Symbol

At

Atomic Number

85

Atomic Mass

209.9871

Family

Group 17 (Viia) Halogen Pronunciation

AS-tuh-teen

Overview

Astatine is a member of the halogen family, elements in Group 17 (VIIA) of the periodic table. It is one of the rarest elements in the universe. Scientists believe that no more than 25 grams exist on the Earth's surface. All isotopes of astatine are radioactive and decay into other elements. For this reason, the element's properties are difficult to study. What is known is that it has properties similar to those of the other halogens— fluorine, chlorine, bromine, and iodine. Because it is so rare, it has essentially no uses.

Discovery and Naming

The periodic table is a chart that shows how the chemical elements are related to each other. The periodic table was first constructed by Russian chemist Dmitri Mendeleev (1834-1907) in the early 1870s.

Mendeleev's periodic table contained some empty boxes. At first, no...