Periodic Table
17
Cl
35.45
Chlorine
HalogenGreenish-yellow toxic gas; strong oxidiser; Cl has higher electron affinity than F.
Electronic Configuration
[Ne] 3s² 3p⁵or1s² 2s² 2p⁶ 3s² 3p⁵
Electron shells
2e⁻n=1
8e⁻n=2
7e⁻n=3
Properties
Atomic number
17
Atomic mass
35.45 u
Category
Halogen
Block / Group / Period
p · 17 · 3
Valence electrons
7
Oxidation states
-1 to +7
Electronegativity
3.16
Atomic radius
79 pm
Ionization energy
1251 kJ/mol
Electron affinity
349 kJ/mol
Melting point
172 K / -101 °C
Boiling point
239 K / -34 °C
Density
0.003214 g/cm³
State at 25 °C
gas
JEE / NEET notes
- Highest electron affinity of all elements.
- Disproportionates in cold/hot alkali differently.
- Bleaching by oxidation (permanent).
- Oxidising power: F₂ > Cl₂ > Br₂ > I₂.
Uses
Water disinfection · Bleaching · PVC · HCl manufacture
Important compounds
HClNaClCl₂O₇HClO₄
Personal Notes
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