Bromine is a chemical element of the VII group of the periodic system, its atomic number is 35, its nuclear weight is 79,904, and it belongs to halogens. The bromine atom contains 35 protons, 35 electrons, and 45 neutrons. The atom of Br has 2e at the first energy level, 8e on the second energy level, 18e on the third one, and 7e on the fourth one. Bromine is a strong oxidizer; it oxidizes a sulfite ion to sulfate, a nitrite ion to nitrate, etc.
Natural bromine is represented in a mix of two nuclides with mass numbers 79 (in a mix of 50,56 % on weight) and 81. The configuration of an external electron layer is 4s2p5. In compounds, it shows the oxidation rates —1, +1, +3, +5 and +7 (valences I, III, V and VII), the most characteristic oxidation rates are—1 and +5.
Bromine is located in the fourth period in VIIA group of the periodic table.
The history of its discovery: bromine was discovered during the researches of the French chemist A. Balar in 1825. He allocated dark-brown badly smelling liquid received after washing of seaweed ashes by affecting the aqueous solution with chlorine. He called this liquid received from sea water “a muridy” and sent a message about his discovery to the Parisian Academy of Sciences. The commission created for the verification of this message did not accept Balar’s name of the element and called new element “bromine”. The discovery of bromine made a young and unknown person the outstanding scientist. After publishing Balar’s article, it appeared that bottles with a similar substance waited to be researched by the German chemists K.Levig and Y.Libikh. After they knew they had missed a possibility to discover a new element, Libikh exclaimed: “It was not Balar who discovered bromine, bromine discovered Balar”.
Properties: bromine is a heavy (density 3,1055 g/cm3) red-brown dense liquid with a pungent smell under usual conditions. A melting temperature of bromine is 7,25°C, a boiling temperature is +59,2°C. A standard electrode potential Br2/Br in a water solution is +1,065
Types of compounds: bromine can be dissolved in water better than other halogens, the solution is called a bromic water.
The bromides being in water solutions are linked with chlorine (Cl):
Cl2 + 2NaBr = Br2 + 2NaCl.
Bromine can enter the reaction with sulphur (S), thus S2Br2 is formed; bromine enters the reaction with phosphorus (P) “” PBr3 and PBr5. Bromine also reacts with nonmetals selenium (Se) and tellurium (Te).
Bromine’s reaction with hydrogen (H) proceeds when heating and leads to the formation of hydrobromine. HBr solution in water is a hydrobromic acid. Salts of the hydrobromic acid are bromides (NaBr, MgBr2, AlBr3, etc.).
Bromine does not react with oxygen (O) and nitrogen (N). It forms a large number of various compounds with other halogens. For example, bromine forms unstable BrF3 and BrF5 with fluorine (F), with iodine (I) “” IBr. Interacting with many metals, bromine forms bromides, for example, AlBr3, CuBr2, MgBr2, etc. Tantalum (Ta) and platinum (Pt), to a lesser extent “”silver (Ag), the titan (Ti) and plumbum (Pb) are steady against the effect of bromine.
When heating with a catalyst, bromine reacts with benzene forming a bromobenzene C6H5Br (a replacement reaction).
Bromine interacts with solutions of alkalis and with solutions of sodium carbonates (Na) or potassium (K). The corresponding bromides and bromates are formed, for example:
Br2 + 3Na2CO3 = 5NaBr + NaBrO2 + 3CO2.
Existence in the nature: bromine is a quite rare element on the Earth. Its content on the planet is estimated in 0,37 “¢ 10—4 % (approximately the 50th place). Some plants actively accumulate bromine. First of all, they are beans “” lentils, peas, haricots, and also seaweed. The most part of bromine is concentrated in the sea. It is present in the water of salty lakes and in the underground water-bearing layers as well as in the potash salts and stone salts. There is some bromine in the atmosphere; the content of this element in the air of the seaside areas is always higher than in the areas with a continental climate.
Bromine is a part of a large number of various compounds: bromides of sodium (Na), potassium (K), magnesium (Mg), etc. Such minerals of bromine as a bromargyrite (a bromide of silver (Ag) AgBr) and an embolite (the mixed chloride and bromide of silver (Ag)) are found extremely rarely.
Economic value: bromine is applied when receiving a number of inorganic and organic substances in the analytical chemistry. Compounds of bromine are used as fuel additives, pesticides, burning inhibitors as well as in the photography. Medicines containing bromine are widely known. Calming effects of bromic preparations are based on its ability to strengthen braking processes in the central nervous system. Bromine is used for the production of fighting poison gases. The substances based on bromine are widely applied in the main organic synthesis. It is used for the creation of the additives giving a fire-resistance to plasticity, wood, and textile materials. Solutions of bromides are used in the oil production.
Features of work with bromine: working with bromine, it is necessary to use a protective uniform, a gas mask, and gloves. Bromine concentration of about 0,001 % in the air causes the irritation of the mucous membranes and dizziness. A higher concentration of bromine can lead to spasms of the respiratory tracts as well as asthma.