Astatine is classed as a halogen and a non metal. It was predicted to exist by Mendeleev and he called it eka-iodine. Astatine however could not be found in nature but was made in the lab in 1940. It was made by Dale Coson, Kenneth Ross Mackenzie and Emilio Segrè by bombarding bismuth with alpha particles. It is very unstable and breaks down quickly. Its uses are in cancer treatment and as a tracer due to its very short half life. It is a solid non metal at room temperature with a melting point of 302°c and a boiling point of 336°c. Astatine like Iodine can be absorbed by the thyroid, in animal studies due to its radioactivity it was discovered that this causes greater damage that iodine due to astatine being easily absorbed by animal thyroids.
D.R.Corson, K.R.MacKenzie, E.Segré