Chlorine
Halogen element. Poisonous greenish-yellow gas. Occurs widely in nature as sodium chloride in seawater. Reacts directly with many elements and compounds, strong oxidizing agent. Discovered by Karl Scheele in 1774. Humphrey David confirmed it as an element in 1810.
Gallery
Benjah-bmm27, Public domain, via Wikimedia Commons
Emission spectrum
Physical Propertiesmass · density · phase · crystal
Atomic Mass
35.4500Da
Density
0.0029g/L
Phase (STP)
Gas
Melting Point
171.6K
Boiling Point
239.1K
Molar Heat
0.4790J/(mol·K)
Crystal Structure
ORC
Lattice Constant
6.240Å
Atomic Radiiatomic · covalent · van der Waals
Atomic (Empirical)
100.00pm
Covalent
99.00pm
Van der Waals
175.00pm
Electronic Propertieselectronegativity · ionization · affinity
Electron Configuration
[Ne] 3s2 3p5
Electron Shells
2, 8, 7
Electronegativity
3.16Pauling
Electron Affinity
3.6kJ/mol
1st Ionization Energy
13.0kJ/mol
Oxidation States
-1, +1, +2, +3, +4, +5, +6, +7
Orbital DiagramAufbau · Hund's rule · Pauli exclusion
Full: 1s2 2s2 2p6 3s2 3p5Short: [Ne] 3s2 3p5
Ionization Energies (17 known)
Emission Spectrumvisible range · characteristic spectral lines
Abundanceby mass
Log scale · ppm = parts per million by mass
Biological Role
Major electrolyte as chloride ion. Component of stomach acid (HCl).
Discovery
Discovered By
Carl Wilhelm Scheele
Named By
—
Year
1774
Nuclear Data
Known Isotopes
25
Stable Isotopes
4
Stable Mass Numbers
28, 30, 35, 37
Natural isotopic abundance (IUPAC recommended values)
Isotopes of Cl25 known
| Nuclide | Z | N | Mass (AMU) | Half-life | Decay | Jπ | Abundance |
|---|---|---|---|---|---|---|---|
| 28Clstable | 17 | 11 | 28.030349 | Stable | p (1%) | 1+ | — |
| 29Cl | 17 | 12 | 29.015053 | 5.40 zs | p (1%) | 1/2+ | — |
| 30Clstable | 17 | 13 | 30.005018 | Stable | p (1%) | 3+ | — |
| 35Clstable | 17 | 18 | 34.968853 | Stable | stable (1%) | 3/2+ | 7580.0000% |
| 37Clstable | 17 | 20 | 36.965903 | Stable | stable (1%) | 3/2+ | 2420.0000% |
| 50Cl | 17 | 33 | 50.008266 | Unknown | β⁻, β⁻n, 2n | — | — |
| 51Cl | 17 | 34 | 51.015341 | Unknown | β⁻, β⁻n, 2n | 3/2+ | — |
| 52Cl | 17 | 35 | 52.024004 | Unknown | β⁻, β⁻n, 2n | — | — |
Key Compoundscontaining Cl
NaCl
Sodium Chloride
Common table salt with a face-centered cubic crystal lattice
KCl
Potassium Chloride
An ionic salt used as a potassium supplement, fertilizer ingredient, and salt substitute
HCl
Hydrogen Chloride
A diatomic gas that dissolves in water to form hydrochloric acid, a strong monoprotic acid
C₂H₃Cl
Vinyl Chloride
Chloroethene — the monomer for polyvinyl chloride (PVC), the world's third most produced plastic
CHCl₃
Chloroform
Trichloromethane — a dense, sweet-smelling liquid historically used as an anesthetic (1847)
C₁₄H₉Cl₅
DDT
Dichlorodiphenyltrichloroethane — once the most widely used insecticide
NaClO
Sodium Hypochlorite
The active ingredient in household bleach (typically 3–8% solution)
C₁₆H₁₃ClN₂O
Diazepam
Valium — a benzodiazepine that enhances GABA receptor activity, producing sedative, anxiolytic, muscle relaxant, and anticonvulsant effects
C₂₂H₂₃ClN₂O₂
Loratadine
A second-generation antihistamine (Claritin) that blocks H₁ receptors without crossing the blood-brain barrier significantly, causing minimal drowsiness