Bromide (Br⁻) is a negatively charged ion, known as an anion, derived from the element bromine. It is commonly found in various compounds, such as sodium bromide (NaBr) and potassium bromide (KBr). Bromide ions play a role in several chemical reactions and are used in various applications, including photography and water treatment. In nature, bromide is often present in seawater and certain mineral deposits. It is also used in medicine, particularly in sedatives and anticonvulsants. The presence of bromide in the environment can be monitored due to its potential effects on human health and ecosystems, making it an important subject of study in environmental science.