Nonmetallic chemical element , chemical symbol Cl, atomic number 17.
It is a toxic, corrosive, greenish yellow gas (as the diatomic molecule Cl 2 ) that severely irritates the eyes and respiratory system (and was used for that purpose as a ion and in the hypochlorite ion, it has valence 1; in the chlorite, chlorate, and perchlorate ions, it has higher valences. Chlorine and its compounds are important industrial materials with myriad uses in the manufacture of other chlorinated compounds (e.g., PVC , hydrochloric acid , ethylene dichloride, trichloroethylene, PCB s), in water purification (municipal systems, swimming pools), in textile industries, in flame retardants, in special batteries , and in food processing. Sodium chloride (table salt) is by far the most familiar of its compounds. See also {{link=bleach">bleach .