The halogen family of elements contains the most active nonmetals. This family is found in Group VIIA, which is the next-to-last column in the periodic table. The halogens are fluorine, chlorine, bromine, iodine and the radioactive element astatine.
The halogen family is the most reactive family of nonmetals because these elements are close to filling their outermost shell. They have seven valence electrons and only need to receive one more electron to complete the shell. All six elements form diatomic molecules, which are those consisting of two of the same element bonded together. They are highly toxic to humans and are violent reactors with water. This family of elements takes its name from the Greek words "hals" and "gennan," which means "to form salt," because they have the ability to form salts.