Chlorine (Cl) - Element 17 | Properties & Electron Configuration
What is Chlorine?
Chlorine (Cl) is element 17, a halogen in period 3, group 17. Its electron configuration is 1s² 2s² 2p⁶ 3s² 3p⁵.
| Atomic Number | 17 |
| Symbol | Cl |
| Atomic Mass | 35.45 u |
| Category | Halogen |
| Period | 3 |
| Group | 17 |
| Block | p |
| Electron Configuration | 1s² 2s² 2p⁶ 3s² 3p⁵ |
| Short Config | [Ne] 3s² 3p⁵ |
| Electronegativity | 3.16 |
| Atomic Radius | 99 pm |
| Ionization Energy | 1251 kJ/mol |
| Electron Affinity | 349 kJ/mol |
| Phase (STP) | Gas |
Electron Configuration
The full electron configuration of Chlorine is 1s² 2s² 2p⁶ 3s² 3p⁵. In noble gas shorthand, this is written as [Ne] 3s² 3p⁵.
Chlorine is a p-block element in group 17, period 3.
Periodic Trends
Electronegativity: Chlorine has a Pauling electronegativity of 3.16. Within group 17, electronegativity generally decreases down the group.
Atomic Radius: 99 pm. Across period 3, atomic radius generally decreases left to right as nuclear charge increases.
Ionization Energy: 1251 kJ/mol. Ionization energy generally increases across a period and decreases down a group.
View all 118 elements with trend overlays for electronegativity, atomic radius, ionization energy, and electron affinity.
Explore Chlorine on the Interactive Periodic TableRelated Topics
Fluorine (F)
Properties of Fluorine - same group as Chlorine
Bromine (Br)
Properties of Bromine - same group as Chlorine
Iodine (I)
Properties of Iodine - same group as Chlorine
Sodium (Na)
Properties of Sodium - same period as Chlorine
Magnesium (Mg)
Properties of Magnesium - same period as Chlorine
Aluminum (Al)
Properties of Aluminum - same period as Chlorine