Bromine
[Ar] 3d¹⁰ 4s² 4p⁵ · 2 · 8 · 18 · 7
The only nonmetal that is liquid at room temperature, and one of just two liquid elements. Bromine's heavy red-brown vapour smells appalling — hence the name, from the Greek for stench.
3D model
Bohr model: nucleus and electron shells from the real configuration. Valence electrons are highlighted.
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Atomic properties
- Atomic number
- 35
- Atomic mass
- 79.904 а.е.м.
- Electron configuration
- [Ar] 3d¹⁰ 4s² 4p⁵
- Electrons per shell
- 2 · 8 · 18 · 7
- Block
- p-block
- Group
- Halogens
- Period
- 4
- Electronegativity (Pauling)
- 2.96
- Electronegativity (Allen)
- 2.69
- Atomic radius
- 94 pm
- Covalent radius
- 120 pm
- Van der Waals radius
- 185 pm
- Ionisation energy 1
- 1 139.9 kJ/mol
- Ionisation energy 2
- 2 103 kJ/mol
- Ionisation energy 3
- 3 470 kJ/mol
- Ionisation energy 4
- 4 560 kJ/mol
- Ionisation energy 5
- 5 760 kJ/mol
- Electron affinity
- 324.6 kJ/mol
- Common oxidation states
- -1, +1, +5
- Oxidation states
- -1, +1, +3, +4, +5, +7
Physical properties
- State at 25 °C
- liquid
- Density
- 3.103 g/cm³
- Melting point
- 265.8 K · -7.3 °C
- Boiling point
- 332 K · 58.9 °C
- Speed of sound
- no data
Thermal properties
- Heat of fusion
- 10.571 kJ/mol
- Heat of vaporisation
- 29.96 kJ/mol
- Specific heat capacity
- 0.474 J/(g·K)
- Thermal conductivity
- 0.122 W/(m·K)
Mechanical properties
- Young's modulus
- no data
- Shear modulus
- no data
- Bulk modulus
- 1.9 GPa
- Poisson ratio
- no data
- Mohs hardness
- no data
- Brinell hardness
- no data
Electrical and magnetic properties
- Electrical resistivity
- 7.8·10¹⁰ nΩ·m
- Magnetic ordering
- diamagnetic
- Curie point
- no data
- Néel point
- no data
- Superconducting point
- no data
Crystal structure
- Crystal structure
- orthorhombic
- Lattice constants
- a = 672.65 pm · b = 464.51 pm · c = 870.23 pm
Abundance
- In the crust
- 2.4 mg/kg
- In the ocean
- 67.3 mg/L
- In the universe
- 0.007 mg/kg
- In the human body
- 2.9 mg/kg
Isotopes
| Isotope | Abundance | Half-life | Decay mode |
|---|---|---|---|
| 79Br | 50.69 % | stable | — |
| 81Br | 49.31 % | stable | — |
Two stable isotopes in near-equal proportion, which gives bromine-containing compounds their characteristic doublet in a mass spectrum.
Discovery
- Year of discovery
- 1826
- Discovered by
- Antoine Jérôme Balard
- Where
- France
- Origin of the name
- from Greek bromos (stench): the vapour smells foul
History
Antoine Balard isolated bromine in 1826 from Mediterranean saltworks brine. Justus Liebig had held the same reagent shortly before but took it for iodine chloride and missed the discovery.
Where it occurs
2.4 mg/kg of the crust, but 67 mg/L of seawater. The industrial sources are Dead Sea brines and subsurface brines in Arkansas.
How it is produced
Chlorine displaces bromine from brine, and air or steam strips it out. The process is simple and has barely changed in a century.
Role in living things
Long thought unnecessary, but in 2014 bromine was shown to be required for cross-linking collagen IV in basement membranes — making it the first new essential trace element in decades.
Safety
Liquid bromine causes severe chemical burns and the vapour attacks the airways. Bromides were widely used as sedatives in the nineteenth century, producing chronic bromism.
Uses
- Brominated flame retardants in plastics, textiles and electronics
- Silver bromide, the light-sensitive layer of classic photographic film
- High-density drilling fluids based on zinc and calcium bromide
- Fumigants and pharmaceutical intermediates
Curiosities
- Bromine and mercury are the only two elements liquid at room temperature and ordinary pressure.
- Tyrian purple of antiquity is dibromoindigo, harvested from sea snails; a gram of dye took ten thousand molluscs.
- That mass-spectrometry doublet gives away the presence of bromine at a glance.
- In the atmosphere bromine destroys ozone about fifty times more efficiently than chlorine.