Summary:
- Fluorine, chlorine, bromine, iodine, and astatine are called the halogens (tan column) The term “halogen” means “salt-former” because these elements will readily react with alkali metal and alkaline earth metals to form halide salts.
- The halogens all have the general electron configuration ns2np5, giving them seven valence electrons.
- They are one electron short of having the full outer s and p sublevel, which makes them very reactive.
- None of these elements are found free in nature because of their reactivity.