Crystalline Solid Crystalloid Curie Curium Cyclic Compound Cyclohexane Cyclotron Chlorine , symbol Cl, greenish-yellow gas eous element. The atomic number of chlorine is 17. Free chlorine does not occur in nature, but its compounds are common mineral s, and it is the 20th most abundant element in the earth's crust.
Chlorine is an active element, reacting with water , organic compounds, and many metals .
Chlorine and hydrogen can be kept together in the dark, but react explosively in the presence of light. Chlorine solution s in water are familiar in the home as bleaching agents. Most chlorine is produced by the electrolysis of ordinary salt solution, with sodium hydroxide as a by-product. Because the demand for chlorine exceeds that for sodium hydroxide, some industrial chlorine is produced by treating salt with nitrogen oxides or by oxidizing hydrogen chloride . Chlorine is shipped as a liquid in steel bottles or tank cars.