Astatine can also react with hydrogen to form hydrogen astatide, which when dissolved in water, forms hydroastatic acid. Uses of Astatine. Astatine is also studied in a few nuclear research laboratories in which the high radioactivity of the element requires a special kind of handling techniques and precautions to be taken. Astatine is a member of the halogen family, elements in Group 17 (VIIA) of the periodic table. Astatine is the heaviest of the halogens and is essentially unavailable in nature with less than one teaspoon of the element found in the Earth’s crust at any one time. Since the binary compounds of halogen are the most abundant soluble salts found in the sea. Why? Astatine is the least chemically reactive of the halogens and exhibits the most metallic properties of the halogen group. Astatine is a halogen and it is quite possible that it accumulates in the human thyroid just like iodine. The first halogen to be isolated and recognized as an element was chlorine. The word halogen is derived from the Greek words Halos (Sea Salt) and Genes (Producer). The last element Astatine is radioactive and is very short lived hence generally excluded from the study. astatine. Astatine-211 is sometimes used as a radioactive tracer and in cancer treatment. Colourless. Q: Based on their position in the periodic table from the Figure above, how many valence electrons do you think halogens have? A: The number of valence electrons starts at one for elements in group 1. Thus halogen means salt producers. As a result, it is one of the least common elements on Earth. The astatine halogen bond also completes a periodic set that has attracted growing interest in recent years. iodine (brown) and sodium chloride. Astatine is radioactive and rapidly decays to other, more stable elements. Bromine has a very strong and bad odor. It is one of the rarest elements in the universe. Astatine is the least reactive of the halogens but just like the rest of them it combines with hydrogen to make hydrogen astatide which dissolves in water to make hydroastatic acid; it is just like a weaker version of hydrochloric acid. If you could ever isolate enough of this stuff astatine would be an even darker purple solid than iodine. What colour is chlorine when dissolved in water? It gets its name from the Greek word "bromos" which means "stench." Astatine has found uses in medicine even though it is radioactive and decays quickly. What are displacement reactions? As a result, it is one of the least common elements on Earth. In 1940, D. R. Corson, K.R. Astatine is radioactive and rapidly decays to other, more stable elements. Figure \(\PageIndex{1}\): Halogens reside in group 17 of the periodic table, in this case the green column on the right side of the table. Astatine can be produced by bombarding bismuth with energetic alpha particles to obtain the relatively long-lived 209-211 At, which can be distilled from the target by heating in air. Scientists believe that no more than 25 grams exist on the Earth's surface. Would you expect Astatine to be more or less reactive than iodine? All isotopes of astatine are radioactive and decay into other elements. A more reactive halogen displaces a less reactive one from its compound. Bromine liquid evaporates easily at room temperatures emitting an orange vapor.