Periodic table › Bromine
1. Identity and classification
Colored, pungent, reactive diatomic nonmetal (gas, volatile liquid, or crystalline solid)
- Name and symbol
- Bromine (Bromine) · Br
- Atomic number
- 35
- Relative atomic weight / mass number
- 79.904 ± 0.003
- Group · period · block
- 17 · 4 · p
- Category
- Halogen
- State near room temperature
- Liquid
- Stable isotopes
- At least one stable isotope
- CAS number
- 7726-95-6
Square brackets [A] indicate a representative isotope mass number, not an average atomic weight. Neutron counts differ between isotopes.
2. Atomic structure and electron configuration
- Protons · electrons in a neutral atom
- 35 · 35
- Neutrons in reference isotope
- 44 (79Br)
- Full electron configuration
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁵- Abbreviated configuration
[Ar]4s² 3d¹⁰ 4p⁵- Electrons per shell
- 2, 8, 18, 7
- Listed oxidation states
- +5, +1, -1
- Electronegativity
- 2.96 (Pauling)
- First ionization energy
- 1139.878 kJ/mol · 11.814 eV
- Electron affinity
- 324.673 kJ/mol
- Covalent radius
- 120 pm
- van der Waals radius
- 183 pm
Configurations of superheavy elements may include theoretical predictions. Different definitions of atomic radius are not interchangeable.
3. Physical and thermal properties
- Density
- 3.11 g/cm³
- Melting point
- 265.95 K · -7.2 °C · 19.04 °F
- Boiling point
- 331.95 K · 58.8 °C · 137.84 °F
- Crystal structure
- Orthorhombic
- Specific heat
- 0.474 J/(g·K)
- Thermal conductivity
- 0.122 W/(m·K)
- Enthalpy of fusion
- 10.57 kJ/mol
- Enthalpy of vaporization
- 29.96 kJ/mol
- Magnetic ordering
- Diamagnetic
- Mohs hardness
- Not established
- Speed of sound
- 206 m/s
Density and structure depend on temperature, pressure and allotrope. 25°C is a room-temperature reference, not STP. Unestablished values are not zero.
4. Chemical behavior and compounds
Bromine is a liquid at room temperature; bromide ions have different properties.
Selected compounds: BrO / Br₂O₃ (Oxide) · BrClₙ (Chloride) · BrFₙ (Fluoride)
Reaction reference
Bromine is an oxidizing halogen.
Bromine dissolves and partially hydrolyzes in water.
5. Isotopes
| Isotope | Status | Natural abundance | Half-life |
|---|---|---|---|
| 79Br | Stable | 50.65% | Stable |
| 80Br | Radioactive | — | 17.68 m |
| 81Br | Stable | 49.35% | Stable |
Half-life units: s seconds, m minutes, h hours, d days, Y years. A dash means no natural-abundance value is given, not zero. Listed records are selected ground states; metastable states are distinct.
6. Discovery and occurrence
- Discovery
- 1826 CE
- Scientists associated with discovery
- Antoine Jérôme Balard & Carl Jacob Löwig
- Location
- France / Germany
- Origin
- Natural
- Listed crustal abundance
- Not established
Minerals and naming reference
Natural brines (Dead Sea, Arkansas, Michigan) and seawater
Named from scientific/historical roots associated with Bromine (Br), discovered or characterized by Antoine Jérôme Balard & Carl Jacob Löwig.
7. Applications
Flame retardants (brominated polymers), drilling completion fluids (CaBr₂/ZnBr₂), silver bromide photographic emulsions, sedatives & intermediates
Detailed applications by field
- everyday
- Flame retardants (brominated polymers), drilling completion fluids (CaBr₂/ZnBr₂), silver bromide photographic emulsions, sedatives & intermediates
- industry
- Used in halogen processing, specialized alloys, and chemical manufacturing (Flame retardants (brominated polymers), drilling completion fluids (CaBr₂/ZnBr₂), silver bromide photographic emulsions, sedatives & intermediates).
- electronics
- Applied in electronic components, semiconductors, or functional coatings where Bromine's electronic structure ([Ar] 3d¹⁰ 4s² 4p⁵) provides target conductivity.
- medicine
- Diagnostic imaging, biomedical instrumentation, or pharmaceutical synthesis research.
- energy
- Utilized in power generation, battery materials, catalysts, or nuclear technology involving Bromine.
- aerospace
- High-performance materials, structural alloys, or space instrumentation utilizing Bromine.
- agriculture
- Soil geochemistry analysis, trace micronutrient research, or analytical environmental monitoring.
- science
- Spectroscopic standard, crystallography, and quantum chemistry studies of Period 4 p-block elements.
8. Biological role and safety
Hazard depends on the isotope, chemical form, dose and exposure route.
Elemental substances, ions, compounds and radioisotopes can have different health effects. This is an educational reference; laboratory work requires the material safety data sheet and trained supervision.
Biological role reference
Classified as trace element in human and biological systems.