Chlorine is a chemical element with symbol Cl and atomic number 17. Chlorine is in the halogen group (17) and is the second lightest halogen after fluorine. The element is a yellow-green gas under standard conditions, where it forms diatomic molecules. It has the highest electron affinity and the third highest electronegativity of all the elements; for this reason, chlorine is a strong oxidizing agent. Free chlorine is rare on Earth, and is usually a result of direct or indirect oxidation by oxygen.Symbol: Cl
Atomic number: 17
Electron configuration: Ne 3s2 3p5
Boiling Point: -34.04 °C
Atomic mass: 35.453 ± 0.002 u
Discoverer: Carl Wilhelm Scheele