Chlorine is a chemical element with the symbol Cl and atomic number 17. Chlorine is a yellow-green gas at room temperature. It is an extremely reactive element and a strong oxidant, which makes it useful in a wide variety of industrial and commercial applications such as bleach, disinfectants, and water treatment. Chlorine is also an essential nutrient and is used in the production of many essential compounds such as proteins, enzymes, and hormones.
Common chlorine compounds include sodium chloride (NaCl), potassium chloride (KCl), and hydrochloric acid (HCl). Chlorine can also form compounds with other elements, such as carbon (CCl4), silicon (SiCl4) and phosphorus (PCl3). These compounds are used in a variety of industrial processes, such as the production of PVC and chlorofluorocarbons (CFCs).