Bromine Facts – Atomic Number 35 and Element Symbol Br

Bromine Facts
Bromine is element atomic number 35 with symbol Br. It is a reddish brown liquid halogen.

Bromine is atomic number 35 with element symbol Br on the periodic table. It is the only element besides mercury that is a liquid at room temperature and pressure. You encounter bromine in swimming pools and flame retardants. Here is a collection of useful and interesting bromine facts.

Basic Bromine Facts

Bromine is a reddish-brown liquid at room temperature and pressure. (photo: Alchemist-hp)

Name: Bromine

Atomic Number: 35

Element Symbol: Br

Group: Group 17

Period: Period 4

Block: p-block

Element Family: Halogen

Atomic Mass: [79.901, 79.907]; conventional: 79.904

Electron Configuration: [Ar] 3d10 4s2 4p5

Appearance: Reddish-brown liquid

Discovery: Carl Jacob Löwig and Antoine Balard discovered the element bromine in 1825 and 1826, respectively. Although Löwig discovered the element first, Balard published his results first. Löwig isolated the element from a mineral water spring taken from his home town of Bad Kreuznach, Germany. Balard isolated bromine from seaweed ash taken from a salt marsh of Montpellier, France. In 1825, German chemist Justus von Liebig also isolated a brown liquid from a sample of salt water, but he didn’t realize it was a new element until after he learned of Balard’s publication.

Name Origin: Balard named the new element muride, from the Latin word for brine, muria. But, he changed the name to brôme in his publication, from the Greek word for “stench.” The name comes from the acrid smell of bromine vapor. Eventually, the element name changed to bromine to use the -ine halogen name suffix.

Isotopes: Natural bromine consists of two stable isotopes: 79Br and 81Br, with 79Br accounting for 51% of the natural abundance of the element. Numerous radioisotopes have been synthesized. The most stable isotope is 77Br, with a half-life of 57.04 hours.

Abundance: Bromine is the 64th most abundant element in the Earth’s crust with an abundance of 2.4 mg/kg. It is the is the tenth most abundant element in sea water with an abundance of 67.3 mg/L. Commercially, bromine is extracted from bromine pools in Israel, the United States, and China.

Biological Role: Like chlorine, elemental bromine is a toxic substance that causes chemical burns to skin. Inhalation can cause irritation, in low concentrations, or death, in high concentration. However, bromine is an essential element in animals. The bromide ion is a cofactor in collagen synthesis. Bromine also helps white blood cells kill parasites and serves a role in REM sleep. 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 barbiturates and other drugs.

Uses: Bromine is used in many flame 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. Bromine is used to sanitize swimming pools, much like chlorine. Bromine is used to make brominated plastics and polymers. Bromomethane is a pesticide fumigant. 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. Bromine was used in leaded fuels to help prevent engine knock in the form of ethylene bromide.

Bromine Physical Data

Phase at STP: Liquid

Density: Br2 liquid: 3.1028 g/cm3

Melting Point: (Br2) 265.8 K ​(−7.2 °C, ​19 °F)

Boiling Point: (Br2) 332.0 K ​(58.8 °C, ​137.8 °F)

Critical Point: 588 K, 10.34 MPa

Heat of Fusion: (Br2) 10.571 kJ/mol

Heat of Vaporization: (Br2) 29.96 kJ/mol

Molar Heat Capacity: (Br2) 75.69 J/(mol·K)

Atomic Data

Electron Levels of a Bromine Atom
Electron structure of a bromine atom.

Atomic Radius: 120 pm

Covalent Radius: 120±3 pm

Van der Waals Radius: 185 pm

Electronegativity: Pauling scale: 2.96

1st Ionization Energy: 1139.9 kJ/mol

2nd Ionization Energy: 2103 kJ/mol

3rd Ionization Energy: 3470 kJ/mol

Oxidation States: −1+1+3, +4, +5, +7

Crystal Structure: Orthorhombic

Magnetic Ordering: Diamagnetic

Interesting Bromine Facts

  • Bromides are compounds that contain bromine in its -1 oxidation state. Although this is the most common state for bromine and other halogens, it isn’t the only one.
  • Brominated vegetable oil is a food additive that keeps citrus flavoring from separating out of soda. Long-term exposure causes neurological symptoms. Its use is banned in Europe, but not in the United States.
  • The ancient royal purple dye called Tyrian Purple is a bromine compound.
  • Bromothymol blue is a bromine-based pH indicator.
  • The Dow Chemical Company got its start when Herbert Dow separated bromine from brine waters of the Midwestern United States.
  • Xylyl bromide and related bromine compounds were used as poison gas in World War I.


  • 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. ISBN 1439855110.
  • Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. 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