Bromine
Atomic Data
| Atomic Number | 35 |
| Symbol | Br |
| Atomic Weight | 79.904 u |
| Density (STP) | 3.1028 g/cm³ |
| Melting Point | −7.3 °C (265.85 K) |
| Boiling Point | 58.85 °C (332.0 K) |
| Electronegativity | 2.96 (Pauling) |
| Electron Config. | 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p5 |
| Oxidation States | −1, +1, +3, +5 |
| Phase at STP | Liquid |
| Category | Halogen |
| Period / Group | 4 / 17 |
| CAS Number | 7726-95-6 |
Electron Configuration
[Ar] 3d10 4s2 4p5
| Shell | n | Subshell | Electrons | Cumulative |
|---|---|---|---|---|
| K | 1 | 1s | 2 | 2 |
| L | 2 | 2s | 2 | 4 |
| L | 2 | 2p | 6 | 10 |
| M | 3 | 3s | 2 | 12 |
| M | 3 | 3p | 6 | 18 |
| M | 3 | 3d | 10 | 28 |
| N | 4 | 4s | 2 | 30 |
| N | 4 | 4p | 5 | 35 |
| Total | 35 | 35 | ||
Isotopes of Bromine
Bromine has two naturally occurring stable isotopes. The most abundant is ⁷⁹Br, comprising 50.69% of all naturally occurring Bromine.
| Isotope | Symbol | Protons | Neutrons | Abundance | Stability |
|---|---|---|---|---|---|
| Bromine-79 | ⁷⁹Br | 35 | 44 | 50.69 | Stable |
| Bromine-81 | ⁸¹Br | 35 | 46 | 49.31 | Stable |
Abundance & Occurrence
Bromine is present in Earth's crust at approximately 2.4 ppm by mass and at approximately 7 ppm by mass throughout the universe.
Earth's Crust (ppm by mass)
Universe (ppm by mass)
Discovery & History
Read more about the discovery of the periodic table of elements →
Safety & Handling
- Bromine vapour toxicity: Bromine is a corrosive, volatile red-brown liquid with a pungent odour; vapour concentrations above 1 ppm are immediately irritating to the eyes, nose, and respiratory tract; above 10 ppm the vapour is severely toxic.
- Skin and eye burns: Liquid bromine causes severe chemical burns on contact: it penetrates skin rapidly and produces wounds that are slow to heal; rinse with copious water and seek immediate medical attention.
- Pulmonary hazard: High concentrations of bromine vapour cause chemical pneumonia and pulmonary oedema; always handle bromine in a fume hood with emergency eye wash and drench shower immediately accessible.
- Reactivity: Bromine reacts vigorously with many organic materials, metals, and reducing agents; it is a strong oxidiser and must be stored away from flammable materials and aluminium.
- Transport and storage: Bromine is transported in glass or lead-lined containers; leaking or damaged containers must be managed as a hazmat incident: evacuation and specialist response may be required.
Bromine in the Real World
Real-World Uses
- Flame retardants: Brominated flame retardants (BFRs) such as TBBPA and decabromodiphenyl ether are incorporated into printed circuit boards, television housings, furniture foam, and textiles to slow ignition and fire spread.
- Water disinfection: Bromine tablets (BCDMH) are used to disinfect swimming pools, hot tubs, and cooling tower water; bromine is more stable than chlorine at higher pH and temperature, making it preferred in spa and industrial water treatment.
- Pharmaceutical synthesis: Bromine is used in the synthesis of many drugs; organobromine compounds serve as intermediates in pharmaceutical manufacturing, and lithium bromide is used as a sedative and anti-epileptic.
- Photography: Silver bromide (AgBr) is the primary light-sensitive compound in traditional photographic film and paper; its sensitivity to light allows the recording of photographic images through exposure and chemical development.
- Soil fumigation: Methyl bromide (now largely phased out under the Montreal Protocol) was widely used as a broad-spectrum fumigant to control soil pests, nematodes, and pathogens in agriculture before planting.
Downloadable Resources
Free periodic table reference sheets for classrooms, study sessions, and laboratory use.
Frequently Asked Questions
What is bromine used for?
Bromine's largest use today is in flame retardants added to plastics, textiles, and electronics to slow the spread of fire. It is also used in the oil and gas industry for dense drilling fluids, in water treatment (as an alternative to chlorine for pool and hot-tub disinfection), and in the synthesis of pharmaceuticals and agricultural chemicals. Historically, bromides were widely used as sedatives and anticonvulsants.
Is bromine dangerous?
Bromine is a corrosive and toxic substance. The liquid burns skin on contact, and bromine vapour irritates the eyes and respiratory system severely. Inhalation of significant quantities can cause pulmonary oedema and be life-threatening. Bromine is one of only two elements that is liquid at room temperature under standard conditions (mercury is the other), which contributes to its hazardous handling properties.
How was bromine discovered?
Bromine was discovered independently in 1825–1826 by French chemist Antoine Jérôme Balard and German chemist Carl Jacob Löwig. Balard isolated it from the bittern remaining after salt crystallisation from Mediterranean salt marshes and recognised it as a new element. The name comes from the Greek 'bromos', meaning stench: an apt description of the element's pungent, suffocating odour.
Why are bromine flame retardants controversial?
Brominated flame retardants (BFRs) are effective at reducing flammability but several classes: particularly polybrominated diphenyl ethers (PBDEs): have been found to be persistent organic pollutants that bioaccumulate in wildlife and human tissue. Some are suspected endocrine disruptors. Many PBDEs are now banned or restricted under the Stockholm Convention, driving the industry toward alternative flame-retardant chemistries.