Chlorine (Cl)
Stable isotopes of chlorine available from ISOFLEX
| Isotope | Z(p) | N(n) | Atomic Mass | Natural Abundance | Enrichment Level | Chemical Form |
| Cl-35 | 17 | 18 | 34.96885271 | 75.78% | 99.00% | Sodium Chloride |
| Cl-37 | 17 | 20 | 36.96590260 | 24.22% | 98.00% | Sodium Chloride |
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Chlorine was discovered in 1774 by Carl William Scheele. Its name derives from the Greek word chloros, meaning “pale green.”
A greenish-yellow gas with a suffocating odor, chlorine combines directly with nearly all other elements. It becomes a pale yellow crystal at -101.5 ºC. It is moderately soluble in water. It has known oxidation states from -1 to +7. It occurs as a diatomic molecule Cl2, containing a single covalent bond in which the Cl-Cl bond distance is 1.99 Å.
Chlorine is a respiratory irritant that was used in war as early as 1915. Today, much of the chlorine supply is used in the manufacture of chlorinated cleaning compounds, pulp bleaching, disinfectants and textile processing. It is also used in the production of safe drinking water all over the world.
Properties of Chlorine
| Name | Chlorine |
| Symbol | Cl |
| Atomic number | 17 |
| Atomic weight | 35.452 |
| Standard state | Gas at 298 ºK |
| CAS Registry ID | 7782-50-5 |
| Group in periodic table | 17 |
| Group name | Halogen |
| Period in periodic table | 3 |
| Block in periodic table | p-block |
| Color | Greenish-yellow |
| Classification | Nonmetallic |
| Melting point | -101.5 ºC |
| Boiling point | -34.04 ºC |
| Thermal conductivity | 0.0089 W/(m·K) |
| Electrical resistivity | 10-8 Ω·m |
| Electronegativity | 3.16 |
| Heat of vaporization | 10.2 (per mole Cl atoms) kJ·mol-1 |
| Heat of fusion | 3.2 (per mole Cl atoms) kJ·mol-1 |
| Density | 2.03 g/cm3 |
| Electron configuration | [Ne]3s23p5 |
| Most common oxidation state | 2 |
