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Bromine
Pronunciation/ˈbrmn, -mɪn, -mn/ (BROH-meen, -⁠min, -⁠myn)
Appearancereddish-brown
Standard atomic weight Ar, std(Br)[79.90179.907] conventional: 79.904
Atomic number (Z)35
Groupgroup 17 (halogens)
Periodperiod 4
Blockp-block
Element category  Reactive nonmetal
Electron configuration[Ar] 3d10 4s2 4p5
Electrons per shell
2, 8, 18, 7
Phase at STPliquid
Melting point(Br2) 265.8 K ​(−7.2 °C, ​19 °F)
Boiling point(Br2) 332.0 K ​(58.8 °C, ​137.8 °F)
Density (near r.t.)Br2, liquid: 3.1028 g/cm3
Triple point265.90 K, ​5.8 kPa
Critical point588 K, 10.34 MPa
Heat of fusion(Br2) 10.571 kJ/mol
Heat of vaporisation(Br2) 29.96 kJ/mol
Molar heat capacity(Br2) 75.69 J/(mol·K)
Oxidation states−1, +1, +3, +4, +5, +7 (a strongly acidic oxide)
ElectronegativityPauling scale: 2.96
Ionisation energies
  • 1st: 1139.9 kJ/mol
  • 2nd: 2103 kJ/mol
  • 3rd: 3470 kJ/mol
Atomic radiusempirical: 120 pm
Covalent radius120±3 pm
Van der Waals radius185 pm
Natural occurrenceprimordial
Speed of sound206 m/s (at 20 °C)
Thermal conductivity0.122 W/(m·K)
Electrical resistivity7.8×1010 Ω·m (at 20 °C)
Magnetic orderingdiamagnetic
Magnetic susceptibility−56.4·10−6 cm3/mol
CAS Number7726-95-6
Discovery and first isolationAntoine Jérôme Balard and Carl Jacob Löwig (1825)