(i) Occurrence : It mainly occurs in sea water and salt lakes as NaBr, KBr and MgBr₂ .

(ii) Preparation: On a commercial scale, bromine is prepared either from sea water (containing NaBr, KBr and MgBr₂) or the mother liquor (containing MgBr₂ ) left after crystallisation of chlorides from carnallite. On passing Cl₂ gas through these solutions, bromides get oxidised to bromine which is cooled and condensed to Br₂ liquid.

2Br^– + Cl₂ ———> 2Cl^– + Br₂

In the laboratory, bromine can be prepared by heating NaBr with MnO₂ and conc. H₂SO₄ .

It is also obtained by adding HCl to a mixture containing potassium bromide and potassium bromate.

2NaBr + MnO₂ + 3H₂SO₄ ——> 2 NaHSO₄ + MnSO₄ + 2H₂O + Br₂

(iii) Properties : Bromine is a reddish brown heavy liquid.

Its reaction with water, oxidising and bleaching action, reaction with alkalies, NH₃ , metals and non metals are similar to that of chlorine. Br₂ oxidises only iodide ions to I₂ . Bromine water reacts with mercuric oxide to form mercury oxy bromide