Chlorine
- Latin name: Chlorium
- German name: Chlor
- Symbol: Cl
- Atomic number: 17
- Period (row): 3
- Group (column): 17
- Element group: halogen
- Atomic mass: 35.453
- Discovered in: 1774
In the form of chloride ions, chlorine is necessary to all known species of life. Other types of chlorine compounds are rare in living organisms, and artificially produced chlorinated organics range from inert to toxic.