ElementsWhat is bromine?
Bromine is a dark red-brown liquid that gives off a choking vapour. It is one of only two elements that are liquid at room temperature. It is taken from salt lakes and sea water.
What is bromine used for?
Flame retardants, water treatment, and chemicals for medicines and photography.
Where the name comes from
From the Greek word bromos, stench, for its strong smell.
Key facts
- Symbol
- Br
- Atomic number
- 35
- Atomic mass
- 79.90 u
- Family
- Halogen
- Period
- 4
- Group
- 17
- Block
- p
- State at room temperature
- Liquid
- Melting point
- -7.2 °C (265.95 K, 19 °F)
- Boiling point
- 58.8 °C (331.95 K, 138 °F)
- Density
- 3.11 g/cm³
- Electrons per shell
- 2, 8, 18, 7
- Electron configuration
- [Ar]4s2 3d10 4p5
- Common oxidation states
- +5, +1, -1
- Electronegativity (Pauling)
- 2.96
- First ionisation energy
- 11.814 eV
- Electron affinity
- 3.365 eV
- Atomic radius (van der Waals)
- 183 pm
- Discovered
- 1826
Place in the periodic table
Bromine is element number 35. It sits in period 4 (row 4) of the periodic table, in group 17 (column 17), and belongs to the p-block. Just before it comes selenium (34), and just after it comes krypton (36). In the same column, chlorine is above it and iodine is below it. Elements in one column tend to behave alike.
Family: Halogens.
Physical properties
At room temperature bromine is a liquid. It melts at -7.2 °C and boils at 58.8 °C, so it stays liquid over a range of 66 degrees. Its density is 3.11 grams per cubic centimetre, so a one-litre block would weigh about 3.11 kilograms. By density it ranks 69th among the 96 elements with a measured value.
Inside the atom
An atom of bromine has 35 protons in its nucleus and, when neutral, 35 electrons around it. The electrons are arranged in 4 shells: 2, 8, 18, 7. The outermost shell holds 7 electrons. Written in full, the electron configuration is [Ar]4s2 3d10 4p5.
Its electronegativity on the Pauling scale is 2.96. This number shows how strongly an atom pulls shared electrons towards itself: fluorine, the strongest, is 3.98. Removing one electron from an atom takes 11.814 electronvolts (about 1,140 kilojoules per mole). One mole of bromine weighs 79.90 grams, so a single gram contains about 7.54 × 1021 atoms.
The ring picture is a simple model that only counts the electrons in each shell. Real atoms do not look like this.
Next steps
- Work out the weight of a compound that contains bromine with the molar mass calculator.
- Compare it with every other element in the sortable list.
- Test yourself with the symbol quiz.
Figures on this page are from PubChem (U.S. National Library of Medicine), as downloaded on 11 November 2026. See About and data sources.