The element occupying position 35 on the periodic table is Bromine, symbolized as \(\text{Br}\). This element belongs to Group 17, known as the halogens, a family of highly reactive nonmetals that includes fluorine, chlorine, and iodine. Bromine’s unique placement and characteristics have made it a substance of considerable scientific and industrial importance.
Fundamental Characteristics of Bromine
At standard room temperature and pressure, Bromine is one of only two elements, and the sole nonmetal, to exist in a liquid state. This dense fluid is characterized by a deep, reddish-brown color.
The liquid is highly volatile, readily evaporating to produce a similarly colored, dense vapor. This vapor has a strong, pungent odor, which is the origin of the element’s name, derived from the Greek word bromos, meaning “stench”. Its relatively low melting point of \(-7.2^\circ\text{C}\) and boiling point of \(58.8^\circ\text{C}\) underscore this volatility.
As a halogen, Bromine is highly reactive, possessing seven valence electrons and requiring only one additional electron to complete its outer shell. This configuration makes it a strong oxidizing agent, forming compounds known as bromides. Its reactivity sits between that of chlorine and iodine, and it is rarely found in its pure elemental form, instead occurring primarily as bromide salts dissolved in seawater and underground brines.
Industrial and Commercial Applications
Bromine’s unique chemical properties, particularly its reactivity and fire-suppressing capabilities, have led to widespread industrial use. One major application is in the manufacturing of brominated flame retardants (BFRs). These compounds are integrated into plastics, textiles, and electronics to reduce the flammability of consumer products.
The fire-suppressing mechanism relies on Bromine interfering with the chemical reactions of combustion. When exposed to heat, BFRs decompose and release hydrogen bromide gas. This gas disrupts the free radical chain reactions that propagate a fire, quickly extinguishing the flame or significantly slowing its spread.
Bromine compounds are also utilized in water treatment as disinfectants, often serving as an alternative to chlorine. Compounds like sodium bromide and bromine chloride sanitize swimming pools, spas, and industrial cooling towers. Bromine-based sanitizers are particularly useful for heated water applications because they maintain effectiveness over a wider range of \(\text{pH}\) and at higher temperatures.
Bromine is also a component in clear brine fluids, which are high-density salt solutions used in oil and gas exploration. These fluids, including zinc bromide or calcium bromide, are essential for controlling downhole pressure during drilling and completion operations. Historically, Bromine compounds were also used in film photography and in earlier pharmaceutical applications as sedatives and anticonvulsants.
Biological Interactions and Health Implications
Elemental Bromine and its vapors are highly corrosive and toxic upon direct contact or inhalation. Exposure to the reddish-brown vapor causes severe irritation to the respiratory tract, leading to coughing, choking, and shortness of breath. Direct contact with the liquid results in deep chemical burns on human tissue.
A common concern involves exposure to certain organobromine compounds, such as polybrominated diphenyl ethers (\(\text{PBDEs}\)). These compounds persist in the environment because they do not easily break down. They can bioaccumulate, building up in the fatty tissues of living organisms, and environmental accumulation has been linked to adverse effects on the nervous and endocrine systems.
The bromide ion (\(\text{Br}^-\)) behaves similarly to the chloride ion in the body and is found in trace amounts in human tissues. While Bromine is not considered an essential nutrient for humans, it may play a role in the synthesis of collagen, a protein fundamental to tissue structure. Chronic exposure to excessive amounts of bromide can lead to bromism, characterized by neurological symptoms like confusion, irritability, and psychosis, due to the ion’s depressive effect on the central nervous system.