Atomic number 17
Chlorine
Halogen
Quick facts
- Atomic mass
- 35.450
- Group
- 17
- Period
- 3
- State (STP)
- gas
- Electronegativity
- 3.16
- Common ox. states
- -1, +1, +3, +5, +7
Properties
Electron configuration
[Ne] 3s² 3p⁵
- Ionization energy
- 1251.2 kJ/mol
- Electron affinity
- 349.0 kJ/mol
- Melting point
- 171.65 K (-101.5 °C)
- Boiling point
- 239.11 K (-34.0 °C)
How it bonds
Chlorine forms one bond by gaining or sharing one electron — Cl⁻ in NaCl, single-bonded to almost anything in HCl, CCl₄, ClO⁻. Three lone pairs. With more-electronegative oxygen, chlorine can swing positive (+1, +3, +5, +7 in chlorate, perchlorate, etc.) — the only halogen besides bromine and iodine that does this routinely.