17ClChlorine35.45[Ne] 3s² 3p⁵
diatomic nonmetal
Chlorine
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.
A stylized shell model. Electrons are quantum objects, not particles following these literal paths. Sizes and motion are illustrative.
Electrons by shell
Electron configuration
3s2
3p5
10 is the [Ne] core total across two shells.
At a glance
- Atomic number
- 17
- Atomic mass
- 35.45 u
- Phase
- Gas
- Density
- 3.2 g/L
- Melting point
- 171.6 K
- Boiling point
- 239.11 K
- First ionization energy
- 1,251.2 kJ/mol
- Electronegativity
- 3.16
- Electron affinity
- 348.575 kJ/mol
- Molar heat capacity
- Unavailable
- Period
- 3
- Appearance
- pale yellow-green gas
Conditions and isotopes affect measured properties. Some properties of short-lived elements are predicted. Electronegativity uses the Pauling scale.
Keep exploring
Explore the stories, imagery, and reference data in more depth. Properties with no value in the reference are marked unavailable.