Name: bromine	Group number: 17
Symbol: Br	Group name: Halogen
Atomic number: 35	Period number: 4
Atomic weight: 79.904 (1)	Block: p-block
CAS Registry ID: 7726-95-6	Voice:
Standard state: liquid at 298 K	Colour: red-brown, metallic lustre when solid
Classification: Non-metallic	Availability:

Isolation

Bromine is available commercially so it is not normally necessary to make it in the laboratory. Bromine also occurs in seawater as the sodium salt but in much smaller quantities than chloride. It is recovered commercially through the treatment of seawater with chlorine gas and flushing through with air. In this treatment, bromide is oxidized to bromine by the chlorine gas. The principle of oxidation of bromide to bromine is shown by the addition of a little chlorine water to aqueous solutions of bromide. These become brown as elemental bromine forms.

2Br^- + Cl₂ 2Cl^- + Br₂

Small amounts of bromine can also be made through the reaction of solid sodium bromide, NaBr, with concentrated sulphuric acid, H₂SO₄. The first stage is formation of HBr, which is a gas, but under the reaction conditions some of the HBr is oxidized by further H₂SO₄ to form bromine and sulphur dioxide. This reaction does not work with the corresponding chlorides and fluorides.

NaBr (s) + H₂SO₄ (l) HBr (g) + NaHSO₄ (s)

2HBr (g) + H₂SO₄ (l) Br₂ (g) + SO₂ (g) + 2H₂O (l)