Halogens are a group of chemical elements found in Group 17 of the periodic table. This group includes five elements: fluorine, chlorine, bromine, iodine, and astatine. Halogens are known for their high reactivity, especially with alkali metals and alkaline earth metals, forming salts. They exist in various states at room temperature, with fluorine and chlorine being gases, bromine a liquid, and iodine and astatine solids. These elements have seven electrons in their outermost shell, making them eager to gain one more electron to achieve a stable configuration. Halogens are commonly used in various applications, such as chlorine in water purification and iodine in antiseptics. Their reactivity and ability to form compounds make them essential in both industrial and biological processes.