Chlorine

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 Number17
Atomic Weight35.45
Mass Number35
Group17
Period3
Blockp
Protons17 p+
Neutrons18 n0
Electrons17 e-
Chlorine liquid in an ampoule.jpg Animated Bohr Model of Cl (Chlorine) Enhanced Bohr Model of Cl (Chlorine) Bohr Model: Cl (Chlorine) Orbital Diagram of Cl (Chlorine)

Properties

Atomic Radius
100 pm
Molar Volume
Covalent Radius
99 pm
Metallic Radius
Ionic Radius
181 pm
Crystal Radius
167 pm
Van der Waals Radius
175 pm
Density
0.002898 g/cm³
Energy
Proton Affinity
513.6 kJ/mol
Electron Affinity
3.612725 eV/particle
Ionization Energy
12.96763 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 Shells2, 8, 7
Valence Electrons5
Electron Configuration[Ne] 3s2 3p5
Oxidation States-1, 1, 2, 3, 4, 5, 6, 7
Electronegativity
3.16
Electrophilicity
3.673315922583194 eV/particle
Phases
PhaseGas
Gas PhaseDiatomic
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
Appearancepale 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
TypeInsulator
Electrical Conductivity
0.00000001 MS/m
Electrical Resistivity
100 m Ω
Superconducting Point
Magnetism
Typediamagnetic
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 StructureBase Centered Orthorhombic (ORC)
Lattice Constant
6.24 Å
Lattice Anglesπ/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
CategoryHalogens, Halogens
CAS GroupVIIB
IUPAC GroupVIIA
Glawe Number101
Mendeleev Number107
Pettifor Number99
Geochemical Classsemi-volatile
Goldschmidt Classlitophile
Other
Gas Basicity
490.1 kJ/mol
Dipole Polarizability
14.6 ± 0.1 a₀
C6 Dispersion Coefficient
94.6 a₀
AllotropesDichlorine
Neutron Cross Section
35.3
Neutron Mass Absorption
0.033
Quantum Numbers2P3/2
Space Group64 (Cmca)

Isotopes of Chlorine

Stable Isotopes2
Unstable Isotopes23
Radioactive Isotopes21

28Cl

Abundance
Relative Atomic Mass
28.030349 ± 0.000537 Da
Mass Number28
G-Factor
Half Life
Spin1
Quadrupole Moment
Discovery Year2018
Parity+

28Cl Decay Modes
Decay ModeIntensity
p (proton emission)100%

29Cl

AbundanceRadioactive ☢️
Relative Atomic Mass
29.015053 ± 0.000203 Da
Mass Number29
G-Factor
Half Life
5.4 ± 1.9 zs
Spin1/2
Quadrupole Moment
0
Discovery Year1993
Parity+

29Cl Decay Modes
Decay ModeIntensity
p (proton emission)100%

30Cl

Abundance
Relative Atomic Mass
30.005018333 ± 0.000025631 Da
Mass Number30
G-Factor
Half Life
Spin3
Quadrupole Moment
Discovery Year2018
Parity+

30Cl Decay Modes
Decay ModeIntensity
p (proton emission)100%

31Cl

AbundanceRadioactive ☢️
Relative Atomic Mass
30.992448097 ± 0.0000037 Da
Mass Number31
G-Factor
Half Life
190 ± 1 ms
Spin3/2
Quadrupole Moment
Discovery Year1977
Parity+

31Cl Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%
β+ p (β+-delayed proton emission)2.4%

32Cl

AbundanceRadioactive ☢️
Relative Atomic Mass
31.985684605 ± 0.000000603 Da
Mass Number32
G-Factor
1.115 ± 0.006
Half Life
298 ± 1 ms
Spin1
Quadrupole Moment
Discovery Year1953
Parity+

32Cl Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%
β+α (β+-delayed α emission)0.054%
β+ p (β+-delayed proton emission)0.026%

33Cl

AbundanceRadioactive ☢️
Relative Atomic Mass
32.977451988 ± 0.000000419 Da
Mass Number33
G-Factor
0.50313333333333 ± 0.0002
Half Life
2.5038 ± 0.0022 s
Spin3/2
Quadrupole Moment
Discovery Year1940
Parity+

33Cl Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%

34Cl

AbundanceRadioactive ☢️
Relative Atomic Mass
33.97376249 ± 0.000000052 Da
Mass Number34
G-Factor
0
Half Life
1.5267 ± 0.0004 s
Spin0
Quadrupole Moment
0
Discovery Year1934
Parity+

34Cl Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%

35Cl

Abundance
75.8 ± 0.2
Relative Atomic Mass
34.968852694 ± 0.000000038 Da
Mass Number35
G-Factor
0.5478 ± 0.000013333333333333
Half Life
Spin3/2
Quadrupole Moment
-0.0817 ± 0.0008
Discovery Year1919
Parity+

36Cl

AbundanceRadioactive ☢️
Relative Atomic Mass
35.968306822 ± 0.000000038 Da
Mass Number36
G-Factor
Half Life
301.3 ± 1.5 ky
Spin2
Quadrupole Moment
-0.178 ± 0.004
Discovery Year1941
Parity+

36Cl Decay Modes
Decay ModeIntensity
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 Number37
G-Factor
0.456 ± 0.0000066666666666667
Half Life
Spin3/2
Quadrupole Moment
-0.0644 ± 0.0006
Discovery Year1919
Parity+

38Cl

AbundanceRadioactive ☢️
Relative Atomic Mass
37.968010408 ± 0.000000105 Da
Mass Number38
G-Factor
1.025 ± 0.01
Half Life
37.23 ± 0.014 m
Spin2
Quadrupole Moment
Discovery Year1940
Parity-

38Cl Decay Modes
Decay ModeIntensity
β (β decay)100%

39Cl

AbundanceRadioactive ☢️
Relative Atomic Mass
38.968008151 ± 0.000001859 Da
Mass Number39
G-Factor
Half Life
56.2 ± 0.6 m
Spin3/2
Quadrupole Moment
Discovery Year1949
Parity+

39Cl Decay Modes
Decay ModeIntensity
β (β decay)100%

40Cl

AbundanceRadioactive ☢️
Relative Atomic Mass
39.970415466 ± 0.000034423 Da
Mass Number40
G-Factor
Half Life
1.35 ± 0.03 m
Spin2
Quadrupole Moment
Discovery Year1956
Parity-

40Cl Decay Modes
Decay ModeIntensity
β (β decay)100%

41Cl

AbundanceRadioactive ☢️
Relative Atomic Mass
40.970684525 ± 0.000073777 Da
Mass Number41
G-Factor
Half Life
38.4 ± 0.8 s
Spin1/2
Quadrupole Moment
0
Discovery Year1971
Parity+

41Cl Decay Modes
Decay ModeIntensity
β (β decay)100%

42Cl

AbundanceRadioactive ☢️
Relative Atomic Mass
41.973342 ± 0.000064 Da
Mass Number42
G-Factor
Half Life
6.8 ± 0.3 s
Spin2
Quadrupole Moment
Discovery Year1971
Parity-

42Cl Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)%

43Cl

AbundanceRadioactive ☢️
Relative Atomic Mass
42.9740637 ± 0.000066407 Da
Mass Number43
G-Factor
Half Life
3.13 ± 0.09 s
Spin3/2
Quadrupole Moment
Discovery Year1976
Parity+

43Cl Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)%

44Cl

AbundanceRadioactive ☢️
Relative Atomic Mass
43.978014918 ± 0.000091859 Da
Mass Number44
G-Factor
0.2749 ± 0.0002
Half Life
562 ± 106 ms
Spin2
Quadrupole Moment
Discovery Year1979
Parity-

44Cl Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)8%

45Cl

AbundanceRadioactive ☢️
Relative Atomic Mass
44.980394353 ± 0.000146177 Da
Mass Number45
G-Factor
Half Life
413 ± 25 ms
Spin3/2
Quadrupole Moment
Discovery Year1979
Parity+

45Cl Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)24%

46Cl

AbundanceRadioactive ☢️
Relative Atomic Mass
45.985254926 ± 0.0001044 Da
Mass Number46
G-Factor
Half Life
232 ± 2 ms
Spin2
Quadrupole Moment
Discovery Year1989
Parity-

46Cl Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)60%
2n (2-neutron emission)%

47Cl

AbundanceRadioactive ☢️
Relative Atomic Mass
46.989715 ± 0.000215 Da
Mass Number47
G-Factor
Half Life
101 ± 5 ms
Spin3/2
Quadrupole Moment
Discovery Year1989
Parity+

47Cl Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)3%
2n (2-neutron emission)%

48Cl

AbundanceRadioactive ☢️
Relative Atomic Mass
47.995405 ± 0.000537 Da
Mass Number48
G-Factor
Half Life
Spin
Quadrupole Moment
Discovery Year1989
Parity

48Cl Decay Modes
Decay ModeIntensity
β (β decay)%
β n (β-delayed neutron emission)%
2n (2-neutron emission)%

49Cl

AbundanceRadioactive ☢️
Relative Atomic Mass
49.000794 ± 0.000429 Da
Mass Number49
G-Factor
Half Life
Spin3/2
Quadrupole Moment
Discovery Year1989
Parity+

49Cl Decay Modes
Decay ModeIntensity
β (β decay)%
β n (β-delayed neutron emission)%
2n (2-neutron emission)%

50Cl

AbundanceRadioactive ☢️
Relative Atomic Mass
50.008266 ± 0.000429 Da
Mass Number50
G-Factor
Half Life
Spin
Quadrupole Moment
Discovery Year2009
Parity

50Cl Decay Modes
Decay ModeIntensity
β (β decay)%
β n (β-delayed neutron emission)%
2n (2-neutron emission)%

51Cl

AbundanceRadioactive ☢️
Relative Atomic Mass
51.015341 ± 0.000751 Da
Mass Number51
G-Factor
Half Life
Spin3/2
Quadrupole Moment
Discovery Year1990
Parity+

51Cl Decay Modes
Decay ModeIntensity
β (β decay)%
β n (β-delayed neutron emission)%
2n (2-neutron emission)%

52Cl

AbundanceRadioactive ☢️
Relative Atomic Mass
52.024004 ± 0.000751 Da
Mass Number52
G-Factor
Half Life
Spin
Quadrupole Moment
Discovery Year2018
Parity

52Cl Decay Modes
Decay ModeIntensity
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

DiscoverersCarl Wilhelm Scheele
Discovery LocationSweden
Discovery Year1774
Etymology (Name Origin)Greek: chlôros (greenish yellow).
PronunciationKLOR-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

1s0.4761
2p4.0068
2s5.5696
3p10.8839
3s9.9317