They are group of elements. Most of the lanthanides and actinides are radioactive.
Halogens are a group of non metals with valency -1.
halogen means salt makers. They combine with metals or metal like radicals to form salts (eg, Nacl, BaCl₂, NH₄Cl). They also combine with hydrogen to form acids (eg, HCl, HBr, HF etc). The halogens are toxic. Their toxicity decreases with increase in weight. The halogens are Fluorine(F), Chlorine(Cl), Bromine(Br), Iodine(I), Astatine(At), and artificially created element 117 called Ununseptium(Uus).