Each chemical element in the periodic table of Mendeleyev on the is unique. However, among them a specific place is held by hydrogen - it the first in the list, the most widespread in the Universe. Hydrogen was widely used in various spheres of activity of the person for this reason to study its chemical properties so important.
Hydrogen as chemical element
Hydrogen is an element of the first group of the main subgroup and also the seventh group of the main subgroup in the first small period. This period consists of only two atoms: helium and the element considered by us. Let's describe the main features of provision of hydrogen in a periodic system.
- Serial number of hydrogen - 1, quantity of electrons same, respectively, protons as much. Atomic mass - 1.00795. There are three isotopes of this element with mass numbers 1, 2, 3. However properties of each of them very strongly differ as increase in weight even on unit for hydrogen is double at once.
- The fact that at the external power level it contains only one electron allows to show successfully to it both oxidizing, and recovery properties. Besides, after return of an electron it has free orbital which takes part in formation of chemical bonds on the donorno-acceptor mechanism.
- Hydrogen is a strong reducer. Therefore the first group of the main subgroup where he heads the most active metals - alkaline is considered its main place.
- However in interaction with strong reducers, such as, for example, metals, it can be also oxidizer, accepting an electron. These connections received the name of hydrides. On this sign he heads subgroup of halogens with which he is similar.
- Thanks to absolutely small atomic mass, hydrogen is considered the easiest element. Besides, its density is also very small therefore it is also an ease standard.
Thus, it is obvious that atom of hydrogen is an element, absolutely unique, unlike all others. Therefore, its properties too the special, and formed simple and complex substances are very important.
Physical properties
Physical parameters hydrogen has the following:
- Boiling temperature - (-252,76 0C).
- Melting temperature - (-259,2 0C).
- In the designated interval of temperatures is the colourless liquid which does not have a smell.
- With very high pressure there are snegoobrazny crystals of solid hydrogen.
- Under certain conditions (high pressure and low temperatures) it is capable to pass into a metal state.
- It is almost insoluble in water therefore collecting by method of replacement of water is possible when receiving in vitro.
- Under usual conditions hydrogen is the gas which does not have a smell, color and taste.
- Is combustible and explosive substance.
- It is well dissolved in metals as it is capable to diffuse through their thickness.
- Approximately by 14.5 times this gas is lighter than air.
Crystal lattice of simple substance molecular, communications weak therefore easily collapse.
Chemical properties
As it was already told above, hydrogen is capable to show both recovery, and oxidizing properties. Possible oxidation levels of element +1;-1. Therefore it is often used in the industry for syntheses and various reactions.
Oxidizing properties of hydrogen
- Interaction with active metals (alkaline and alkaline-earth) under usual conditions leads to formation of the solepodobny connections called hydrides. For example: LiH, CaH2, KH, MgH2 and other.
- Connections with low-active metals under the influence of high temperatures or strong illumination (photochemical initiation of reactions) also form hydrides.
Recovery properties of hydrogen
- Interaction under usual conditions only with fluorine (as strong oxidizer). Fluorine hydride or fluoric HF acid is as a result formed.
- Interaction practically with all nonmetals, but under certain rather severe conditions. Examples of connections: H2S, NH3, H2O, PH3, SiH4 and other.
- Restores metals from their oxides to simple substances. It is one of industrial ways of receiving metals which is called a vodorodotermiya.
Separately it is necessary to allocate reactions which are used in organic syntheses. They are called hydrogenation - saturation by hydrogen and dehydrogenation, that is its otshchepleniye from a molecule. On the basis of these ways of transformations receive a set of hydrocarbons and other organic compounds.
Stay in the nature
Hydrogen is the most widespread substance on our planet and beyond its limits. Practically all interstellar space and stars consist of this connection. In space it can exist in the form of plasma, gas, ions, atoms, molecules. There are several different types on density of the clouds consisting of this substance. If to speak about distribution it is concrete in earth crust, then hydrogen is on the second place on number of atoms after oxygen, it about 17%. In a free look meets seldom, only in insignificant quantities as a part of dry air. The most widespread connection of this element - water. In its structure it also meets on the planet. Also hydrogen is an obligatory component of any living organism. And in a human body 63% fall to the share of this atom. Hydrogen is an organogenic element therefore forms molecules of proteins, fats, carbohydrates and nucleinic acids and also many other vital connections.
Receiving
There are different ways of receiving the gas considered by us. Several industrial and laboratory options of synthesis belong to them. Industrial ways of receiving hydrogen:
- Steam conversion of methane.
- Coal gasification - process means heating of coal to 1000 0C therefore hydrogen and high-carbon coal is formed.
- This method can be used only for water solutions of various salts as fusions do not lead to discharge of water on the cathode.
Laboratory ways of receiving hydrogen:
- Hydrolysis of hydrides of metals.
- Effect of the diluted acids on active metals and average activity.
- Interaction of alkaline and alkaline-earth metals with water.
To collect the formed hydrogen, it is necessary to hold a test tube turned upside down. This gas cannot be collected as, for example, carbon dioxide. It is hydrogen, it is much lighter than air. Quickly disappears, and in large numbers at mixture with air blows up. Therefore it is necessary to overturn a test tube. After its filling it needs to be closed a rubber stopper. To check purity of collected hydrogen, it is necessary to bring the lit match to a neck. If cotton deaf and silent - means gas clean, with the minimum impurity of air. If loud and whistling - dirty, with a big share of foreign components.
Fields of use
At combustion of hydrogen so large amount of energy (warmth) is emitted that this gas is considered the most favorable fuel. Besides eco-friendly. However today its application is in the field limited. It is connected with unreasoned up to the end and not solved problems of synthesis of pure hydrogen which would be suitable for use as fuel in reactors, engines and portable devices and also heating coppers of houses. Ways of receiving this gas rather expensive therefore before it is necessary to develop a special method of synthesis. Such which will allow to receive a product in large volume and with the minimum expenses.
It is possible to allocate several main areas in which the gas considered by us finds application.
- Chemical syntheses. On the basis of hydrogenation receive soaps, margarine, plastic. With the participation of hydrogen, methanol and ammonia and also other connections is synthesized.
- In the food industry - as E949 additive.
- Aviation industry (rocket production, aircraft construction).
- Power industry.
- Fuel of an eco-friendly look.
It is obvious that hydrogen is also important, as well as is spread in the nature.