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Cl 17

Chlorine (Cl)

halogen
Period: 3 Group: 17 Block: p

Gas

Standard Atomic Weight

35.45 u [35.446, 35.457]

Electron configuration

[Ne] 3s2 3p5

Melting point

-101.5 °C (171.65 K)

Boiling point

-34.04 °C (239.11 K)

Density

3.214 kg/m³

Oxidation states

−1, +1, +2, +3, +4, +5, +6, +7

Electronegativity (Pauling)

3.16

Ionization energy (1st)

Discovery year

1774

Atomic radius

100 pm

Details

Name origin Greek: chlôros (greenish yellow).
Discovery country Sweden
Discoverers Carl Wilhelm Scheele

Chlorine is a reactive halogen and a yellow-green diatomic gas, Cl₂, under ordinary conditions. It is a strong oxidizing agent and occurs naturally mainly as chloride salts, especially in seawater and evaporite minerals. Chlorine chemistry is central to water disinfection, inorganic chlorides, chlorinated solvents, polymers, and many industrial oxidation and substitution processes. The element has two stable isotopes, ³⁵Cl and ³⁷Cl.

It is a member of the halogen (salt-forming) group of elements and is obtained from chlorides by the action of oxidizing agents and more often by electrolysis; it is a greenish-yellow gas, combining directly with nearly all elements. At 10°C one volume of water dissolves 3.10 volumes of chlorine, at 30°C only 1.77 volumes.

The name derives from the Greek chloros for "pale green" or "greenish yellow" colour of the element. It was discovered by the Swedish pharmacist and chemist Carl-Wilhelm Scheele in 1774. In 1810, the English chemist Humphry Davy proved it was an element.

Since it combines directly with nearly every element, chlorine is never found free in nature. Chlorine was first produced by Carl Wilhelm Scheele, a Swedish chemist, when he combined the mineral pyrolusite (MnO2) with hydrochloric acid (HCl) in 1774. Although Scheele thought the gas produced in his experiment contained oxygen, Sir Humphry Davy proved in 1810 that it was actually a distinct element. Today, most chlorine is produced through the electrolysis of aqueous sodium chloride (NaCl).

From the Greek word chloro, greenish yellow. Discovered in 1774 by Scheele, who thought it contained oxygen. Chlorine was named in 1810 by Davy, who insisted it was an element.

Read about Chlorine on Wikipedia

Images

Properties

Physical

Atomic radius (empirical) 100 pm
Covalent radius 102 pm
Van der Waals radius 175 pm
Density
Molar volume 0.0187 L/mol
Phase at STP gas
Melting point -101.5 °C
Boiling point -34.04 °C
Thermal conductivity 0.009 W/(m·K)
Specific heat capacity 0.479 J/(g·K)
Molar heat capacity 33.949 J/(mol·K)
Crystal structure orthorhombic

Chemical

Electronegativity (Pauling) 3.16
Electronegativity (Allen) 2.869
Electron affinity
Ionization energy (1st)
Ionization energy (2nd)
Ionization energy (3rd)
Ionization energy (4th)
Ionization energy (5th)
Oxidation states −1, +1, +2, +3, +4, +5, +6, +7
Valence electrons 7
Electron configuration
Electron configuration (semantic)

Thermodynamic

Critical point (temperature) 143.9 °C
Critical point (pressure) 7.991000e+6 Pa
Heat of fusion 0.0664352 eV
Heat of vaporization 0.21153547 eV
Heat of atomization 1.261129 eV
Atomization enthalpy

Nuclear

Stable isotopes 2
Discovery year 1774

Abundance

Abundance (Earth's crust) 145 mg/kg
Abundance (ocean)

Reactivity

N/A

Crystal Structure

Lattice constant a 624 pm

Electronic Structure

Electrons per shell 2, 8, 7

Identifiers

CAS number 7782-50-5
Term symbol
InChI InChI=1S/Cl
InChI Key ZAMOUSCENKQFHK-UHFFFAOYSA-N

Electron Configuration Measured

Ion charge
Protons 17
Electrons 17
Charge Neutral
Configuration Cl: 3s² 3p⁵
Electron configuration
Measured
[Ne] 3s² 3p⁵
1s² 2s² 2p⁶ 3s² 3p⁵
Orbital diagram
1s
2/2
2s
2/2
2p
6/6
3s
2/2
3p
5/6 1↑
Total electrons: 17 Unpaired: 1 ?

Atomic model

Protons 17
Neutrons 18
Electrons 17
Mass number 35
Stability Stable

Isotopes change neutron count, mass, and stability — not the electron configuration of a neutral atom.

Schematic atomic model, not to scale.

Atomic Fingerprint

Emission / Absorption Spectrum

25 / 50 (50 with intensity)
Measured
Emission Visible: 380–750 nm
Source: NIST Atomic Spectra Database Wavelengths in air

Isotope Distribution

3575.7600%3724.2400%Mass numberNatural abundance (%)
Mass numberAtomic mass (u)Natural abundanceHalf-life
35 Stable34.968852682 ± 0.00000003775.7600%Stable
37 Stable36.965902602 ± 0.00000005524.2400%Stable
Measured

Phase / State

1 atm / 101.325 kPa
Gas 25 °C (298.15 K)

Reason: 59.0 °C above boiling point (-34.04 °C)

Melting point -101.5 °C
Boiling point -34.04 °C
Above boiling by 59.0 °C
0 K Current temperature: 25 °C 6000 K
Phase timeline

Schematic, not to scale

Solid
Liquid
Gas
Melting
Boiling
25°C
Solid
Liquid
Gas
Current

Phase transition points

Melting point Literature
-101.5 °C
Boiling point Literature
-34.04 °C
Current phase Calculated
Gas

Transition energies

Heat of fusion Literature
0.0664352 eV

Energy required to melt 1 mol at melting point

Heat of vaporization Literature
0.21153547 eV

Energy required to vaporize 1 mol at boiling point

Density

Reference density Literature
3.214 kg/m³

At standard conditions

Current density Estimated
1.449046 kg/m³

Estimated via ideal gas law at current T

Advanced

Critical point Literature
143.9 °C

Atomic Spectra

Showing 10 of 17 Atomic Spectra. Sorted by ion charge (ascending).

Lines Holdings ?

IonChargeTotal linesTransition probabilitiesLevel designations
Cl I 022199100
Cl II +1292221221
Cl III +2192166166
Cl IV +3734245
Cl V +42766
Cl VI +5111
Cl VII +6282828
Cl VIII +7555
Cl IX +8333
Cl X +9111111
NIST Lines Holdings →

Levels Holdings ?

IonChargeLevels
Cl I 0379
Cl II +1275
Cl III +283
Cl IV +341
Cl V +429
Cl VI +567
Cl VII +647
Cl VIII +729
Cl IX +857
Cl X +915
NIST Levels Holdings →
17 Cl 35.451499999999996

Chlorine — Atomic Orbital Visualizer

[Ne]3s23p5
Energy levels 2 8 7
Oxidation states -1, +1, +2, +3, +4, +5, +6, +7
HOMO 3p n=3 · l=1 · m=-1
Chlorine — Atomic Orbital Visualizer Preview
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17 Cl 35.451499999999996

Chlorine — Crystal Structure Visualizer

Orthorhombic · Pearson N/A
Experimental
Pearson N/A
No crystal structure at standard conditions — gas at 298 K, 1 atm
Solid phase structure at 293 K
Chlorine — Crystal Structure Visualizer Preview
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Ionic Radii

ChargeCoordinationSpinRadius
-16N/A181 pm
+53N/A12 pm
+74N/A8 pm
+76N/A27 pm

Compounds

Cl-
35.450 u
Cl
35.450 u
Cl+
35.450 u
Cl-
35.968 u
Cl-
33.974 u
Cl-
37.968 u
Cl-
36.966 u
Cl
35.968 u

Isotopes (2)

Mass numberAtomic mass (u)Natural abundanceHalf-lifeDecay mode
35 Stable34.968852682 ± 0.00000003775.7600% ± 0.1000%Stable
stable
37 Stable36.965902602 ± 0.00000005524.2400% ± 0.1000%Stable
stable
35 Stable
Atomic mass (u) 34.968852682 ± 0.000000037
Natural abundance 75.7600% ± 0.1000%
Half-life Stable
Decay mode
stable
37 Stable
Atomic mass (u) 36.965902602 ± 0.000000055
Natural abundance 24.2400% ± 0.1000%
Half-life Stable
Decay mode
stable

Spectral Lines

Showing 50 of 207 Spectral Lines. Only spectral lines with measured intensity are shown by default.

Wavelength (nm)IntensityIon stageTypeTransitionAccuracySource
479.4556 nm99000Cl IIemission3s2.3p3.(4S*).4s 5S* → 3s2.3p3.(4S*).4p 5PMeasuredNIST
542.3257 nm99000Cl IIemission3s2.3p3.(4S*).3d 5D* → 3s2.3p3.(4S*).4p 5PMeasuredNIST
489.6783 nm81000Cl IIemission3s2.3p3.(2D*).4s 3D* → 3s2.3p3.(2D*).4p 3FMeasuredNIST
521.7945 nm56000Cl IIemission3s2.3p3.(4S*).4s 3S* → 3s2.3p3.(4S*).4p 3PMeasuredNIST
490.4776 nm47000Cl IIemission3s2.3p3.(2D*).4s 3D* → 3s2.3p3.(2D*).4p 3FMeasuredNIST
481.007 nm29000Cl IIemission3s2.3p3.(4S*).4s 5S* → 3s2.3p3.(4S*).4p 5PMeasuredNIST
491.773 nm26000Cl IIemission3s2.3p3.(2D*).4s 3D* → 3s2.3p3.(2D*).4p 3FMeasuredNIST
507.8267 nm26000Cl IIemission3s2.3p3.(2D*).4s 3D* → 3s2.3p3.(2D*).4p 3DMeasuredNIST
386.0828 nm25000Cl IIemission3s2.3p3.(4S*).4p 5P → 3s2.3p3.(4S*).4d 5D*MeasuredNIST
522.1362 nm23000Cl IIemission3s2.3p3.(4S*).4s 3S* → 3s2.3p3.(4S*).4p 3PMeasuredNIST
544.3375 nm19000Cl IIemission3s2.3p3.(4S*).3d 5D* → 3s2.3p3.(4S*).4p 5PMeasuredNIST
481.948 nm16000Cl IIemission3s2.3p3.(4S*).4s 5S* → 3s2.3p3.(4S*).4p 5PMeasuredNIST
539.2125 nm15000Cl IIemission3s2.3p3.(2D*).4s 1D* → 3s2.3p3.(2D*).4p 1FMeasuredNIST
478.132 nm13000Cl IIemission3s2.3p3.(2P*).4s 3P* → 3s2.3p3.(2P*).4p 3DMeasuredNIST
385.0988 nm10000Cl IIemission3s2.3p3.(4S*).4p 5P → 3s2.3p3.(4S*).4d 5D*MeasuredNIST
499.5473 nm10000Cl IIemission3s2.3p3.(2D*).3d 3F* → 3s2.3p3.(2D*).4p 3DMeasuredNIST
542.3516 nm10000Cl IIemission3s2.3p3.(4S*).3d 5D* → 3s2.3p3.(4S*).4p 5PMeasuredNIST
544.4217 nm10000Cl IIemission3s2.3p3.(4S*).3d 5D* → 3s2.3p3.(4S*).4p 5PMeasuredNIST
385.1374 nm7900Cl IIemission3s2.3p3.(4S*).4p 5P → 3s2.3p3.(4S*).4d 5D*MeasuredNIST
725.6618 nm7500Cl Iemission3s2.3p4.(3P).4s 4P → 3s2.3p4.(3P).4p 4S*MeasuredNIST
545.7037 nm5600Cl IIemission3s2.3p3.(4S*).3d 5D* → 3s2.3p3.(4S*).4p 5PMeasuredNIST
741.4118 nm5000Cl Iemission3s2.3p4.(3P).4s 4P → 3s2.3p4.(3P).4p 2P*MeasuredNIST
386.099 nm4400Cl IIemission3s2.3p3.(4S*).4p 5P → 3s2.3p3.(4S*).4d 5D*MeasuredNIST
476.8651 nm4300Cl IIemission3s2.3p3.(2P*).4s 3P* → 3s2.3p3.(2P*).4p 3DMeasuredNIST
384.5639 nm3900Cl IIemission3s2.3p3.(4S*).4p 5P → 3s2.3p3.(4S*).4d 5D*MeasuredNIST
384.5362 nm3100Cl IIemission3s2.3p3.(4S*).4p 5P → 3s2.3p3.(4S*).4d 5D*MeasuredNIST
380.5174 nm1900Cl IIemission3s2.3p3.(2D*).4p 3D → 3s2.3p3.(2D*).4d 3F*MeasuredNIST
609.468 nm1900Cl IIemission3s2.3p3.(2D*).4s 1D* → 3s2.3p3.(2D*).4p 1PMeasuredNIST
384.5788 nm1500Cl IIemission3s2.3p3.(4S*).4p 5P → 3s2.3p3.(4S*).4d 5D*MeasuredNIST
391.3866 nm1500Cl IIemission3s2.3p3.(2D*).4p 3F → 3s2.3p3.(2D*).4d 3F*MeasuredNIST
380.9459 nm1300Cl IIemission3s2.3p3.(2D*).4p 3D → 3s2.3p3.(2D*).4d 3F*MeasuredNIST
385.1651 nm1200Cl IIemission3s2.3p3.(4S*).4p 5P → 3s2.3p3.(4S*).4d 5D*MeasuredNIST
391.6632 nm1100Cl IIemission3s2.3p3.(2D*).4p 3F → 3s2.3p3.(2D*).4d 3F*MeasuredNIST
386.1378 nm1000Cl IIemission3s2.3p3.(4S*).4p 5P → 3s2.3p3.(4S*).4d 5D*MeasuredNIST
399.1367 nm700Cl IIIemission3s2.3p2.(3P).3d 4P → 3s2.3p2.(3P).4p 4P*MeasuredNIST
401.8351 nm600Cl IIIemission3s2.3p2.(3P).3d 4P → 3s2.3p2.(3P).4p 4P*MeasuredNIST
405.893 nm600Cl IIIemission3s2.3p2.(3P).3d 4P → 3s2.3p2.(3P).4p 4P*MeasuredNIST
410.4082 nm500Cl IIIemission3s2.3p2.(3P).3d 4P → 3s2.3p2.(3P).4p 4P*MeasuredNIST
410.6764 nm500Cl IIIemission3s2.3p2.(3P).3d 4P → 3s2.3p2.(3P).4p 4P*MeasuredNIST
436.3268 nm100Cl Iemission3s2.3p4.(3P).4s 4P → 3s2.3p4.(3P).5p 4D*MeasuredNIST
436.9498 nm100Cl Iemission3s2.3p4.(3P).4s 4P → 3s2.3p4.(3P).5p 2D*MeasuredNIST
437.9896 nm100Cl Iemission3s2.3p4.(3P).4s 4P → 3s2.3p4.(3P).5p 4D*MeasuredNIST
438.9751 nm100Cl Iemission3s2.3p4.(3P).4s 4P → 3s2.3p4.(3P).5p 4D*MeasuredNIST
443.8488 nm100Cl Iemission3s2.3p4.(3P).4s 4P → 3s2.3p4.(3P).5p 4P*MeasuredNIST
452.6182 nm100Cl Iemission3s2.3p4.(3P).4s 2P → 3s2.3p4.(3P).5p 2P*MeasuredNIST
439.0403 nm90Cl Iemission3s2.3p4.(3P).4s 4P → 3s2.3p4.(3P).5p 4D*MeasuredNIST
440.302 nm90Cl Iemission3s2.3p4.(3P).4s 4P → 3s2.3p4.(3P).5p 4P*MeasuredNIST
447.5304 nm90Cl Iemission3s2.3p4.(3P).4s 4P → 3s2.3p4.(3P).5p 2D*MeasuredNIST
460.0977 nm80Cl Iemission3s2.3p4.(3P).4s 2P → 3s2.3p4.(3P).5p 2P*MeasuredNIST
466.1208 nm80Cl Iemission3s2.3p4.(3P).4s 2P → 3s2.3p4.(3P).5p 2P*MeasuredNIST

Extended Properties

Covalent Radii (Extended)

Covalent radius (Pyykkö)  
Covalent radius (Pyykkö, double)  
Covalent radius (Pyykkö, triple)  
Covalent radius (Bragg)  

Van der Waals Radii

Bondi  
Batsanov  
Alvarez  
UFF  
MM3  
Dreiding  
Rowland–Taylor  

Atomic & Metallic Radii

Atomic radius (Rahm)  
Metallic radius (C12)  

Numbering Scales

Mendeleev
Pettifor
Glawe

Electronegativity Scales

Ghosh
Gunnarsson–Lundqvist
Robles–Bartolotti

Polarizability & Dispersion

Dipole polarizability  
Dipole polarizability (unc.)  
C₆  
C₆ (Gould–Bučko)  

Chemical Affinity

Proton affinity  
Gas basicity  

Supply Risk & Economics

Production concentration
Relative supply risk
Political stability (top producer)

Phase Transitions & Allotropes

Melting point171.65 K
Boiling point239.11 K
Critical point (temperature)417.05 K
Critical point (pressure)7.99 MPa

Oxidation State Categories

+5 main
+4 extended
−1 main
+7 main
+3 main
+6 extended
+1 main
+2 extended

Advanced Reference Data

Screening Constants (5)
nOrbitalσ
1s0.4761
2p4.0068
2s5.5696
3p10.8839
3s9.9317
Crystal Radii Detail (4)
ChargeCNSpinrcrystal (pm)Origin
-1VI167Pauling's (1960) crystal radius,
5IIIPY26
7IV22
7VI41Ahrens (1952) ionic radius,
Isotope Decay Modes (45)
IsotopeModeIntensity
28p100%
29p100%
30p100%
31B+100%
31B+p2.4%
32B+100%
32B+A0.1%
32B+p0%
33B+100%
34B+100%
X‑ray Scattering Factors (504)
Energy (eV)f₁f₂
10—1.46938
10.1617—1.6922
10.3261—1.9488
10.4931—2.24432
10.6628—2.51303
10.8353—2.73153
11.0106—2.95549
11.1886—3.19416
11.3696—3.48881
11.5535—3.87618

Additional Data

Sources

Sources of this element.

In nature it is found in the combined state only, chiefly with sodium as common salt (NaCl), carnallite, and sylvite.

References (1)

Isotopes in Forensic Science and Anthropology

Information on the use of this element's isotopes in forensic science and anthropology.

Analyses of chlorine isotopes and other environmental tracers can help to identify whether an environmental contaminant is of anthropogenic origin or naturally occurring. For example, perchlorate (ClO4 -) can be of anthropogenic origin and is also found naturally. Perchlorate is a widespread groundwater contaminant that can interfere with hormone production in the thyroid gland by displacing iodide. Both the stable chlorine isotope-amount ratio n(37Cl)/n(35Cl) and the mole fraction of 36Cl, n(36Cl)/n(Cl), can provide useful information about origins of perchlorate in the environment (Fig. IUPAC.17.2). Such information may be important for legal reasons and for remediation of contaminated areas [152] [152] M. A. Stewart, A. J. Spivack. Rev. Mineral. Geochem.55, 231 (2004).[152] M. A. Stewart, A. J. Spivack. Rev. Mineral. Geochem.55, 231 (2004).[152] M. A. Stewart, A. J. Spivack. Rev. Mineral. Geochem.55, 231 (2004).[152] M. A. Stewart, A. J. Spivack. Rev. Mineral. Geochem.55, 231 (2004)., [153] [153] J. K. Böhlke, N. C. Sturchio, B. Gu, J. Horita, G. M. Brown, W. A. Jackson, J. R. Batista, P. B. Hatzinger. Anal. Chem.77, 7838 (2005).[153] J. K. Böhlke, N. C. Sturchio, B. Gu, J. Horita, G. M. Brown, W. A. Jackson, J. R. Batista, P. B. Hatzinger. Anal. Chem.77, 7838 (2005)..

References (4)
  • [152] M. A. Stewart, A. J. Spivack. Rev. Mineral. Geochem.55, 231 (2004).
  • [153] J. K. Böhlke, N. C. Sturchio, B. Gu, J. Horita, G. M. Brown, W. A. Jackson, J. R. Batista, P. B. Hatzinger. Anal. Chem.77, 7838 (2005).
  • [154] J. K. Böhlke, P. Hatzinger, N. C. Sturchio, B. Gu, I. J. Abbene, S. J. Mroczkowski. Environ. Sci. Technol.43, 5619 (2009).
  • [4] IUPAC Periodic Table of the Elements and Isotopes (IPTEI) https://doi.org/10.1515/pac-2015-0703

References

(9)
2 Atomic Mass Data Center (AMDC), International Atomic Energy Agency (IAEA)
Cl

The half-life and atomic mass data was provided by the Atomic Mass Data Center at the International Atomic Energy Agency.

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3 IUPAC Commission on Isotopic Abundances and Atomic Weights (CIAAW)
Chlorine

Element data are cited from the Atomic weights of the elements (an IUPAC Technical Report). The IUPAC periodic table of elements can be found at https://iupac.org/what-we-do/periodic-table-of-elements/. Additional information can be found within IUPAC publication doi:10.1515/pac-2015-0703 Copyright © 2020 International Union of Pure and Applied Chemistry.

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4 IUPAC Periodic Table of the Elements and Isotopes (IPTEI)

The information are cited from Pure Appl. Chem. 2018; 90(12): 1833-2092, https://doi.org/10.1515/pac-2015-0703.

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License note: Copyright (c) 2020 International Union of Pure and Applied Chemistry. The International Union of Pure and Applied Chemistry (IUPAC) contribution within Pubchem is provided under a CC-BY-NC-ND 4.0 license, unless otherwise stated.
5 Jefferson Lab, U.S. Department of Energy
Chlorine

Thomas Jefferson National Accelerator Facility (Jefferson Lab) is one of 17 national laboratories funded by the U.S. Department of Energy. The lab's primary mission is to conduct basic research of the atom's nucleus using the lab's unique particle accelerator, known as the Continuous Electron Beam Accelerator Facility (CEBAF). For more information visit https://www.jlab.org/

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License note: Please see citation and linking information: https://education.jlab.org/faq/index.html
6 Los Alamos National Laboratory, U.S. Department of Energy
Chlorine

The periodic table at the LANL (Los Alamos National Laboratory) contains basic element information together with the history, source, properties, use, handling and more. The provenance data may be found from the link under the source name.

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7 NIST Physical Measurement Laboratory
Chlorine

The periodic table contains NIST's critically-evaluated data on atomic properties of the elements. The provenance data that include data for atomic spectroscopy, X-ray and gamma ray, radiation dosimetry, nuclear physics, and condensed matter physics may be found from the link under the source name. Ref: https://www.nist.gov/pml/atomic-spectra-database

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8 PubChem Elements
Chlorine

This section provides all form of data related to element Chlorine.

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9 PubChem Elements
Chlorine

The element property data was retrieved from publications.

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Last updated:

Data verified:

Content is reviewed against latest scientific data.