Group 7, also known as the halogens, consists of five chemical elements: fluorine, chlorine, bromine, iodine, and astatine. These elements are located in the second column from the right on the periodic table. They are known for their high reactivity, especially with alkali and alkaline earth metals, forming various compounds. The halogens exist in different physical states at room temperature: fluorine and chlorine are gases, bromine is a liquid, and iodine and astatine are solids. They have seven electrons in their outermost shell, which makes them eager to gain one more electron to achieve a stable configuration.