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17 Cl Chlorine 35.45

Halogen

Chlorine 氯

[Ne] 3s² 3p⁵

  • Period 3
  • Group 17
  • Block p
  • Gas

Electron configuration

1s² 2s² 2p⁶ 3s² 3p⁵

Orbital diagram (valence)

3s ↑↓
3p ↑↓↑↓↑
Electrons per shell
2, 8, 7
Unpaired electrons
1
Zeff (Slater)
6.10

Properties

Atomic weight
35.45
Electronegativity (Pauling)
3.16
First ionization energy
1251 kJ/mol
Electron affinity
349 kJ/mol
Covalent radius
102 pm
van der Waals radius
175 pm
Melting point
171.7 K
Boiling point
239.1 K
Density
0.003214 g/cm³
Melting / boiling point
−101.5 °C / −34.0 °C
Common oxidation states
+7, +5, +1, −1
Discovered
1774

Natural isotopes

3537m/z020406080100Abundance / %
Mass number AAtomic mass / uAbundance
35Cl34.96885375.76 %
37Cl36.96590324.24 %

Isotope masses: AME2020; abundances: IUPAC/CIAAW representative values.

Successive ionization energies

1: 12.97 eV2: 23.81 eV3: 39.80 eV4: 53.24 eV5: 67.68 eV6: 96.94 eV7: 114.20 eV8: 348.31 eV9: 400.85 eV10: 456.70 eV11: 530.00 eV12: 591.58 eV13: 656.30 eV14: 750.23 eV15: 809.20 eV16: 3658.34 eV17: 3946.29 eV1357911131517n-th electron removed101001000Ionization energy / eV (log)

The big jumps appear where core electrons start to be removed. Ionization energies from the NIST Atomic Spectra Database.

Chlorine in the course

The lessons that discuss this element most (ranked by mentions).

Lab experiments with Chlorine

Standard reduction potentials

HClOX2(aq)+2 HX+(aq)+2 eX−→HClO(aq)+HX2O(l)\ce{HClO2(aq)} + \ce{2H+(aq)} + \ce{2e-} \mathrel{\ce{->}} \ce{HClO(aq)} + \ce{H2O(l)}+1.645 V
2 HClO(aq)+2 HX+(aq)+2 eX−→ClX2(g)+2 HX2O(l)\ce{2HClO(aq)} + \ce{2H+(aq)} + \ce{2e-} \mathrel{\ce{->}} \ce{Cl2(g)} + \ce{2H2O(l)}+1.611 V
ClOX3X−(aq)+6 HX+(aq)+6 eX−→ClX−(aq)+3 HX2O(l)\ce{ClO3-(aq)} + \ce{6H+(aq)} + \ce{6e-} \mathrel{\ce{->}} \ce{Cl-(aq)} + \ce{3H2O(l)}+1.451 V
ClX2(g)+2 eX−→2 ClX−(aq)\ce{Cl2(g)} + \ce{2e-} \mathrel{\ce{->}} \ce{2Cl-(aq)}+1.358 V
ClOX3X−(aq)+3 HX+(aq)+2 eX−→HClOX2(aq)+HX2O(l)\ce{ClO3-(aq)} + \ce{3H+(aq)} + \ce{2e-} \mathrel{\ce{->}} \ce{HClO2(aq)} + \ce{H2O(l)}+1.214 V
ClOX4X−(aq)+2 HX+(aq)+2 eX−→ClOX3X−(aq)+HX2O(l)\ce{ClO4-(aq)} + \ce{2H+(aq)} + \ce{2e-} \mathrel{\ce{->}} \ce{ClO3-(aq)} + \ce{H2O(l)}+1.189 V
ClOX4X−(aq)+HX2O(l)+2 eX−→ClOX3X−(aq)+2 OHX−(aq)\ce{ClO4-(aq)} + \ce{H2O(l)} + \ce{2e-} \mathrel{\ce{->}} \ce{ClO3-(aq)} + \ce{2OH-(aq)}+0.360 V
ClOX3X−(aq)+HX2O(l)+2 eX−→ClOX2X−(aq)+2 OHX−(aq)\ce{ClO3-(aq)} + \ce{H2O(l)} + \ce{2e-} \mathrel{\ce{->}} \ce{ClO2-(aq)} + \ce{2OH-(aq)}+0.330 V
All potentials

Crystal structures

  • NaCl\ce{NaCl} Rock salt (NaCl type) lattice parameter a = 564.0 pm
  • KCl\ce{KCl} Rock salt (NaCl type) lattice parameter a = 629.3 pm
  • CsCl\ce{CsCl} Caesium chloride type lattice parameter a = 412.3 pm
View in the crystal atlas

Periodic trend

H: 1312 kJ/molHe: 2372 kJ/molLi: 520.2 kJ/molBe: 899.5 kJ/molB: 800.6 kJ/molC: 1086 kJ/molN: 1402 kJ/molO: 1314 kJ/molF: 1681 kJ/molNe: 2081 kJ/molNa: 495.8 kJ/molMg: 737.7 kJ/molAl: 577.6 kJ/molSi: 786.5 kJ/molP: 1012 kJ/molS: 999.6 kJ/molCl: 1251 kJ/molAr: 1521 kJ/molK: 418.8 kJ/molCa: 589.8 kJ/molSc: 633 kJ/molTi: 658.8 kJ/molV: 650.9 kJ/molCr: 652.9 kJ/molMn: 717.3 kJ/molFe: 762.4 kJ/molCo: 760.4 kJ/molNi: 737.1 kJ/molCu: 745.4 kJ/molZn: 906.4 kJ/molGa: 578.8 kJ/molGe: 762.2 kJ/molAs: 947 kJ/molSe: 940.9 kJ/molBr: 1140 kJ/molKr: 1351 kJ/molRb: 403 kJ/molSr: 549.5 kJ/molY: 599.8 kJ/molZr: 640.1 kJ/molNb: 652.1 kJ/molMo: 684.3 kJ/molTc: 702.4 kJ/molRu: 710.2 kJ/molRh: 719.7 kJ/molPd: 804.4 kJ/molAg: 731 kJ/molCd: 867.8 kJ/molIn: 558.3 kJ/molSn: 708.6 kJ/molSb: 833.6 kJ/molTe: 869.3 kJ/molI: 1008 kJ/molXe: 1170 kJ/molCs: 375.7 kJ/molBa: 502.9 kJ/mol 0510152025303540455055Atomic number Z05001000150020002500First ionization energy / kJ/mol

Group 17

Data: PubChem periodic table (public domain); atomic weights are IUPAC abridged standard values; covalent radii from Cordero et al. (2008).