Bromine (Br), atomic number 35, is classified as a nonmetal. It is unique among nonmetals because it is one of only two elements on the periodic table that exists as a liquid at standard room temperature, the other being mercury. Bromine presents as a dense, reddish-brown liquid that readily vaporizes into a similarly colored gas.
Bromine’s Position on the Periodic Table
Bromine is located on the right side of the periodic table in Group 17, known as the Halogens. This family includes fluorine, chlorine, and iodine, all sharing similar chemical tendencies.
The placement in Group 17 provides Bromine with its characteristic electron configuration. A bromine atom possesses seven valence electrons in its outermost shell, leaving it just one electron short of achieving a stable noble gas configuration.
This deficiency makes bromine highly reactive, as it has a strong tendency to gain an electron from other atoms. This eagerness to accept an electron is a defining characteristic of nonmetals, contrasting with metals, which typically lose valence electrons. This behavior allows bromine to form a negatively charged bromide ion (Br-) when reacting with metals.
Physical and Chemical Properties of Bromine
The physical state of bromine at room temperature is its most distinct characteristic, as it is the only nonmetal that is a liquid under normal conditions. This dense, dark red-brown liquid has a low melting point of about -7.2°C and a low boiling point of approximately 58.8°C. Upon vaporization, it emits a pungent, irritating vapor. Its name is derived from the Greek word bromos, meaning “stench.”
Unlike metals, bromine is a poor conductor of both electricity and heat. It also lacks the metallic luster typically seen in metals, presenting instead with a dull appearance. This poor conductivity is a general property of nonmetals, where valence electrons are tightly bound and not free to move.
Chemically, bromine exhibits high electronegativity, which measures an atom’s ability to attract electrons. It ranks below fluorine and chlorine in reactivity, but above iodine, following the trend within the Halogen group. Elemental bromine naturally exists as a diatomic molecule (Br2), where two bromine atoms share a single covalent bond.
Its high reactivity enables it to form compounds with nearly all elements, either by gaining an electron to form ionic bonds with metals or by sharing electrons to form covalent bonds with other nonmetals. This electron-accepting property makes elemental bromine a strong oxidizing agent.
Common Applications and Natural Occurrence
Bromine does not occur in its elemental form in nature due to its high reactivity; instead, it is found primarily in compounds known as bromides. The most significant natural reservoirs are found dissolved in water, specifically in seawater, saltwater lakes, and underground brine wells. While seawater contains an average of about 65 parts per million of bromide, sources like the Dead Sea and deep brine wells can contain significantly higher concentrations.
Commercially, a large proportion of manufactured bromine is used in the production of brominated flame retardants (BFRs). These compounds are added to plastics, textiles, and electronics to reduce their flammability and slow down ignition.
Bromine compounds also have widespread use in agriculture, utilized in the synthesis of fungicides and herbicides.
Additionally, bromine is employed in water treatment as a disinfectant for swimming pools and industrial cooling systems, often serving as an alternative to chlorine. It is also found in various pharmaceuticals, dyestuffs, and historically in photographic film through the use of silver bromide.