine, and others, including radioactive ones.
The physical properties of hydrogen 1 H, the most common of the representatives of this group, differ significantly from the same characteristics of its counterparts. In particular, the characteristics of the substances in which they are included vary. So, there is ordinary and deuterated water, containing instead of a hydrogen atom with a single proton, deuterium 2 N - its isotope with two elementary particles: positive and uncharged. This isotope is two times heavier than ordinary hydrogen, which explains the fundamental difference in the properties of the compounds that they make up. In nature, deuterium is found 3200 times less than hydrogen. The third representative is tritium 3 N; in the nucleus it has two neutrons and one proton.
Production and isolation methods
Laboratory and industrial methods for producing hydrogen are very different. So, in small quantities, gas is obtained mainly through reactions in which minerals are involved, and large-scale production uses organic synthesis to a greater extent.
The following chemical interactions are used in the laboratory:
- The reaction of alkali and alkaline earth metals with water to produce alkali and the desired gas.
- The electrolysis of an aqueous electrolyte solution, H 2 โ is released at the anode, and oxygen is released at the cathode.
- The decomposition of alkali metal hydrides with water, the products are alkali and, accordingly, H 2 โ gas.
- The interaction of dilute acids with metals with the formation of salts and H 2 โ.
- The action of alkalis on silicon, aluminum and zinc also contributes to the evolution of hydrogen in parallel with the formation of complex salts.
In the industrial interest, gas is obtained by methods such as:
- Thermal decomposition of methane in the presence of a catalyst to its constituent simple substances (350 degrees reaches a value such as temperature) - hydrogen H 2 โ and carbon C.
- Passing vaporous water through coke at 1000 degrees Celsius with the formation of carbon dioxide CO 2 and H 2 โ (the most common method).
- Conversion of gaseous methane on a nickel catalyst at temperatures as high as 800 degrees.
- Hydrogen is a by-product of the electrolysis of aqueous solutions of potassium or sodium chlorides.
Chemical interactions: general
The physical properties of hydrogen largely explain its behavior in the processes of reaction with a particular compound. The valency of the hydrogen is 1, since it is located in the first group in the periodic table, and the degree of oxidation is different. In all compounds, except hydrides, hydrogen in organic matter = (1+), in molecules of the type , 2 , 3 - (1-).
A hydrogen gas molecule formed by creating a generalized electron pair consists of two atoms and is quite stable energetically, which is why under normal conditions it is somewhat inert and reacts when normal conditions change. Depending on the degree of oxidation of hydrogen in other substances, it can act both as an oxidizing agent and a reducing agent.
Substances with which it reacts and which hydrogen forms
Elemental interactions with the formation of complex substances (often at elevated temperatures):
- Alkaline and alkaline earth metal + hydrogen = hydride.
- Halogen + H 2 = hydrogen halide.
- Sulfur + hydrogen = hydrogen sulfide.
- Oxygen + H 2 = water.
- Carbon + hydrogen = methane.
- Nitrogen + H 2 = ammonia.
Interaction with complex substances:
- Obtaining synthesis gas from carbon monoxide and hydrogen.
- Reduction of metals from their oxides using H 2 .
- Hydrogen saturation of unsaturated aliphatic hydrocarbons.
Hydrogen bond
The physical properties of hydrogen are such that they, when combined with an electronegative element, form a special type of bond with the same atom from neighboring molecules having lone electron pairs (for example, oxygen, nitrogen and fluorine). The clearest example on which it is better to consider such a phenomenon is water. It can be said to be stitched with hydrogen bonds, which are weaker than covalent or ionic ones, but due to the fact that there are many of them, they have a significant effect on the properties of the substance. In fact, a hydrogen bond is an electrostatic interaction that binds water molecules into dimers and polymers, justifying its high boiling point.
Hydrogen in the composition of mineral compounds
The composition of all inorganic acids includes a proton - a cation of an atom such as hydrogen. A substance whose acid residue has an oxidation state greater than (-1) is called a polybasic compound. It contains several hydrogen atoms, which makes dissociation in aqueous solutions multi-stage. Each subsequent proton breaks away from the acid residue more and more difficult. The quantitative content of hydrogen in the medium determines its acidity.
Hydrogen also contains hydroxyl groups of the bases. In them, hydrogen is connected to an oxygen atom, as a result, the oxidation state of this alkali residue is always equal to (-1). The content of hydroxyls in the medium determines its basicity.
Application in human activities
Cylinders with the substance, as well as containers with other liquefied gases, such as oxygen, have a specific appearance. They are painted a dark green color with a bright red inscription "Hydrogen". Gas is pumped into a cylinder under a pressure of about 150 atmospheres. The physical properties of hydrogen, in particular the lightness of the gaseous state of aggregation, are used to fill aerostats, balloons, etc. in mixtures with helium.
Hydrogen, the physical and chemical properties of which people learned to use many years ago, is currently involved in many industries. Most of it goes to the production of ammonia. Hydrogen is also involved in the production of metals (hafnium, germanium, gallium, silicon, molybdenum, tungsten, zirconium and others) from oxides, acting in the reaction as a reducing agent, hydrocyanic and hydrochloric acids, methyl alcohol, and also artificial liquid fuel. The food industry uses it to turn vegetable oils into solid fats.
The chemical properties and use of hydrogen in various processes of hydrogenation and hydrogenation of fats, coal, hydrocarbons, oils and fuel oil were determined. With it, precious stones, incandescent lamps are produced, metal products are forged and welded under the influence of an oxygen-hydrogen flame.