Chlorine is a diatomic element that exists as a greenish-yellow colored gas at STP. It is able to dissolve in water to a moderate extent. Once it is dissolved in water, it will interact with water to form hydrochloric acid (HCl). This is why it is toxic when inhaled. The chlorine will dissolve in the mucous that lines your airway, and the HCl produced causes the cells and alveoli that line your lungs to burst, causing lung damage or even death. During WWI, chlorine was reacted with gases like ammonia to produce “mustard gas,” which was one of the biological weapons developed in that war. Chlorine is also unique in that it is the only other gas besides O2 to be able to support the combustion of fuels. name three chemical and three physical properties from above.