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Compare Chlorine vs Iodine

Comparing Chlorine (Cl) and Iodine (I). Atomic numbers 17 and 53 with atomic masses 35.446 u and 126.904 u, classified as nonmetal and nonmetal. Below: a side-by-side comparison of their physical, atomic, electron-configuration and historical properties, including density, melting and boiling points, ionization energies, oxidation states and discovery history.

vs
Cl
Chlorine
#17
I
Iodine
#53

Periodic properties of the elements

ChlorineIodine
SymbolClI
Atomic number1753
Group1717
Period35
Blockpp
Element categoryNonmetalNonmetal

Physical properties

ChlorineIodine
Phase at STPGasSolid
Density3.2 g/cm34.933 g/cm3
Atomic weight35.446 u126.904 u
Melting point171.6 K
-101.55 °C
-150.79 °F		386.85 K
113.7 °C
236.66 °F
Boiling point239.11 K
-34.04 °C
-29.272 °F		457.4 K
184.25 °C
363.65 °F

Atomic properties

ChlorineIodine
Electronegativity (Pauling Scale)3.162.66
Electron affinity348.575 kJ/mol295.153 kJ/mol
Oxidation states−1, +1, +2, +3, +4, +5, +6, +7
(a strongly acidic oxide)		−1, +1, +3, +4, +5, +6, +7
(a strongly acidic oxide)
Ionization energies
  1. 1251.2 kJ/mol
  2. 2298 kJ/mol
  3. 3822 kJ/mol
  4. 5158.6 kJ/mol
  5. 6542 kJ/mol
  6. 9362 kJ/mol
  7. 11018 kJ/mol
  8. 33604 kJ/mol
  9. 38600 kJ/mol
  10. 43961 kJ/mol
  11. 51068 kJ/mol
  12. 57119 kJ/mol
  13. 63363 kJ/mol
  14. 72341 kJ/mol
  15. 78095 kJ/mol
  16. 352994 kJ/mol
  17. 380760 kJ/mol
  1. 1008.4 kJ/mol
  2. 1845.9 kJ/mol
  3. 3180 kJ/mol

Electron configuration

ChlorineIodine
Shorthand configuration[Ne] 3s2 3p5 [Kr] 4d10 5s2 5p5
Full configuration1s2 2s2 2p6 3s2 3p5 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p5
Electrons per shell2, 8, 72, 8, 18, 18, 7

History

ChlorineIodine
DiscoveryCarl Wilhelm Scheele (1774)Bernard Courtois (1811)
First isolationCarl Wilhelm Scheele (1774)Bernard Courtois (1811)
Named bySir Humphry Davy (1810)Joseph Louis Gay-Lussac (1813)
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