The halogens (Group 17) are non-metallic elements and include: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). Ununseptium (Uus) may also be a halogen. They are odorless, colorless, and non-flammable. Halogens react readily with metals to form salts (halogen means ‘salt-former’).