2007 Schools Wikipedia Selection. Related subjects: Chemical elements
|Name, Symbol, Number||bromine, Br, 35|
|Group, Period, Block||17, 4, p|
solid: metallic luster
|Atomic mass||79.904 (1) g/mol|
|Electron configuration||[Ar] 3d10 4s2 4p5|
|Electrons per shell||2, 8, 18, 7|
|Density (near r.t.)||(liquid) 3.1028 g·cm−3|
|Melting point||265.8 K
(-7.3 ° C, 19 ° F)
|Boiling point||332.0 K
(58.8 ° C, 137.8 ° F)
|Critical point||588 K, 10.34 MPa|
|Heat of fusion||(Br2) 10.57 kJ·mol−1|
|Heat of vaporization||(Br2) 29.96 kJ·mol−1|
|Heat capacity||(25 °C) (Br2)
|Oxidation states||±1, 5
(strongly acidic oxide)
|Electronegativity||2.96 (Pauling scale)|
| Ionization energies
|1st: 1139.9 kJ·mol−1|
|2nd: 2103 kJ·mol−1|
|3rd: 3470 kJ·mol−1|
|Atomic radius||115 pm|
|Atomic radius (calc.)||94 pm|
|Covalent radius||114 pm|
|Van der Waals radius||185 pm|
|Electrical resistivity||(20 °C) 7.8×1010 Ω·m|
|Thermal conductivity||(300 K) 0.122 W·m−1·K−1|
|Speed of sound||(20 °C) ? 206 m/s|
|CAS registry number||7726-95-6|
Bromine ( IPA: /ˈbrəʊmiːn/, Greek: βρωμος, brómos, meaning "stench"), is a chemical element in the periodic table that has the symbol Br and atomic number 35. A halogen element, bromine is a red volatile liquid at standard room temperature which has a reactivity between chlorine and iodine. This element is corrosive to human tissue in a liquid state and its vapors irritate eyes and throat. Bromine vapors are very toxic upon inhalation.
Bromine is the only liquid nonmetallic element at room temperature and one of five elements on the period table that are liquid at or close to room temperature. The pure chemical element has the physical form of a diatomic molecule, Br2. It is a heavy, mobile, reddish-brown liquid, that evaporates easily at standard temperature and pressures in a red vapor (its colour resembles nitrogen dioxide) that has a strong disagreeable odour resembling that of chlorine. A halogen, bromine resembles chlorine chemically but is less active. It is more active than iodine, however. Bromine is slightly soluble in water, and highly soluble in carbon disulfide, aliphatic alcohols (such as methanol), and acetic acid. It bonds easily with many elements and has a strong bleaching action.
Bromine is highly reactive and is a powerful oxidizing agent in the presence of water. It reacts vigorously with amines, alkenes and phenols as well as aliphatic and aromatic hydrocarbons, ketones and acids (these are brominated by either addition or substitution reactions). With many of the metals and elements, anhydrous bromine is less reactive than wet bromine; however, dry bromine reacts vigorously with aluminium, titanium, mercury as well as alkaline earth metals and alkaline metals.
Elemental bromine is used to manufacture a wide variety of bromine compounds used in industry and agriculture. Traditionally the largest use of bromine was in the production of 1,2-dibromoethane which in turn was used as a gasoline anti- knock agent for leaded gasolines before they were largely phased out due to environmental considerations.
Bromine is also used in the manufacture of fumigants, brominated flame-retardants, water purification compounds, dyes, medicines, sanitizers, inorganic bromides for photography, etc. It is also used to form intermediates in organic synthesis, where it is preferred to iodine due to its much lower cost.
Bromine is used to make brominated vegetable oil, which is used as an emulsifier in many citrus-flavored soft drinks.
Aqueous bromine is orange and can be used in tests for alkenes and phenols.
- When added to an alkene it will lose its colour as it reacts forming a colorless bromoalkane. For example, reaction with ethylene will produce 1,2-dibromoethane.
- When added to phenol a white precipitate, 2,4,6-tribromophenol, will form. With aniline, 2,4,6 tribromoaniline will precipitate (even in water)
Bromine was discovered by Antoine Balard at the salt marshes of Montpellier in 1826 but was not produced in quantity until 1860. The French chemist and physicist Joseph-Louis Gay-Lussac suggested the name bromine due to the characteristic smell of the vapors.
Bromine occurs in nature as bromide salts in very diffuse amounts in crustal rock. Due to leaching, bromide salts have accumulated in sea water (85 ppm), and may be economically recovered from brine wells and the Dead Sea (up to 5000 ppm).
Approximately 500 million kilograms ($350 million USD) of bromine are produced per year (2001) worldwide with the United States and Israel being the primary producers. The largest bromine reserve in the United States is located in Columbia and Union County, Arkansas.
Elemental bromine is a strong irritant and, in concentrated form, will produce painful blisters on exposed skin and especially mucous membranes. Even low concentrations of bromine vapor (from 10 ppm) can affect breathing, and inhalation of significant amounts of bromine can seriously damage the respiratory system.
Accordingly, one should always wear safety goggles and ensure adequate ventilation when handling bromine.
Aluminium bromide (AlBr3), ammonium bromide (NH4Br), bromine monofluoride (BrF), bromine pentafluoride (BrF5), bromine trifluoride (BrF3), tetrabromomethane (CBr4), hydrobromic acid (HBr), iron(III) bromide (FeBr3), lithium bromide (LiBr), phosphorus pentabromide (PBr5), phosphorus tribromide (PBr3), potassium bromide (KBr), potassium bromate (KBrO3), silver bromide (AgBr), sodium bromide (NaBr), sodium bromate (NaBrO3).