The chemical element whose name comes from the Greek word for pale green is chlorine.
Chlorine’s name derives from the Ancient Greek word chloros, meaning pale green, referring to the color of chlorine gas. The element has atomic number 17 and belongs to the halogen group. At room temperature, elemental chlorine is a yellow-green gas made of diatomic molecules, Cl₂.
Swedish chemist Carl Wilhelm Scheele produced chlorine-containing gas in 1774, but he did not recognize it as a new element. Humphry Davy later established that it was an element and named it chlorine in 1810. The gas is highly reactive because chlorine atoms readily gain an electron to form chloride ions.
Chloride compounds are widespread, including sodium chloride in table salt. Carefully controlled chlorine chemistry is also used to disinfect drinking water and swimming pools. Chlorine gas itself is hazardous, so these applications generally rely on compounds or dilute solutions rather than uncontrolled elemental gas.