Chemicals/Bromines

Bromine is the third-lightest halogen and is a volatile red-brown liquid at room temperature that evaporates readily to form a similarly coloured vapour. Its properties are intermediate between those of chlorine and iodine.

At standard conditions for temperature and pressure it is a liquid; the only other element that is liquid under these conditions is mercury.

Emissions

Bromine emission spectrum is for 400 nm - 700 nm. Credit: McZusatz.{{free media}}

Gases

Liquid and gas bromine are inside a transparent cube. Credit: Alchemist-hp.{{free media}}

Liquids

Liquid bromine is contained in a safety jar. Credit: W. Oelen.{{free media}}

Bromine is a halogen that is a liquid at room temperature and pressure.

Solids

Like solid chlorine and iodine, solid bromine crystallises in the orthorhombic crystal system, in a layered arrangement of Br2 molecules, where the Br–Br distance is 227 pm (close to the gaseous Br–Br distance of 228 pm) and the Br···Br distance between molecules is 331 pm within a layer and 399 pm between layers (compare the van der Waals radius of bromine, 195 pm); thus, bromine is a very poor conductor of electricity, with a conductivity of around 5 × 10⁻¹³ Ω⁻¹ cm⁻¹ just below the melting point, although this is higher than the essentially undetectable conductivity of chlorine.^[1]

At a pressure of 55 GPa (roughly 540,000 times atmospheric pressure) bromine undergoes an insulator-to-metal transition. At 75 GPa it changes to a face-centered orthorhombic structure. At 100 GPa it changes to a body centered orthorhombic monatomic form.^[2]

Alloys

Silver bromide has the formula AgBr. Credit: Ondřej Mangl.{{free media}}

AcOBr exists. Astatine bromide has the chemical formula AtBr.

Compounds

The simplest compound of bromine is hydrogen bromide, HBr.

Aqueous hydrogen bromide is known as hydrobromic acid, which is a strong acid (pKa = −9) because the hydrogen bonds to bromine are too weak to inhibit dissociation. The HBr/H2O system also involves many hydrates HBr·nH2O for n = 1, 2, 3, 4, and 6, which are essentially salts of bromine anions and hydronium cations. Hydrobromic acid forms an azeotrope with boiling point 124.3 °C at 47.63 g HBr per 100 g solution; thus hydrobromic acid cannot be concentrated beyond this point by distillation.^[1]

Remedy

"Br and Pb were more evenly distributed over the various food groups; the group 'nuts' showed the highest content of Br (about 8 mg/kg), but for Pb such a dominant group could not be indicated."^[3]

Resources

References

↑ ^1.0 ^1.1 Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
↑ Duan, Defang (2007-09-26). "Ab initio studies of solid bromine under high pressure". Physical Review B 76 (10): 104113. doi:10.1103/PhysRevB.76.104113.
↑ W. Van Dokkum; R. H. De Vos; Th. Muys; J. A. Wesstra (1989). "Minerals and trace elements in total diets in the Netherlands". British Journal of Nutrition 61: 7-15. http://journals.cambridge.org/production/action/cjoGetFulltext?fulltextid=862736. Retrieved 2012-03-16.

[Greenwood-1] 1.0 ^1.1 Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.

[Duan-2] Duan, Defang (2007-09-26). "Ab initio studies of solid bromine under high pressure". Physical Review B 76 (10): 104113. doi:10.1103/PhysRevB.76.104113.

[Van-3] W. Van Dokkum; R. H. De Vos; Th. Muys; J. A. Wesstra (1989). "Minerals and trace elements in total diets in the Netherlands". British Journal of Nutrition 61: 7-15. http://journals.cambridge.org/production/action/cjoGetFulltext?fulltextid=862736. Retrieved 2012-03-16.

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