Bromine

Bromine is a halogen with seven valence electrons ([Ar]3d10 4s2 4p5), one short of a noble-gas configuration, so it readily gains an electron to form the bromide ion, Br−. It is a strong oxidizing agent, though weaker than chlorine, which means chlorine can push bromide out of solution as bromine; this is how the element is extracted. Bromine exists as Br2 molecules. Their large electron clouds produce stronger attractive forces than in chlorine, so bromine is a dense, dark red-brown liquid that melts at −7.2 °C and boils at 58.8 °C, giving off choking orange fumes.

Mercury is the only other element that is liquid at room temperature. Bromine is extracted from seawater, which contains about 65 milligrams per liter, and from far richer brines such as the Dead Sea and underground deposits in Arkansas. Its largest uses are brominated flame retardants, dense calcium bromide fluids for drilling oil wells, water disinfection and pharmaceuticals. Methyl bromide, once a major soil fumigant, has been largely phased out under the Montreal Protocol because bromine atoms destroy stratospheric ozone very efficiently.

Discovery

Bromine was discovered independently by two young chemists: Carl Jacob Löwig, who extracted it from mineral spring water at Bad Kreuznach in 1825, and Antoine Jérôme Balard, who found it in brine from the salt marshes of Montpellier in 1826. Balard published first and is usually credited. The name comes from the Greek brōmos, meaning stench, after its sharp, irritating smell.