Bromine (Br)
“The only nonmetal that stays liquid at room temperature — a dense, blood-red liquid that fumes and stings.”
How its electrons are arranged
Computed from the aufbau principle, with known real-world exceptions applied automatically.
The notes
Characteristics
- One of only two elements liquid at ordinary room temperature (the other is mercury) — and the only liquid nonmetal.
- A halogen of Group 17 with seven valence electrons ([Ar] 3d¹⁰ 4s² 4p⁵): less aggressive than chlorine yet more reactive than iodine, forever hungry for one more electron.
- Forms bromide salts (Br⁻) with metals and the colourless, pungent gas HBr with hydrogen; silver bromide (AgBr) is famously light-sensitive.
- Barely dissolves in water (pale-yellow “bromine water”) but dissolves readily in organic solvents, turning them orange — the classic test for unsaturation in oils and alkenes.
- Both liquid and vapour attack skin, eyes and lungs; bromine burns heal notoriously slowly, so it is treated as one of the laboratory’s nastier customers.
A dense (3.1 g/cm³), deep red-brown liquid that evaporates easily into choking orange-brown vapour. The smell announces it from across a room; even in a fume cupboard chemists handle it with gloves and goggles.
Where you meet it
✦ Uses
- Silver bromide (AgBr) in old-style photographic film — the grains that darkened in the light to capture every photograph of the twentieth century.
- Brominated flame retardants in TV casings, circuit boards and sofa foam — they mop up the free radicals that keep a fire burning.
- Potassium bromide, the Victorian doctor’s nerve-calming sedative — “a bromide” still means a dull, soothing remark.
- Bromine-based disinfectants for swimming pools and industrial cooling towers, working where plain chlorine would be too harsh.
◍ Everyday examples
- Seawater holds about 65 parts per million of bromide — the oceans are Earth’s great bromine reservoir, and many countries harvest the element from brine wells instead.
- The treasured black-and-white photographs in a family album began as specks of silver bromide darkening on film.
- Tyrian purple, the dye reserved for Roman emperors’ robes, is actually a bromine compound (dibromoindigo) squeezed out of sea snails.
History & name
In 1826 the young French chemist Antoine Jérôme Balard, studying the salty brines of Mediterranean marshes near Montpellier, noticed a deep yellow-brown liquid nobody could explain. At first it was taken for a compound of chlorine and iodine, but Balard proved it was a brand-new element. A German student, Carl Jacob Löwig, had actually isolated the same substance from spa water in 1825, yet Balard published first and kept the credit. For its dreadful smell the element was named bromine, from the Greek brōmos, “stench”.