Fluorine belongs to group number 17, which is the halogen family of elements that also includes astatine, iodine, bromine and chlorine. The element fluorine is a highly reactive gas at room temperature that is not found freely in nature. Fluorine has a melting point of 363.32 degrees F, a boiling point of 306.62 degrees F and a density of 0.001696 grams per cubic centimeter.
Fluorine has an atomic weight of 18.9984032 and is assigned the period number 2 and atomic number 9 on the periodic table of elements. Fluorine is an ingredient in toothpaste and is also widely used in city water supplies in a quantity of one part per million to aid in the prevention of tooth decay.