Among all non-metal chemical elements there is a special series - halogens. These atoms got their name for the special properties that they exhibit in chemical interactions. These include:
- iodine;
- chlorine;
- bromine;
- fluorine.
Chlorine and fluorine are toxic gases with strong oxidizing ability. Under normal conditions, iodine is a crystalline substance of a dark violet color with a pronounced metallic luster. It exhibits the properties of a reducing agent. And what does the fourth halogen look like? What are the properties of bromine, the compounds formed by it and the characteristics of it as an element, and as a simple substance? Let's try to figure it out.
Bromine: general characteristic of the element
As a particle of the periodic system, bromine occupies the cell under serial number 35. Accordingly, its nucleus contains 35 protons, and the electron shell contains the same number of electrons. Outer layer configuration: 4s 2 p 5 .
It is located in group VII, the main subgroup, and is part of halogens - a special group of chemical elements by properties. In total, about 28 different isotopic varieties of this atom are known. Mass numbers range from 67 to 94. There are two known stable and stable, as well as prevailing percentages in nature:
- bromine 79 - its 51%;
- 81 bromine - its 49%.
The average atomic mass of an element is 79.904 units. The degree of oxidation of bromine varies from -1 to +7. It exhibits strong oxidizing properties, but inferior to chlorine and fluorine in them, surpassing iodine.
Discovery story
This element was discovered later than its colleagues in the subgroup. By that time, chlorine and iodine were already known. Who made this discovery? Three names can be called right away, since just so many scientists were able to synthesize a new element almost simultaneously, which later turned out to be the atom under consideration. These names are:
- Antoine Jerome Balard.
- Karl Levig.
- Justus Liebig.
However, it is Balar who is considered the official “father”, since he was the first to not only receive and describe, but also send a new substance to the scientific conference of chemists, which is an unknown element.
Antoine Balard studied the composition of sea salt. Carrying out numerous chemical experiments on it, one day he passed chlorine through a solution and saw that some kind of yellow compound was formed. Taking this as the product of the interaction of chlorine and iodine in solution, he began to further investigate the resulting product. Subjected to the following treatments:
- exposed to ether;
- soaked in potassium hydroxide ;
- treated with pyrolusite;
- aged in a sulfate environment.
As a result, he received a volatile brownish-red liquid with an unpleasant odor. This was bromine. He then conducted a thorough study of the physical and chemical characteristics of this substance. After sent a report on it, described the properties of bromine. The name that Balar gave the element was murid, but it did not take root.
Today's common name for this atom is bromine, which is translated from Latin as "smelly," "fetid." This is fully confirmed by the properties of its simple substance. The year of discovery of the element is 1825.
Possible oxidation states of bromine
These can be called a few. Indeed, due to its electronic configuration, bromine can exhibit both oxidizing and reducing properties, with a clear predominance of the former. There are five possible options:
- -1 - the lowest degree of oxidation of bromine;
- +1
- +2;
- +3;
- +5;
- +7.
In nature, there are only those compounds in which the element is in a negative value. +7 - the maximum degree of oxidation of bromine. He manifests it in the composition of bromic acid HBrO 4 and its salts of bromates (NaBrO 4 ). In general, this degree of oxidation of bromine is extremely rare, as is +2. And here are the connections with -1; +3 and +5 are very common and are important not only in the chemical industry, but also in medicine, technology and other sectors of the economy.
Bromine as a simple substance
Under ordinary conditions, the element under consideration is a diatomic molecule, but it is not a gas, but a liquid. Very poisonous, smoking in the air and emitting an extremely unpleasant odor. Even vapors in low concentrations can cause burns on the skin and irritation of the mucous membranes of the body. If you exceed the permissible norm, then suffocation and death are possible.
The chemical formula of this liquid is Br 2 . Obviously, the symbol is formed from the Greek name of the element - bromos. The bond between the atoms is single, covalent non-polar. The radius of the atom is relatively large, so bromine reacts quite easily. This allows it to be widely used in chemical syntheses, often as a reagent for the qualitative determination of organic compounds.
In the form of a simple substance, it does not occur in nature, since it easily evaporates in the form of reddish-brown smoke, which has a corrosive effect. Only in the form of various multicomponent systems. The degree of oxidation of bromine in compounds of various kinds depends on which particular element the reaction is with, that is, with which substance.
Physical properties
These characteristics can be expressed in several points.
- Solubility in water is average, but better than other halogens. A saturated solution is called bromine water, it has a reddish-brown color.
- The boiling point of the liquid is +59.2 0 .
- Melting point -7.25 0 C.
- The smell is sharp, unpleasant, suffocating.
- Color - reddish-brown.
- The state of aggregation of a simple substance is a heavy (with a high density), thick liquid.
- Electronegativity on the Polling scale is 2.8.
These characteristics affect the methods for producing this compound, as well as impose obligations to observe extreme caution when working with it.
Chemical properties of bromine
From the point of view of chemistry, bromine behaves in two ways. It exhibits both oxidizing and reducing properties. Like all other elements, it is capable of accepting electrons from metals and less electronegative non-metals. It is a reducing agent with strong oxidizing agents, such as:
- oxygen;
- fluorine;
- chlorine;
- some acids.
Naturally, the degree of oxidation of bromine in this case varies from -1 to +7. What exactly is the element under consideration capable of reacting with?
- With water - as a result, a mixture of acids (hydrobromic and hydrobromic) is formed.
- With various iodides, since bromine is able to displace iodine from its salts.
- With all non-metals directly, except oxygen, carbon, nitrogen and noble gases.
- With almost all metals as a strong oxidizing agent. With many substances, even with ignition.
- In OVR reactions, bromine often promotes the oxidation of compounds. For example, sulfur and sulfites are converted to sulfate ions, iodides to iodine, as a simple substance.
- With alkalis with the formation of bromides, bromates or hypobromates.
Of particular importance are the chemical properties of bromine when it is part of the acids and salts formed by it. In this form, its properties as an oxidizing agent are very strong. Much brighter than that of a simple substance.
Getting
The fact that the substance under consideration is important and significant from the point of view of chemistry confirms the fact of its annual production in the amount of 550 thousand tons. Leading countries for these indicators:
The industrial method for the production of free bromine is based on the treatment of salt solutions of lakes, wells, and seas. Of these, the salt of the desired element is released, which is converted into an acidified form. It is passed through a powerful stream of air or water vapor. Thus, gaseous bromine is formed. Then it is treated with soda ash and get a mixture of sodium salts - bromides and bromates. Their solutions are acidified and have free liquid substance at the outlet.
Laboratory methods of synthesis are based on the displacement of bromine from its salts by chlorine, as a stronger halogen.
Being in nature
In its pure form, the substance we are considering does not occur in nature, since it is a volatile liquid that fumes in air. It is mainly a part of compounds in which the minimum oxidation state of bromine is -1. These are salts of hydrobromic acid - bromides. A lot of this element is accompanied by natural chlorine salts - sylvins, carnallites and others.
Minerals of bromine itself were discovered later than himself. The most common of them are three:
- embolite - a mixture of chlorine and bromine with silver;
- bromarginitis;
- bromosilvinite is a mixture of potassium, magnesium and bromine with bound water (crystalline hydrate).
Also, this element is necessarily a part of living organisms. Its deficiency leads to the emergence of various diseases of the nervous system, disorders, sleep disturbance and memory impairment. In worse cases, it threatens infertility. Fishes, marine life are able to accumulate bromine in significant quantities in the form of salts.
In the earth's crust, its mass content reaches 0.0021%. A lot contains sea water and the earth’s hydrosphere as a whole.
Low oxidation bromine compounds
What is the oxidation state of bromine in its compounds with metals and hydrogen? The lowest that is possible for this element is minus one. It is these compounds that are of the greatest practical interest to humans.
- HBr is hydrogen bromide (gas), or hydrobromic acid. In a gaseous state of aggregation it has no color, but it smells very harsh and unpleasant, it smokes a lot. It has a corrosive effect on the mucous membranes of the body. It is well dissolved in water, forming acid. It, in turn, refers to strong electrolytes, is a good reducing agent. It easily transforms into free bromine under the action of sulfuric, nitric acids and oxygen. It is of industrial importance as a source of bromide ion for the formation of salts with metal cations.
- Bromides - salts of the above acid, in which the degree of oxidation of bromine is also equal to -1. Of practical interest are: LiBr and KBr.
- Organic compounds containing bromide ion.
Highly oxidized compounds
These include several basic substances. The oxidation state of higher bromine is +7, which means that in these compounds it is precisely this which should be manifested.
- Bromic acid - HBrO 4 . The strongest of all acids known for this element, however, it is also the most resistant to attacks of strong reducing agents. This is due to the special geometric structure of the molecule, which in space has the shape of a tetrahedron.
- Perbromates are salts above the designated acid. They are also characterized by the maximum degree of oxidation of bromine. They are strong oxidizing agents, which is why they are used in the chemical industry. Examples: NaBrO 4 , KBrO 4 .
The use of bromine and its compounds
Several areas can be identified in which bromine and its compounds are directly used.
- Dye production.
- For the manufacture of photographic materials.
- As medicines in medicine (bromine salts).
- In the automotive industry, namely as an additive in gasoline.
- Used as an impregnation to lower the flammability of some organic materials.
- In the manufacture of drilling fluids.
- In agriculture in the manufacture of insect-protective sprayers.
- As a disinfectant and disinfectant, including for water.
Biological effect on the body
Both excess and lack of bromine in the body have very unpleasant consequences.
Pavlov was the first to determine the influence of this element on living beings. Animal experiments have shown that prolonged short-term receipt of bromine ions leads to:
- disruption of the nervous system;
- sexual dysfunction;
- miscarriages and infertility;
- reduced growth;
- decrease in hemoglobin level;
- insomnia and so on.
Excessive accumulation in organs and tissues leads to suppression of the brain and spinal cord, various external skin diseases.