Bromine: properties, occurrence, uses and safety

Bromine (Br, atomic number 35) is a reddish-brown, diatomic halogen element used in flame retardants, disinfectants and chemical synthesis; it is reactive, corrosive and found mainly in seawater and brines.

Author: Leandro Alegsa Creation date: November 13, 2022 Last updated: May 24, 2026

Overview

Bromine is a chemical element with the symbol Br and atomic number 35. It belongs to the halogen group and is usually encountered as the diatomic molecule Br2. At ordinary temperatures it is one of the few nonmetallic elements that is a liquid, appearing as a dense reddish-brown fluid with a sharp, unpleasant odor. Its approximate atomic mass is 80. For general reference on the element and its place among others, see the element entry at element resources and its group on the halogens page of the periodic table (periodic table).

Physical and chemical characteristics

Bromine is highly reactive and readily forms bromide ions (Br−) in compounds. In common chemistry it behaves as an oxidizer and participates in a range of organic and inorganic reactions. It has several oxidation states, though the −1 state (bromide) is most stable. As a diatomic molecular liquid, it vaporizes to form toxic, reddish vapors and is soluble in organic solvents; many bromine-containing compounds are volatile or reactive.

Occurrence and production

Bromine is widely distributed in the Earth’s oceans and in saline groundwater. It is typically produced industrially by oxidizing bromide-rich brines and then isolating elemental bromine by vaporization and condensation. Sea water contains bromide in low concentration; commercial sources are often natural brine wells, salt lakes or by‑products of other salt production.

Uses and applications

Bromine and bromide compounds have a variety of uses. Important applications include:

Production of organobromine compounds used as flame retardants and plastic additives.
Water treatment and disinfection (bromine-based sanitizers are used in pools and spas).
Chemical synthesis: bromination is a common step in making pharmaceutical and agrochemical intermediates.
Historical and specialty uses: silver bromide in photographic film and certain medicinal bromide salts (now less common).

History, name and notable facts

Bromine was isolated in the early 19th century by several chemists working independently. Its name derives from the Greek word for stench, reflecting the strong odor of the element. As a member of the halogen group it is closely related to chlorine and iodine but has distinct physical properties such as being liquid at near-room temperatures.

Safety and environmental considerations

Elemental bromine and many bromine compounds are toxic and corrosive; vapors can irritate eyes and airways and direct contact causes burns. Some brominated organic chemicals are persistent in the environment and have raised ecological and health concerns, so their manufacture and use are regulated in many countries. Handling bromine requires appropriate protective equipment and engineering controls to avoid exposure.

Discovery

Bromine was extracted from seaweed in the salt marshes near Montpellier in 1826 by the French chemist Antoine-Jérôme Balard, who recognized it as a previously unknown substance.

Already two years before Balard, the German chemist Justus von Liebig unknowingly produced elemental bromine in 1824. He had been commissioned to analyse the brines of Salzhausen, as the town was planning a spa. While examining these brines, Liebig found a new substance, which he interpreted as iodine chloride. Thirteen years later he admitted that his careless analysis had deprived him of the discovery of a new element. Liebig wrote of this, "I know a chemist who, when he was at Kreuznach, examined the mother liquors of the salt works." He then went on to describe his misfortune, concluding with the words, "Since that time he has put forward no theories unless they have been supported and confirmed by undoubted experiments; and I can report that he has not done badly at that."

Karl Löwig also worked on bromine, which he had already obtained before 1825 by introducing chlorine into Kreuznach brine water, but Balard beat him to the publication of his discovery.

Industrial production began in 1860, and Joseph Louis Gay-Lussac suggested the name "bromine" (Greek for "goat stench of animals") because of its pungent odor.

Justus Liebig was the first to isolate elemental bromine

Occurrence

Bromine occurs in the form of bromides, the salts of hydrobromic acid. In terms of quantity, the largest deposits are found as dissolved bromides in seawater. Deposits of natural salt deposits (rock and potash salts) also contain small amounts of potassium bromide and potassium bromate. Bromine can also occur in the atmosphere in the form of molecular bromine and bromine oxide and can significantly affect atmospheric ozone chemistry, being transported over long distances. During the polar spring, larger concentrations (>10ppt) of BrO regularly destroy almost all tropospheric ozone. These events can also be observed by satellites using the DOAS method. In tropical regions with high bioactivity, strong emissions of halogenated hydrocarbons have been observed, which can ultimately contribute to the formation of BrO and ozone destruction through photolysis.

Bromine is essential for animals in trace amounts. Bromide acts as a cofactor in a metabolic reaction that is necessary for building the collagen IV matrix in connective tissue.

Questions and Answers

Q: What is bromine?

A: Bromine is a chemical element that is part of Group 7 elements or halogens on the periodic table.

Q: What is the atomic number of bromine?

A: The atomic number of bromine is 35.

Q: What does atomic weight mean for bromine?

A: Atomic weight is the average mass of all the isotopes of an element. For bromine, its atomic weight is 80.

Q: Is bromine a diatomic element?

A: Yes, bromine is diatomic. This means that two atoms are stuck together to make a molecule in any bromine sample.

Q: What other elements are part of the halogens group on the periodic table?

A: The halogens group on the periodic table includes fluorine, chlorine, bromine, iodine, and astatine.

Q: What is the chemical symbol for bromine?

A: The chemical symbol for bromine is Br.

Q: How many protons are in a bromine atom?

A: There are 35 protons in a bromine atom, which corresponds to the atomic number of bromine.

Author

Creation date: November 13, 2022

Last updated: May 24, 2026