What is Chlorine?
{{Infobox chlorine}} [[File:Chlorine-sample.jpg|thumb|Chlorine gas in a tube]] '''Chlorine''' ([[chemical symbol]] '''Cl''') is a [[chemical element]]. Its [[atomic number]] (which is the number of [[protons]] in it) is 17, and its [[atomic mass]] is 35.45. It is part of the 7th column ([[halogen]]s) on the [[periodic table]] of elements. ==Properties== ===Physical properties=== Chlorine is a very irritating and greenish-yellow gas. It has a strong, bleach-like smell. It is toxic and bad for you. It can be made into a liquid when cooled. It is heavier than air. ===Chemical properties=== Chlorine is highly reactive. It is more reactive than bromine but less reactive than fluorine. It reacts with most things to make chlorides. It can even burn things instead of oxygen. It dissolves in water to make a mixture of [[hypochlorous acid]] and [[hydrochloric acid]]. The more [[acid]]ic it is, the more chlorine is made; the more [[base (chemistry)|basic]] it is, the more hypochlorous acid (normally turned into hypochlorite) and hydrochloric acid (normally turned into chlorides) are there. Chlorine reacts with [[bromide]]s and [[iodide]]s to make bromine and [[iodine]]. ===Chlorine compounds=== {{see also|Category:Chlorine compounds}} Chlorine exists in several oxidation states: -1, +1, +3, +4, +5, and +7. The -1 state is most often in [[chloride]]. Chlorides are not reactive. Compounds containing chlorine in its +1 oxidation state are [[hypochlorite]]s. Only one is common. They are a strong [[oxidizing agent]], as are all + oxidation state compounds. +3 is in [[chlorite]]s. +4 is in [[chlorine dioxide]], a common chlorine compound that is not a chloride. +5 is in [[chlorate]]s. +7 is in [[perchlorate]]s. Hypochlorites are most reactive, while perchlorates are the least reactive. Many [[organic chemistry|organic]] compounds have chlorine in them. [[Freon]] has chlorine in it. PVC (poly-vinyl chloride), a common plastic, has chlorine in it. Chlorine oxides can be made, but most of them are very reactive and unstable.