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.

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

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]

AcOBr exists. Astatine bromide has the chemical formula AtBr.

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]

"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]