Bromine

Vapor pressure
35	selenium ← bromine → krypton
	periodic table
General
Name, Symbol, Number	bromine, Br, 35
Chemical series	halogens
Group, Period, Block	17, 4, p
Appearance	gas/liquid: red-brown; solid: metallic luster ;
Atomic mass	79.904(1) g/mol
Electron configuration	[Ar] 3d10 4s2 4p5
Electrons per shell	2, 8, 18, 7
Physical properties
Phase	liquid
Density (near r.t.)	(liquid) 3.1028 g/cm³
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
Heat of vaporization	(Br2) 29.96 kJ/mol
Heat capacity	(25 °C) (Br2); 75.69 J/(mol·K)
Atomic properties
Crystal structure	orthorhombic
Oxidation states	±1, 5; (strongly acidic oxide)
Electronegativity	2.96 (Pauling scale)
Ionization energies; (more)	1st: 1139.9 kJ/mol
	2nd: 2103 kJ/mol
	3rd: 3470 kJ/mol
Atomic radius	115 pm
Atomic radius (calc.)	94 pm
Covalent radius	114 pm
Van der Waals radius	185 pm
Miscellaneous
Magnetic ordering	nonmagnetic
Electrical resistivity	(20 °C) 7.8×1010 Ω·m
Thermal conductivity	(300 K) 0.122 W/(m·K)
Speed of sound	(20 °C) ? 206 m/s
CAS registry number	7726-95-6
Notable isotopes

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Bromine (chemical symbol Br, atomic number 35) is a nonmetal that belongs to a group of chemical elements known as halogens. It is the only liquid nonmetallic element at room temperature and one of five elements that are liquid at or close to room temperature.

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.

Occurrence

Given its reactivity, bromine is not found as a free element in nature. Instead, it is found in the form of bromide salts in the Earth's crustal rocks and bromide ions in seawater and brine wells.

Approximately 500 million kilograms (worth about $350 million USD) of bromine are produced per year worldwide (as of 2001), with the United States and Israel being the primary producers. The largest bromine reserve in the United States is located in Columbia and Union Counties in Arkansas.

Discovery

Bromine was discovered at nearly the same time in 1826 by two independent investigators: Antoine Jerome Balard, a French chemist, and Carl Löwig, a student at the University of Heidelberg, Germany. The element, however, was not produced in quantity until 1860. Given the characteristic smell of the vapors, French chemist and physicist Joseph-Louis Gay-Lussac suggested the name bromine, from the Greek word βρωμος (brómos), meaning "stench."

Notable characteristics

In the periodic table, bromine is located in group 17 (former group 7A), the halogen family, between chlorine and iodine. In addition, it lies in period 4, between selenium and krypton.

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 color resembles nitrogen dioxide) that has a strong disagreeable odor 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.

Due to its contribution to ozone depletion in Earth's atmosphere, bromine has been evaluated to have an ozone depletion potential of 60 when compared to chlorine.[1]

Safety

Elemental bromine is a strong irritant and, in concentrated form, produces painful blisters on exposed skin and especially mucous membranes. Even low concentrations of bromine vapor (from 10 parts per million) 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.

Recycling

Given its high cost, bromine is usually recycled rather than disposed of into the environment.

Compounds

A wide range of organic and inorganic compounds contain fluorine. In the case of organic compounds, chemists can replace hydrogen atoms with bromine atoms, thus creating many new products.

The following is a list of inorganic compounds of 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)

Applications

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 color 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)

References
ISBN links support NWE through referral fees

Los Alamos National Laboratory – Bromine

External links

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