Chlorine is a chemical element with symbol Cl and atomic number 17. It also has a relative atomic mass of 35.5. Chlorine is in the halogen group (17) and is the second lightest halogen following fluorine.
Three reasons Chlorine stands out
- 1
Used to disinfect water and as a bleach.
- 2
It was used as a deadly chemical weapon during World War I.
- 3
It is a key ingredient in PVC plastic, one of the most widely produced synthetic plastics in the world.
A poison that made water safer
Chlorine gas is corrosive and dangerous, yet dilute chlorine chemistry transformed public health by controlling microbes in drinking water. Chloride—the element after gaining an electron—is far less aggressive and is essential in body fluids and table salt. The difference illustrates how dramatically chemical form changes risk.