Bromine

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MELTING POINT: −7.3°C
BOILING POINT : 59°C
DENSITY : 3.12 g/cm ³ (liq. at 20°C)
MOST COMMON IONS : Br ⁻ , BrO ⁻ , BrO ₃ ⁻ , BrO ₄ ⁻

Bromine is a member of a family of elements known as halogens that are found in group 7A of the Periodic Table. Bromine was discovered in 1826 in Montpellier, France, by French chemist Antoine J. Balard.

Bromine is one of two elements (the other being mercury) that is liquid at normal temperatures. As with the other halogens, bromine is very reactive, corrosive, and poisonous. Both the liquid and vapor of bromine are deep red in color. Bromine has a pungent, irritating odor that is the source of the element's name (the Greek word bromos means "stench").

Elemental bromine is a diatomic molecule (Br ₂ ). Bromine will combine with most other elements. Reaction with metallic elements leads to salts such as silver bromide (AgBr), in which the bromine atom has a −1 charge and oxidation number. Bromine forms many interesting covalent compounds as well, including two oxides: bromine (IV) oxide (BrO ₂ ) and bromine (I) oxide (Br ₂ O).

Bromine is produced commercially from natural brines and from sea-water either by electrolysis or with displacement by chlorine, a somewhat more reactive halogen. The concentration of bromine in seawater is approximately 67 parts per million (ppm) by weight; it is found in Earth's crust at an average level of 3 ppm.

Bromine compounds have a variety of uses. Methyl bromide (CH ₃ Br) is a common agricultural soil fumigant; other bromohalocarbon compounds have been used as refrigerants and fire suppressants. Inorganic bromides are important components of photographic emulsions. Bromine reacts with liquid water to produce hypobromite ion (BrO ⁻ ), a powerful bleaching agent. There are also many dyes and pharmaceutical agents that contain bromine.

SEE ALSO Halogens .

John Michael Nicovich

Bibliography

Lide, David R., ed. (2003). The CRC Handbook of Chemistry and Physics , 84th edition. Boca Raton, FL: CRC Press.

Internet Resources

Winter, Mark. "Bromine." The University of Sheffield and WebElements Ltd., U.K. Available from http://www.webelements.com .