The chemical formula for chlorine gas is Cl2. Its molar mass is 70.906 grams per mole. It exists as a yellow-green gas at standard temperature and pressure, and its density is 3.2 grams per liter. Its melting point is -150.7 degrees Fahrenheit, and its boiling point is -29.27 degrees Fahrenheit.
Chlorine gas has an odor similar to common household bleach. It can be dissolved in water; however, it also partially reacts with water to form hydrochloric acid and hypochlorous acid. Chlorine is classified as a halogen, and its negative ion forms salts in combination with positive metal ions. Its best known compound is sodium chloride, which has been used as table salt since ancient times.