Bromine Facts (Atomic Number 35 or Br)

Bromine Chemical & Physical Properties

Bromine symbol
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Bromine is a halogen element with atomic number 35 and element symbol Br. At room temperature and pressure, it is one of the few liquid elements. Bromine is known for its brown color and characteristic acrid odor. Here is a collection of facts about the element:

Bromine Atomic Data

Atomic Number: 35

Symbol: Br

Atomic Weight: 79.904

Electron Configuration: [Ar]4s23d104p5

Word Origin: Greek bromos, which means "stench"

Element Classification: Halogen

Discovery: Antoine J. Balard (1826, France)

Density (g/cc): 3.12

Melting Point (°K): 265.9

Boiling Point (°K): 331.9

Appearance: reddish-brown liquid, metallic luster in solid form

Isotopes: There are 29 known isotopes of bromine ranging from Br-69 to Br-97. There are 2 stable isotopes: Br-79 (50.69% abundance) and Br-81 (49.31% abundance).

Atomic Volume (cc/mol): 23.5

Covalent Radius (pm): 114

Ionic Radius: 47 (+5e) 196 (-1e)

Specific Heat (@20°C J/g mol): 0.473 (Br-Br)

Fusion Heat (kJ/mol): 10.57 (Br-Br)

Evaporation Heat (kJ/mol): 29.56 (Br-Br)

Pauling Negativity Number: 2.96

First Ionizing Energy (kJ/mol): 1142.0

Oxidation States: 7, 5, 3, 1, -1

Lattice Structure: Orthorhombic

Lattice Constant (Å): 6.670

Magnetic Ordering: nonmagnetic

Electrical Resistivity (20 °C): 7.8×1010 Ω·m

Thermal Conductivity (300 K): 0.122 W·m−1·K−1

CAS Registry Number: 7726-95-6

Bromine Trivia

  • Bromine is named after the Greek word bromos meaning stench because bromine smells... "stinky." It's a sharp, acrid odor that's hard to describe, but many people know the smell from the element's use in swimming pools.
  • Bromine was nearly discovered by two other chemists before Antoine Jerome Balard published his discovery. The first was in 1825 by the German chemist Justus von Liebig. He was sent a sample of salt water to analyze from a nearby town. He thought the brown liquid he separated from the salt water was a simple mixture of iodine and chlorine. After he learned of Balard's discovery, he went back and checked. His liquid was the newly discovered bromine. The other discoverer was a chemistry student named Carl Loewig. He separated the same brown liquid in 1825 from another sample of salt water. His professor asked him to prepare more of the brown liquid for further testing and soon learned of Balard's bromine.
  • Elemental bromine is a toxic substance and can cause corrosion burns when exposed to skin. Inhalation can cause irritation, in low concentrations, or death, in high concentration.
  • Although toxic as a pure element and in high doses, bromine is an essential element for animals. The bromide ion is a cofactor in collagen synthesis.
  • In World War I, xylyl bromide and related bromine compound were used as poison gas.
  • Compounds containing bromine in the -1 oxidation state are called bromides.
  • Bromine is the tenth most abundant element in sea water with an abundance of 67.3 mg/L.
  • Bromine is the 64th most abundant element in the Earth's crust with an abundance of 2.4 mg/kg.
  • At room temperature, elemental bromine is a reddish-brown liquid. The only other element that is a liquid at room temperature is mercury.
  • Bromine is used in many fire retardant compounds. When brominated compounds burn, hydrobromic acid is produced. The acid acts as a flame retardant by interfering with the oxidation reaction of combustion. Nontoxic halomethane compounds, such as bromochloromethane and bromotrifluoromethane, are used in submarines and spacecraft. However, they are not generally useful because they are expensive and because they damage the ozone layer.
  • Bromide compounds used to be used as sedatives and anticonvulsants. Specifically, sodium bromide and potassium bromide were used in the 19th and 20th century until they were replaced by chloral hydrate, which was in turn replaced by barbituates and other drugs.
  • The ancient royal purple dye called Tyrian Purple is a bromine compound.
  • Bromine was used in leaded fuels to help prevent engine knock in the form of ethylene bromide.
  • Herbert Dow, founder of the Dow Chemical Company started his business separating bromine from brine waters of the Midwestern United States.


  • Duan, Defang; et al. (2007-09-26). "Ab initio studies of solid bromine under high pressure". Physical Review B. 76 (10): 104113. doi:10.1103/PhysRevB.76.104113
  • Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 0-08-037941-9.
  • Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, FL: CRC Press. p. 4.121. ISBN 1439855110.
  • Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.
  • Weeks, Mary Elvira (1932). "The discovery of the elements: XVII. The halogen family". Journal of Chemical Education. 9 (11): 1915. doi:10.1021/ed009p1915

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Helmenstine, Anne Marie, Ph.D. "Bromine Facts (Atomic Number 35 or Br)." ThoughtCo, Feb. 16, 2021, Helmenstine, Anne Marie, Ph.D. (2021, February 16). Bromine Facts (Atomic Number 35 or Br). Retrieved from Helmenstine, Anne Marie, Ph.D. "Bromine Facts (Atomic Number 35 or Br)." ThoughtCo. (accessed June 5, 2023).