Halogens are a group on the periodic table made up of five non-metallic elements - fluorine (F), chlorine (Cl), Bromine (Br), Iodine (I) and Astatine (At). Element 117 - ununseptium - which has been chemically created, may also be considered a halogen.
The word halogen means salt-producing; as halogens and metals react, they produce salts like sodium chloride (common table salt), calcium fluoride, silver bromide and potassium iodide. At standard temperature and pressure, halogens contain elements in three of the main states of matter. The three in the middle - chlorine, bromine, and iodine - are often used as disinfectants, and others are used as flame retardants.
Halogens are also used in lamps that glow at a higher temperature with a whiter light that lasts longer than traditional incandescent bulbs.
Halogens are highly reactive with water, other halogens, metals, and hydrogen. They have a high level of electronegativity, which means that they may have extreme reactions that can be lethal to dangerously toxic.