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Compare Chlorine vs Bromine

Comparing Chlorine (Cl) and Bromine (Br). Atomic numbers 17 and 35 with atomic masses 35.446 u and 79.901 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
Br
Bromine
#35

Periodic properties of the elements

ChlorineBromine
SymbolClBr
Atomic number1735
Group1717
Period34
Blockpp
Element categoryNonmetalNonmetal

Physical properties

ChlorineBromine
Phase at STPGasLiquid
Density3.2 g/cm33.1028 g/cm3
Atomic weight35.446 u79.901 u
Melting point171.6 K
-101.55 °C
-150.79 °F		265.8 K
-7.35 °C
18.77 °F
Boiling point239.11 K
-34.04 °C
-29.272 °F		332 K
58.85 °C
137.93 °F

Atomic properties

ChlorineBromine
Electronegativity (Pauling Scale)3.162.96
Electron affinity348.575 kJ/mol324.537 kJ/mol
Oxidation states−1, +1, +2, +3, +4, +5, +6, +7
(a strongly acidic oxide)		−1, +1, +3, +4, +5, +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. 1139.9 kJ/mol
  2. 2103 kJ/mol
  3. 3470 kJ/mol
  4. 4560 kJ/mol
  5. 5760 kJ/mol
  6. 8550 kJ/mol
  7. 9940 kJ/mol
  8. 18600 kJ/mol

Electron configuration

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

History

ChlorineBromine
DiscoveryCarl Wilhelm Scheele (1774)Antoine Jérôme Balard, Carl Jacob Löwig (1825)
First isolationCarl Wilhelm Scheele (1774)Antoine Jérôme Balard, Carl Jacob Löwig (1825)
Named bySir Humphry Davy (1810)
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