. Group (Halogen group) elements: . . Chlorine Occurrence: The halogens are present in combined form as they are highly reactive.
The main source of fluorine is fluorspar or fluorite. The other ores of fluorine are cryolite, fluroapatite. The main source of chlorine is sodium chloride from sea water. Bromides and iodides also occur in sea water.
Physical properties: The common physical properties of the group elements are listed in the table. XII XII - - - - Table . Physical properties of group elements Property Fluorine Chlorine Bromine Iodine Astatine Physical state at K Gas Gas Liquid Solid Solid Atomic Number Isotopes F Cl, Cl Br I At, At Atomic Mass (g.mol - at K) . .
. . Electronic configuration [He]2s 2p [Ne]3s 3p [Ar]3d 4s 4p [Kr]4d 5s 5p [Xe] 4f 5d 6s 6p Atomic radius (Å) . .
. . . Density (g.cm - at K) .
x - . x - . . - Melting point (K) Boiling point (K) Properties: Chlorine is highly reactive hence it doesn’t occur free in nature.
It is usually distributed as various metal chlorides. The most important chloride is sodium chloride which occurs in sea water. Preparation: Chlorine is prepared by the action of conc. sulphuric acid on chlorides in presence of manganese dioxide.
4NaCl + MnO + 4H SO Cl + MnCl + 4NaHSO + 2H O It can also be prepared by oxidising hydrochloric acid using various oxidising agents such as manganese dioxide, lead dioxide, potassium permanganate or dichromate. PbO + 4HCl PbCl + 2H O + Cl MnO + 4HCl MnCl + 2H O + Cl 2KMnO + 16HCl 2KCl + 2MnCl + 8H O + 5Cl K Cr O + 14HCl 2KCl + 2CrCl + 7H O + 3Cl When bleaching powder is treated with