Bromine (Br)
Bromine (symbol Br) is the chemical element with atomic number 35: a halogen, liquid at 0 °C, with an atomic mass of 79.904 u. Discovered in 1826 (Antoine-Jérôme Balard).
Bromine is, along with mercury, the only element that is liquid under ordinary conditions. This dark red liquid gives off choking fumes, hence its name from the Greek bromos, “stench.” Extracted from the Dead Sea and other brines, it is used mainly to make flame retardants.
Key facts
- Atomic number
- 35
- Symbol
- Br
- French name
- Brome
- Atomic mass
- 79.904 u
- Molar mass
- 79.904 g/mol
- Family
- Halogens
- Position
- period 4, group 17, p-block
- State at 0 °C
- Liquid
- Melting point
- -7.3 °C
- Boiling point
- 58.9 °C
- Density
- 3.1 g/cm³
- Electronegativity (Pauling)
- 2.96
- First ionization energy
- 1,140 kJ/mol
- Atomic radius
- 115 pm
- Electron configuration
- [Ar] 3d¹⁰ 4s² 4p⁵
- Abundance in Earth's crust
- 2.4 ppm (50th most abundant element)
- Indicative price
- 4 $/kg (order of magnitude)
- Radioactive
- no
- Discovery
- 1826, Antoine-Jérôme Balard
Origin of the name
From the Greek brōmos, stench.
What does bromine look like?
A heavy, dark reddish-brown liquid, nearly three times denser than water, that evaporates easily into orange fumes with an acrid smell.
Where is bromine found?
It is never found pure in nature, only as dissolved bromides. Seawater contains about 65 mg per liter, and the Dead Sea nearly 5 g per liter, making it the world's main source.
Natural sources
- Seawater (bromides)
- Dead Sea brines
- Bromargyrite
- Carnallite (traces)
How is bromine produced?
Chlorine is bubbled through bromide-rich brines: the chlorine “drives out” the bromine, which is collected as a vapor. World output exceeds 400,000 tonnes a year.
Top producers
- Israel
- Jordan
- China
- United States
What is bromine used for?
- Flame retardants for plastics and textiles.
- Oil-drilling fluids (calcium bromide).
- Pool and hot tub water treatment.
- Synthesis of drugs and pesticides.
- Film photography (silver bromide).
In everyday life
- Plastic computer or TV casing (fire-retardant)
- Hot tub sanitizer tablets
- Photographic film
Role in living things
Long thought useless, bromine turned out in 2014 to be essential for building collagen IV, a structural protein of animal tissues. In the 19th century, potassium bromide was the first effective drug against epilepsy and served as a sedative.
Hazards of bromine
Liquid bromine causes severe skin burns, and its fumes violently irritate the eyes and lungs. Some bromine compounds (methyl bromide, halons) destroy the ozone layer and were banned under the Montreal Protocol.
Cosmic origin
- Supernovae: Forged in the cores of massive stars, then scattered when they explode.
- Neutron stars: Created when two neutron stars collide — the “forge” of gold.
History of bromine
In 1826, Antoine-Jérôme Balard, a young pharmacist in Montpellier, France, isolated bromine from the leftover brine of salt marshes. The German Carl Löwig had obtained it shortly before but published too late. The famous chemist Justus von Liebig, for his part, had held a flask of bromine a few years earlier and mistakenly labeled it “iodine chloride.”
Did you know?
- Tyrian purple, the dye of Roman emperors made from sea snails, is a bromine-containing molecule.
- Liebig is said to have kept the mislabeled flask in a cabinet he called his “cupboard of mistakes.”
- Dibromoethane was added to leaded gasoline to flush the lead out of the engine.
Isotopes of bromine
Two stable isotopes in almost equal shares, bromine-79 and bromine-81, hence an atomic mass close to 80.
- bromine-77: radioactive, half-life 2.38 days
- bromine-79: 50.69% of natural bromine, stable
- bromine-81: 49.31% of natural bromine, stable
- bromine-82: radioactive, half-life 1.47 days. Tracer for following water flows and finding leaks.
Related elements
Same family (halogens): Fluorine (F), Chlorine (Cl), Iodine (I), Astatine (At).
Same column (group 17): Fluorine (F), Chlorine (Cl), Iodine (I), Astatine (At), Tennessine (Ts).