What is Bromine's atomic number?

Bromine has atomic number 35, meaning it has 35 protons in its nucleus. Its chemical symbol is Br, derived from the Greek bromos meaning "stench."

Why is Bromine a liquid at room temperature?

Bromine is a liquid at room temperature (melting point -7.2 °C) because its large, polarizable electron cloud creates relatively strong London dispersion forces between Br2 molecules — stronger than in lighter halogens like chlorine but weaker than in iodine, placing it in the liquid range at 25 °C.

What is Bromine used for today?

Major uses include organobromide flame retardants (electronics, textiles), fumigants (methyl bromide), pharmaceutical intermediates, photography (silver bromide), water treatment, and drilling fluids for oil and gas wells.

Is Bromine dangerous?

Yes. Bromine vapor is toxic and corrosive; inhalation can cause severe respiratory damage. Liquid bromine causes chemical burns on contact with skin. The IDLH (immediately dangerous to life and health) concentration is 3 ppm in air.

What is Bromine's electron configuration?

Bromine's full electron configuration is [Ar] 3d10 4s2 4p5. The five 4p electrons give it a strong tendency to gain one electron (oxidation state -1), characteristic of all halogens, though +1, +3, +5 states also occur in compounds.

How was Bromine discovered?

Bromine was discovered independently in 1825 by Antoine Balard in France and Carl Jacob Löwig in Germany. Balard isolated it from the mother liquor of sea salt and is generally credited with its discovery.

Bromine Element Properties

Explore the complete physical and chemical properties of Bromine (Br, element 35) — one of only two elements that are liquid at room temperature.

79.904

Bromine

Halogen · Period 4 · Group 17

Melting Point

-7.2 °C

Boiling Point

58.8 °C

Density

3.103 g/cm³

Atomic Mass

79.904 u

Electron Shell Configuration

[Ar] 3d¹⁰ 4s² 4p⁵

Shells: 2, 8, 18, 7

Filter Properties

Property	Value
Element Name	Bromine
Symbol	Br
Atomic Number	35
Atomic Mass	79.904 u (range: 79.901–79.907)
Category	Halogen (nonmetal)
Group	17 (VIIA / Halogens)
Period	4
Block	p-block
CAS Number	7726-95-6
Discovered	1825
Discovered By	Antoine Balard (France); Carl Löwig (Germany)
Named After	bromos (Greek: stench)
Standard State	Liquid at 25 °C
Appearance	Fuming red-brown liquid with pungent odor
Notable Fact	One of only two liquid elements at room temperature

Property	Value
Electron Configuration	[Ar] 3d10 4s2 4p5
Electrons Per Shell	2, 8, 18, 7
Number of Protons	35
Number of Neutrons (Br-79)	44
Number of Electrons	35
Valence Electrons	7
Oxidation States	-1, 0, +1, +3, +4, +5, +7
Electronegativity (Pauling)	2.96
Electron Affinity	324.5 kJ/mol
First Ionization Energy	1139.9 kJ/mol
Second Ionization Energy	2103 kJ/mol
Third Ionization Energy	3470 kJ/mol
Atomic Radius (calc.)	120 pm
Covalent Radius	114 pm
Van der Waals Radius	185 pm
Stable Isotopes	Br-79 (50.69%), Br-81 (49.31%)

Property	Value
Melting Point	-7.2 °C (19 °F / 265.9 K)
Boiling Point	58.8 °C (137.8 °F / 331.9 K)
Critical Temperature	315 °C (588 K)
Critical Pressure	10.34 MPa
Density (liquid, 25 °C)	3.103 g/cm³
Density (gas, 0 °C)	7.59 g/L
Heat of Fusion	10.57 kJ/mol
Heat of Vaporization	29.96 kJ/mol
Specific Heat Capacity	0.474 J/(g·K)
Thermal Conductivity	0.122 W/(m·K) (at 300 K, gas)
Electrical Resistivity	~7.8×10⁹ Ω·m (liquid, insulator)
Surface Tension	40.95 mN/m (at 20 °C)
Viscosity (liquid)	0.944 mPa·s (at 25 °C)
Crystal Structure	Orthorhombic (solid Br2)
Magnetic Ordering	Diamagnetic
Speed of Sound (gas)	218 m/s (at 0 °C)

Property	Value
Reactivity	Highly reactive; strong oxidizing agent
Reaction with Air	Reacts slowly; forms HBr in moist air
Reaction with Water	Disproportionates: Br2 + H2O → HBr + HBrO
Reaction with Metals	Reacts vigorously; forms metal bromides
Reaction with Hydrogen	H2 + Br2 → 2 HBr (less vigorous than Cl2)
Common Compounds	HBr, NaBr, KBr, AgBr, CH3Br, CBr4, NaBrO3
Flame Retardant Use	Organobromides interrupt radical chain reactions in combustion
Pharmaceutical Role	C–Br bonds in drug synthesis; anticonvulsants (KBr)
Photography Use	Silver bromide (AgBr) light-sensitive emulsions
Oxidation State Range	-1 (most common), +1, +3, +5, +7
Halogen Behavior	Strong oxidizer; accepts one electron readily
Toxicity	Corrosive vapor; IDLH 3 ppm; causes chemical burns
Natural Occurrence	Seawater (~65 mg/L), brine deposits, Dead Sea
Global Production	~600,000 tonnes/year (brine extraction)

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Summary

Bromine (Br) is element 35 on the periodic table, a halogen in group 17 and period 4. It is one of only two pure elements that exist as a liquid at room temperature (the other being mercury), appearing as a fuming red-brown liquid with a pungent odor. This reference tool presents all key physical, atomic, and chemical properties of Bromine in one organized view, including its uses in flame retardants, photography, and pharmaceuticals.

How it works

All Bromine property data is embedded directly in the page — no server call is needed.
Use the section tabs (Overview, Atomic, Physical, Chemical) to navigate different property groups.
Click any property row to copy its value to your clipboard.
The electron configuration diagram shows the shell distribution visually.
Use the search box to filter properties by name.

Use cases

Quick reference for students studying the periodic table halogens.
Verify Bromine specs during flame-retardant or materials research.
Teaching aid for illustrating properties of room-temperature liquid elements.
Cross-check Bromine isotope and toxicology data for lab work.
Explore Bromine's role in pharmaceutical synthesis and disinfection.
Support chemistry homework and exam preparation.
Reference oxidation states for organic halogen chemistry problems.
Look up thermodynamic data for thermochemistry calculations.

Frequently Asked Questions

Last updated: 2026-09-30 · Reviewed by Nham Vu