Chlorine diatomic element
Chlorine element is a diatomic, yellow–green gas. It was discovered in 1774 by Carl Wilhelm Scheele. Chlorine(Cl) has high electron affinity, electronegativity (third highest electronegative element of the periodic table) and reacts with nearly all metals, hence acts as a good oxidizing agent.
Chlorine is by far the most common of the halogens in nature, being found in the form of sodium chloride in seawater and rock salt, as well as playing a part in all living organisms. Every kilogram of seawater contains around 30 g of sodium chloride. Twenty–nine million tons or more of chlorine is used throughout the world each year. Chlorine is used as a cheap industrial oxidant in the manufacture of bromine, as bleach and a germicide, but more importantly it is vital for the manufacture of many everyday materials.
Chlorine compounds used as a disinfectant in water treatment
In industry chlorine is produced mostly by electrolysis of brine (a concentrated solution of rock salt in
water), and the associated production of sodium hydroxide and hydrogen, is the basis of the massive chlor–alkali industry.
2 NaCl + 2 H2O → Cl2 + H2 + 2 NaOH
In the laboratory small amounts of chlorine gas can be prepared by combining hydrochloric acid and manganese
dioxide.
MnO2 + 4HCl → MnCl2 + Cl2 + 2H2O
Cl can have oxidation states of −1, +1, +3, +4, +5, +6 and +7. At higher concentrations chlorine gas (elemental chlorine )is poisonous for living organisms.
Chlorine is a very important industrial chemical. Its major use is as a bleaching agent, especially for wood pulp and paper, and also for bleaching cotton cloth. It is used in the preparation of bleaching powder and in the disinfecting water supplies. Solutions of NaOCl are used as household laundry bleaches. Potassium chlorate [KClO3] is used as the oxidizing agent in match sticks and fire works.