Chlorine
Chlorine (氯, symbol Cl) is chemical element number 17, a Halogen in period 3, group 17 of the periodic table, with a standard atomic weight of about 35.45. Yellow-green gas. Used in water treatment and as the second-most-produced halogen.
Properties
| Atomic number | 17 |
|---|---|
| Symbol | Cl |
| Atomic mass | 35.45 u |
| Category | Halogen |
| Period | 3 |
| Group | 17 |
| Electron configuration | [Ne] 3s² 3p⁵ |
| Electronegativity | 3.16 |
| Covalent radius | 102 pm |
| Density | 0.003214 g/cm³ |
| Melting point | 171.65 K |
| Boiling point | 239.11 K |
| Discovery | Carl Wilhelm Scheele, 1774 |
Overview
Yellow-green gas. Used in water treatment and as the second-most-produced halogen. Element 17, Chlorine (Cl), is a Halogen found in period 3, group 17. As a halogen it is a reactive nonmetal that readily gains one electron to form a −1 ion.
Its electron configuration is [Ne] 3s² 3p⁵, with 7 electrons in the outer shell, and an electronegativity of about 3.16 (Pauling). Around 25 °C it is usually a gas (a very low melting point); it melts near 171.65 K (-101.5 °C), boils near 239.11 K (-34 °C), has a density around 0.003214 g/cm³.
In industry and daily life it turns up in Medical / Pharma and Industrial Gas. Compounds featured on this site include HCl, NaCl and Cl₂. On the safety side, it carries a high hazard rating. It was first described by Carl Wilhelm Scheele in 1774. See more trends in the visualization center.
Electron shells
Electrons per shell: 2 · 8 · 7
Main uses
- Medical / Pharma
- Industrial Gas
Hazard
Compounds containing Chlorine
Data sources
Atomic mass uses IUPAC (CIAAW) standard atomic weights; the covalent radius is from Cordero et al. (2008). Verify on the RSC Periodic Table, PubChem and Wikipedia. Educational reference only.