Structure
Not a diagram of dots on rings — a Monte-Carlo sample of the actual probability density |ψ|² for each occupied subshell. Drag to rotate. Blue and violet mark opposite signs of the wavefunction, which is what makes bonding possible.
Measured values
Every bar shows where bromine sits among all 118 elements for that property.
Sources: IUPAC 2021 standard atomic weights · CRC Handbook of Chemistry and Physics · NIST. Values marked ~ are predicted rather than measured.
Size, to scale
Radius 120 pm — that is 0.12 nm, so about 4167 million of them side by side would span a millimetre.
Thermal range
Bromine is liquid over a 66 K window, from 266 K to 332 K.
Where it sits
Bromine sits in period 4, group 17. Everything in group 17 shares the same outer-electron count, which is why they behave so similarly.
OTHER HALOGENS
All halogensThe story
Bromine is the only liquid non-metal at room temperature and one of the most reactive elements on Earth. This dark reddish-brown liquid with its choking, penetrating odor is both fascinating and dangerous. The name comes from the Greek word "bromos" meaning stench, which perfectly describes its powerful, unpleasant smell that can be detected at extremely low concentrations. Discovered in 1826 by French chemist Antoine-Jérôme Balard while studying seaweed ash from the Mediterranean coast, bromine was initially dismissed by other chemists who thought it was just a chlorine-iodine compound. Balard had to prove repeatedly that he had discovered a new element. Interestingly, German chemist Carl Jacob Löwig had isolated bromine independently around the same time from mineral water, but Balard published first. What makes bromine absolutely unique is its physical state - it's one of only two elements that are liquid at room temperature (mercury being the other). Bromine easily evaporates to form toxic orange-brown vapors that are denser than air, creating dramatic demonstrations in chemistry classes. Its reactivity is intense - it readily attacks organic materials, metals, and even reacts with water. Bromine has played crucial roles in photography, medicine, and industry. Silver bromide was essential for photographic film because it darkens when exposed to light. Bromide compounds were once widely used as sedatives (hence the phrase "taking a bromide" meaning something boring or calming). Today, bromine compounds are essential flame retardants, protecting everything from furniture to electronics from fire. Here's something remarkable: bromine is concentrated in seawater and salt lakes, with the Dead Sea containing the highest natural concentrations. Israel extracts vast amounts of bromine from the Dead Sea, making it a major global producer of this valuable element.
Antoine-Jérôme Balard discovered bromine in 1826 while studying seaweed ash from Mediterranean salt marshes. The distinctive red-brown vapor and pungent odor led Balard to identify this new halogen element, which he named from the Greek "bromos" meaning stench.
Applications
Bromine's exceptional effectiveness as a flame retardant has saved countless lives by preventing fires in electronics, textiles, and transportation, while its chemical reactivity enables diverse applications from photography to oil drilling.
Brominated flame retardants interrupt combustion chain reactions at the gas phase, providing superior fire protection compared to other halogen systems. Electronics applications include computer circuit boards, television casings, and automotive components where fire safety is critical for consumer protection and regulatory compliance.
Drilling fluids use bromine compounds to increase density and control formation pressures in deep oil wells. Completion fluids containing cesium bromide or zinc bromide enable safe well completion in high-pressure, high-temperature environments where conventional fluids would fail.
Bromine disinfection provides effective biocide action in swimming pools, spas, and cooling towers with better pH stability than chlorine systems. Industrial water treatment uses bromine-based biocides to control microbial growth in recirculating systems and prevent biofilm formation.
Where it comes from
2.4 mg/kg of Earth's crust · more abundant than 59% of elements
Bromine concentrates in seawater through evaporation and geological processes, with the Dead Sea containing the world's highest bromine concentrations at 4,000-5,000 ppm. Most commercial bromine extraction utilizes seawater or underground brines rather than solid mineral sources.
Seawater processing recovers bromine through chlorine oxidation followed by steam distillation, while underground brine wells in Arkansas and Israel provide concentrated bromine sources. The Smackover Formation in Arkansas contains brines with bromine concentrations exceeding 4,000 ppm.
Handling
Bromine liquid and vapor are extremely corrosive and toxic, requiring comprehensive safety measures for handling and storage. Emergency response procedures are critical due to bromine's potential for severe chemical burns and respiratory damage.
Full-face respirators, acid-resistant clothing, and emergency shower/eyewash stations are mandatory for bromine handling. Vapor detection systems and emergency ventilation prevent dangerous accumulations in work areas.
Quick answers
Bromine (symbol Br) is element 35 on the periodic table, a halogen in period 4, group 17. One of only two elements that are liquid at room temperature, and the one that smells like a swimming pool from hell. At room temperature it is a liquid.
[Ar] 3d¹⁰ 4s² 4p⁵, giving 4 occupied shells holding 2, 8, 18, 7 electrons respectively. Its outer shell holds 7 electrons, which is what sets its bonding behaviour.Bromine melts at 265.8 K (-7.3 °C) and boils at 332 K (58.9 °C). It will melt in a warm room or in the palm of your hand.
The standard atomic weight of Bromine is 79.904 u. That is a weighted average across its naturally occurring isotopes, which is why it is rarely a whole number.
Bromine has a density of 3.103 g/cm³. Water is 1.0 g/cm³, so a block of bromine is about 3.1× heavier.
Bromine has a Pauling electronegativity of 2.96. The scale runs from 0.70 (francium, the least greedy for electrons) to 3.98 (fluorine, the most). A value this high means it tends to pull electrons away from almost anything it bonds with.
Bromine was discovered in 1826 by Antoine Balard. It is named after greek bromos, "stench".
Bromine makes up about 2.4 mg/kg of the Earth's crust — uncommon, but not rare.