Chlorine (Cl)

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.

Atomic Number	17
Atomic Weight	35.45
Mass Number	35

Group	17
Period	3
Block	p

Protons	17 p⁺
Neutrons	18 n⁰
Electrons	17 e^-

Properties

Energy
Atomic Radius	100 pm 206 pm
Molar Volume	18.7 cm³/mol
Covalent Radius	99 pm 95 pm 93 pm 105 pm 102 pm
Metallic Radius	91 pm
Ionic Radius	181 pm 12 pm 8 pm 27 pm
Crystal Radius	167 pm 26 pm 22 pm 41 pm
Van der Waals Radius	180 pm 175 pm 395.03 pm 175 pm 207 pm 176 pm 394.7 pm
Density	0.002898 g/cm³
Proton Affinity	513.6 kJ/mol
Electron Affinity	3.612725 eV/particle
Ionization Energy	12.96763 eV/particle 23.81364 eV/particle 39.8 eV/particle 53.24 eV/particle 67.68 eV/particle 96.94 eV/particle 114.2013 eV/particle 348.306 eV/particle 400.851 eV/particle 456.68 eV/particle 529.97 eV/particle 591.58 eV/particle 656.3 eV/particle 750.2 eV/particle 809.198 eV/particle 3,658.34362 eV/particle 3,946.2908 eV/particle

Heat of Vaporization	20.41 kJ/mol
Heat of Fusion	6.41 kJ/mol
Heat of Formation	121.302 kJ/mol
Electrons
Electron Shells	2, 8, 7

Valence Electrons	7

Electron Configuration	[Ne] 3s² 3p⁵

Oxidation States	-1, 1, 2, 3, 4, 5, 6, 7
Electronegativity	16.97 eV/particle 0.263803 3.16
Electrophilicity	3.673315922583194 eV/particle
Phases
Phase	Gas
Gas Phase	Diatomic
Boiling Point	239.11 K
Melting Point	171.65 K
Critical Pressure	7.991 MPa
Critical Temperature	417.05 K
Triple Point
Visual
Color	Yellow #00ff00 #1ff01f #38b538
Appearance	pale yellow-green gas
Refractive Index	1.000773
Thermodynamic Properties
Thermal Conductivity	0.009 W/(m K)
Thermal Expansion
Molar Heat Capacity	33.949 J/(mol K)
Specific Heat Capacity	0.479 J/(g⋅K)
Heat Capacity Ratio (Adiabatic Index)	7/5
Electrical Properties
Type	Insulator
Electrical Conductivity	0.00000001 MS/m
Electrical Resistivity	100 m Ω
Superconducting Point
Magnetism
Type	diamagnetic
Magnetic Susceptibility (Mass)	-0.0000000072 m³/Kg
Magnetic Susceptibility (Molar)	-0.000000000511 m³/mol
Magnetic Susceptibility (Volume)	-0.0000000231
Magnetic Ordering
Curie Point
Neel Point
Structure
Crystal Structure	Base Centered Orthorhombic (ORC)
Lattice Constant	6.24 Å
Lattice Angles	π/2, π/2, π/2
Mechanical Properties
Hardness
Bulk Modulus	1.1 GPa
Shear Modulus
Young Modulus
Poisson Ratio
Speed of Sound	206 m/s
Classification
Category	Halogens, Halogens
CAS Group	VIIB
IUPAC Group	VIIA
Glawe Number	101
Mendeleev Number	107
Pettifor Number	99
Geochemical Class	semi-volatile
Goldschmidt Class	litophile
Other
Gas Basicity	490.1 kJ/mol
Dipole Polarizability	14.6 ± 0.1 a₀
C6 Dispersion Coefficient	94.6 a₀ 97.1 a₀
Allotropes	Dichlorine
Neutron Cross Section	35.3
Neutron Mass Absorption	0.033
Quantum Numbers	2P3/2
Space Group	64 (Cmca)

Isotopes of Chlorine

Stable Isotopes	2
Unstable Isotopes	23
Radioactive Isotopes	21

²⁸Cl

Abundance
Relative Atomic Mass	28.030349 ± 0.000537 Da
Mass Number	28
G-Factor
Half Life
Spin	1
Quadrupole Moment
Discovery Year	2018
Parity	+

²⁸Cl Decay Modes

Decay Mode	Intensity
p (proton emission)	100%

²⁹Cl

Abundance	Radioactive ☢️
Relative Atomic Mass	29.015053 ± 0.000203 Da
Mass Number	29
G-Factor
Half Life	5.4 ± 1.9 zs
Spin	1/2
Quadrupole Moment	0
Discovery Year	1993
Parity	+

²⁹Cl Decay Modes

Decay Mode	Intensity
p (proton emission)	100%

³⁰Cl

Abundance
Relative Atomic Mass	30.005018333 ± 0.000025631 Da
Mass Number	30
G-Factor
Half Life
Spin	3
Quadrupole Moment
Discovery Year	2018
Parity	+

³⁰Cl Decay Modes

Decay Mode	Intensity
p (proton emission)	100%

³¹Cl

Abundance	Radioactive ☢️
Relative Atomic Mass	30.992448097 ± 0.0000037 Da
Mass Number	31
G-Factor
Half Life	190 ± 1 ms
Spin	3/2
Quadrupole Moment
Discovery Year	1977
Parity	+

³¹Cl Decay Modes

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%
β⁺ p (β⁺-delayed proton emission)	2.4%

³²Cl

Abundance	Radioactive ☢️
Relative Atomic Mass	31.985684605 ± 0.000000603 Da
Mass Number	32
G-Factor	1.115 ± 0.006
Half Life	298 ± 1 ms
Spin	1
Quadrupole Moment
Discovery Year	1953
Parity	+

³²Cl Decay Modes

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%
β⁺α (β⁺-delayed α emission)	0.054%
β⁺ p (β⁺-delayed proton emission)	0.026%

³³Cl

Abundance	Radioactive ☢️
Relative Atomic Mass	32.977451988 ± 0.000000419 Da
Mass Number	33
G-Factor	0.50313333333333 ± 0.0002
Half Life	2.5038 ± 0.0022 s
Spin	3/2
Quadrupole Moment
Discovery Year	1940
Parity	+

³³Cl Decay Modes

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%

³⁴Cl

Abundance	Radioactive ☢️
Relative Atomic Mass	33.97376249 ± 0.000000052 Da
Mass Number	34
G-Factor	0
Half Life	1.5267 ± 0.0004 s
Spin	0
Quadrupole Moment	0
Discovery Year	1934
Parity	+

³⁴Cl Decay Modes

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%

³⁵Cl

Abundance	75.8 ± 0.2
Relative Atomic Mass	34.968852694 ± 0.000000038 Da
Mass Number	35
G-Factor	0.5478 ± 0.000013333333333333
Half Life
Spin	3/2
Quadrupole Moment	-0.0817 ± 0.0008
Discovery Year	1919
Parity	+

³⁶Cl

Abundance	Radioactive ☢️
Relative Atomic Mass	35.968306822 ± 0.000000038 Da
Mass Number	36
G-Factor
Half Life	301.3 ± 1.5 ky
Spin	2
Quadrupole Moment	-0.178 ± 0.004
Discovery Year	1941
Parity	+

³⁶Cl Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	98.1%
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	1.9%

³⁷Cl

Abundance	24.2 ± 0.2
Relative Atomic Mass	36.965902573 ± 0.000000055 Da
Mass Number	37
G-Factor	0.456 ± 0.0000066666666666667
Half Life
Spin	3/2
Quadrupole Moment	-0.0644 ± 0.0006
Discovery Year	1919
Parity	+

³⁸Cl

Abundance	Radioactive ☢️
Relative Atomic Mass	37.968010408 ± 0.000000105 Da
Mass Number	38
G-Factor	1.025 ± 0.01
Half Life	37.23 ± 0.014 m
Spin	2
Quadrupole Moment
Discovery Year	1940
Parity	-

³⁸Cl Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

³⁹Cl

Abundance	Radioactive ☢️
Relative Atomic Mass	38.968008151 ± 0.000001859 Da
Mass Number	39
G-Factor
Half Life	56.2 ± 0.6 m
Spin	3/2
Quadrupole Moment
Discovery Year	1949
Parity	+

³⁹Cl Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

⁴⁰Cl

Abundance	Radioactive ☢️
Relative Atomic Mass	39.970415466 ± 0.000034423 Da
Mass Number	40
G-Factor
Half Life	1.35 ± 0.03 m
Spin	2
Quadrupole Moment
Discovery Year	1956
Parity	-

⁴⁰Cl Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

⁴¹Cl

Abundance	Radioactive ☢️
Relative Atomic Mass	40.970684525 ± 0.000073777 Da
Mass Number	41
G-Factor
Half Life	38.4 ± 0.8 s
Spin	1/2
Quadrupole Moment	0
Discovery Year	1971
Parity	+

⁴¹Cl Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

⁴²Cl

Abundance	Radioactive ☢️
Relative Atomic Mass	41.973342 ± 0.000064 Da
Mass Number	42
G-Factor
Half Life	6.8 ± 0.3 s
Spin	2
Quadrupole Moment
Discovery Year	1971
Parity	-

⁴²Cl Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	%

⁴³Cl

Abundance	Radioactive ☢️
Relative Atomic Mass	42.9740637 ± 0.000066407 Da
Mass Number	43
G-Factor
Half Life	3.13 ± 0.09 s
Spin	3/2
Quadrupole Moment
Discovery Year	1976
Parity	+

⁴³Cl Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	%

⁴⁴Cl

Abundance	Radioactive ☢️
Relative Atomic Mass	43.978014918 ± 0.000091859 Da
Mass Number	44
G-Factor	0.2749 ± 0.0002
Half Life	562 ± 106 ms
Spin	2
Quadrupole Moment
Discovery Year	1979
Parity	-

⁴⁴Cl Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	8%

⁴⁵Cl

Abundance	Radioactive ☢️
Relative Atomic Mass	44.980394353 ± 0.000146177 Da
Mass Number	45
G-Factor
Half Life	413 ± 25 ms
Spin	3/2
Quadrupole Moment
Discovery Year	1979
Parity	+

⁴⁵Cl Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	24%

⁴⁶Cl

Abundance	Radioactive ☢️
Relative Atomic Mass	45.985254926 ± 0.0001044 Da
Mass Number	46
G-Factor
Half Life	232 ± 2 ms
Spin	2
Quadrupole Moment
Discovery Year	1989
Parity	-

⁴⁶Cl Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	60%
2n (2-neutron emission)	%

⁴⁷Cl

Abundance	Radioactive ☢️
Relative Atomic Mass	46.989715 ± 0.000215 Da
Mass Number	47
G-Factor
Half Life	101 ± 5 ms
Spin	3/2
Quadrupole Moment
Discovery Year	1989
Parity	+

⁴⁷Cl Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	3%
2n (2-neutron emission)	%

⁴⁸Cl

Abundance	Radioactive ☢️
Relative Atomic Mass	47.995405 ± 0.000537 Da
Mass Number	48
G-Factor
Half Life
Spin
Quadrupole Moment
Discovery Year	1989
Parity

⁴⁸Cl Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	%
β⁻ n (β⁻-delayed neutron emission)	%
2n (2-neutron emission)	%

⁴⁹Cl

Abundance	Radioactive ☢️
Relative Atomic Mass	49.000794 ± 0.000429 Da
Mass Number	49
G-Factor
Half Life
Spin	3/2
Quadrupole Moment
Discovery Year	1989
Parity	+

⁴⁹Cl Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	%
β⁻ n (β⁻-delayed neutron emission)	%
2n (2-neutron emission)	%

⁵⁰Cl

Abundance	Radioactive ☢️
Relative Atomic Mass	50.008266 ± 0.000429 Da
Mass Number	50
G-Factor
Half Life
Spin
Quadrupole Moment
Discovery Year	2009
Parity

⁵⁰Cl Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	%
β⁻ n (β⁻-delayed neutron emission)	%
2n (2-neutron emission)	%

⁵¹Cl

Abundance	Radioactive ☢️
Relative Atomic Mass	51.015341 ± 0.000751 Da
Mass Number	51
G-Factor
Half Life
Spin	3/2
Quadrupole Moment
Discovery Year	1990
Parity	+

⁵¹Cl Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	%
β⁻ n (β⁻-delayed neutron emission)	%
2n (2-neutron emission)	%

⁵²Cl

Abundance	Radioactive ☢️
Relative Atomic Mass	52.024004 ± 0.000751 Da
Mass Number	52
G-Factor
Half Life
Spin
Quadrupole Moment
Discovery Year	2018
Parity

⁵²Cl Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	%
β⁻ n (β⁻-delayed neutron emission)	%
2n (2-neutron emission)	%

History

Around 1630, chlorine was recognized as a gas by the Belgian chemist and physician Jan Baptist van Helmont. Elemental chlorine was first prepared and studied in 1774 by Swedish chemist Carl Wilhelm Scheele. By 1810, the scientific consensus was that chlorine was actually a compound that contained oxygen. In 1811, Sir Humphry Davy concluded the new gas was in fact a new element. From the Greek word chloro, greenish yellow

Discoverers	Carl Wilhelm Scheele
Discovery Location	Sweden
Discovery Year	1774
Etymology (Name Origin)	Greek: chlôros (greenish yellow).
Pronunciation	KLOR-een (English)

Elemental chlorine at high concentrations is extremely dangerous and poisonous

Tree frogs have a chlorine compound in their skin that is a very powerful pain killer

Uses

Chlorine is used for producing safe drinking water. It is also extensively used in the production of paper products, dyestuffs, textiles, petroleum products, medicines, antiseptics, insecticides, food, solvents, paints, plastics, and many other consumer products. Chlorinated compounds are used mostly for sanitation, pulp bleaching, disinfectants, and textile processing. Used in water purification, bleaches, acids and many, many other compounds such as chlorofluorocarbons (CFC).

Sources

Salt (sodium chloride, NaCl) is its most common compound. Commercial quantities are produced by electrolysis of aqueous sodium chloride (seawater or brine from salt mines).

Abundance
Abundance in Earth's crust	145 mg/kg
Abundance in Oceans	19,400 mg/L
Abundance in Human Body	0.12 %
Abundance in Meteor	0.037 %
Abundance in Sun	0.0008 %
Abundance in Universe	0.0001 %

Nuclear Screening Constants

1	s	0.4761
2	p	4.0068
2	s	5.5696
3	p	10.8839
3	s	9.9317

Chlorine on ChemicalAid

Art & Architecture Thesaurus ID	300264246
Australian Educational Vocabulary ID	scot/3509
BNCF Thesaurus ID	792
Bibliothèque nationale de France ID	119811094
Brockhaus Enzyklopädie online ID	chlor-20
CAS Registry Number	7782-50-5
ChEBI ID	23116
Den Store Danske ID	klor
DrugBank ID	11109
EPPO Code	TXCHLO
Encyclopædia Britannica Online ID	science/chlorine
Encyclopædia Universalis ID	chlore
EuroVoc ID	5971
Freebase ID	/m/025tkqp
French Vikidia ID	Chlore
GND ID	4147748-0
Great Russian Encyclopedia Online ID	4694434
KBpedia ID	Chlorine
Latvian National Encyclopedia Online ID	131436
Library of Congress authority ID	sh85024541
MeSH descriptor ID	D002713
NE.se ID	klor
NKCR AUT ID	ph163876
Namuwiki ID	염소(원소)
National Diet Library ID	00562008
National Library of Israel J9U ID	987007285618505171
OmegaWiki Defined Meaning	575
OpenAlex ID	C505241676
OpenAlex ID	C2991844076
OpenAlex ID	C2993530813
PSH ID	5812
Quora topic ID	Chlorine
Römpp online ID	RD-03-01354
STW Thesaurus for Economics ID	18080-0
Spanish Vikidia ID	Cloro
Store medisinske leksikon ID	klor
Store norske leksikon ID	klor
Treccani ID	cloro
UK Parliament thesaurus ID	9150
WordNet 3.1 Synset ID	14658769-n
YSO ID	12904

Chlorine (Cl)

Properties

Isotopes of Chlorine

28Cl

28Cl Decay Modes

29Cl

29Cl Decay Modes

30Cl

30Cl Decay Modes

31Cl

31Cl Decay Modes

32Cl

32Cl Decay Modes

33Cl

33Cl Decay Modes

34Cl

34Cl Decay Modes

35Cl

36Cl

36Cl Decay Modes

37Cl

38Cl

38Cl Decay Modes

39Cl

39Cl Decay Modes

40Cl

40Cl Decay Modes

41Cl

41Cl Decay Modes

42Cl

42Cl Decay Modes

43Cl

43Cl Decay Modes

44Cl

44Cl Decay Modes

45Cl

45Cl Decay Modes

46Cl

46Cl Decay Modes

47Cl

47Cl Decay Modes

48Cl

48Cl Decay Modes

49Cl

49Cl Decay Modes

50Cl

50Cl Decay Modes

51Cl

51Cl Decay Modes

52Cl

52Cl Decay Modes