All practice pages/Interatomic theory/Diatomics
The molecule
Two chlorine atoms sharing a single bond: a yellow-green gas that kills germs in tap water and killed soldiers in 1915.
A strong oxidizer. Sodium, iron wool and thin metal foils burn in it to make chlorides, and a jar of hydrogen and chlorine explodes when a flash of light hits it. It takes the place of bromine and iodine in their salts, turning a colorless bromide solution orange. The hypochlorous acid it forms in water is what bleaches and disinfects: it destroys the colored parts of dye molecules and the cells of bacteria alike.
Electrolysis of salt water, the chlor-alkali process, gives chlorine at one electrode, hydrogen at the other and sodium hydroxide in the solution: 2NaCl + 2H₂O → Cl₂ + H₂ + 2NaOH. It is one of the largest chemical industries. In a lab, concentrated hydrochloric acid dripped onto manganese dioxide or potassium permanganate gives it off.
Disinfecting drinking water and pools, making bleach (sodium hypochlorite) and making PVC plastic use most of it. About as much again goes into solvents, refrigerants, pesticides, dyes and medicines, many of which contain no chlorine by the time they are finished; the chlorine was a tool along the way.
Toxic. It was the first gas used as a weapon, at Ypres in 1915, and a leaking rail tank car can empty a town. At home, mixing bleach with an acid cleaner or with ammonia releases chlorine or chloramine gas. Never mix cleaning products.