Category: Halogen
Atomic Number: 35
Period: 4 | Group: 17
Block: p-block
One of only two elements that are liquid at room temperature, and the one that smells like a swimming pool from hell.
| Property | Value |
|---|---|
| Phase at STP | Liquid |
| Density | N/A |
| Melting Point | 265.80 K (-7.35 °C) |
| Boiling Point | 332.00 K (58.85 °C) |
| Heat Capacity | N/A |
| Property | Value |
|---|---|
| Atomic Mass | 79.9040 u |
| Electronegativity (Pauling) | N/A |
| Oxidation States | -1, +1, +3, +5, +7 |
| Electron Configuration |
| Discovered By | Unknown |
|---|---|
| Discovery Year | 1826 |
| Named After | Greek bromos, "stench" |
Two discoverers (1825 and 1826)
In 1825 the German student Carl Jacob Löwig obtained a red-brown liquid from the water of a mineral spring at Bad Kreuznach, but his publication was delayed. In 1826 Antoine-Jérôme Balard, a young chemist in Montpellier, found the same substance in the brine of salt marshes after treating it with chlorine, and published first, so he is credited with the discovery.
The name
Balard first proposed the name muride, from the Latin muria, brine; it was changed to brome, from the Greek bromos, meaning stench, because of its strong smell.
Early uses
Bromides were soon used in photography and, from the 1850s, as the first effective sedatives and anticonvulsants.
| ISOTOPE | Neutrons | Natural Abundance | Half-life | Decay Mode |
|---|---|---|---|---|
| Br-79 | 44 | 50.65% | Stable | - |
| Br-81 | 46 | 49.35% | Stable | - |
Data: IAEA Nuclear Data Section, LiveChart of Nuclides, ground-state evaluations, retrieved October 10, 2026. Abundance is the share of atoms in the natural element; a dash means the isotope has no standard natural abundance.
Flame retardants
The largest use of bromine is in brominated flame retardants for plastics in electronics, cables, insulation and furniture. Some of these, such as polybrominated diphenyl ethers (PBDEs), persist in the environment and are now banned or restricted under the Stockholm Convention.
Oil and gas, water and energy
Drilling fluids: dense solutions of calcium, sodium and zinc bromide control pressure in oil and gas wells.
Water treatment: bromine compounds disinfect swimming pools, hot tubs and cooling towers.
Mercury control: adding bromide to coal helps capture mercury from power plant emissions.
Batteries: zinc-bromine flow batteries store electricity for the grid.
Chemicals and medicine
Bromine is a building block for pharmaceuticals, dyes and agricultural chemicals, and silver bromide was the light-sensitive compound of photographic film. Methyl bromide, once a widely used soil fumigant, has been phased out under the Montreal Protocol, apart from quarantine and pre-shipment uses, because it damages the ozone layer. Ethylene dibromide, once added to leaded gasoline, largely disappeared with leaded fuel.
| Earth's Crust | N/A |
|---|---|
| Universe | N/A |