Fluorine and Chlorine are two of the elements that make up the group of halides. Halides are a group of chemical elements that contain one or more atoms of either chlorine, fluorine, bromine, or iodine. Fluorine and Chlorine are both highly reactive elements, and they are often used in industrial processes such as water treatment and metal plating. They are also used in many consumer products, such as toothpaste and cleaning products.