Group 17 Elements

Group 17 of the periodic table brings together fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and the radioactive elements astatine (At) and tennessine (Ts). As a family they are called the halogens, a name drawn from the Greek halo (salt) and genes (born) — "salt-formers" — because of how readily they unite with metals to give salts.

The halogens are strongly non-metallic and rank among the most reactive elements in the periodic table. Much like Groups 1 and 2, Group 17 shows an unusually tight family resemblance: F, Cl, Br and I behave more like one another than the members of most other groups do, and their physical and chemical properties change smoothly and predictably as you descend the group. Astatine and …