On the periodic table, the element whose name comes from the Greek word for pale green is chlorine.
Chlorine has the chemical symbol Cl and atomic number 17. Its name comes from the Ancient Greek word chloros, meaning pale green, a reference to the color of chlorine gas. Chlorine is a halogen and appears in group 17 of the periodic table.
In its elemental form, chlorine is a yellow-green gas with a sharp odor and significant toxicity. Chemists and public-health systems use chlorine compounds for disinfection because they can destroy many harmful microorganisms in drinking water and swimming pools.
Chlorine is not the same as chloride. Chloride is the negatively charged ion formed when chlorine gains an electron, and it is part of ordinary table salt, sodium chloride. The other halogens—fluorine, bromine, iodine, and astatine—also occupy group 17, but their names and characteristic colors differ.