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. A more reactive halogen displaces a less reactive one from its compound. In 1940, D. R. Corson, K.R. Astatine has found uses in medicine even though it is radioactive and decays quickly. Astatine is the least chemically reactive of the halogens and exhibits the most metallic properties of the halogen group. Bromine liquid evaporates easily at room temperatures emitting an orange vapor. Astatine is radioactive and rapidly decays to other, more stable elements. It gets its name from the Greek word "bromos" which means "stench." Q: Based on their position in the periodic table from the Figure above, how many valence electrons do you think halogens have? The first halogen to be isolated and recognized as an element was chlorine. Why? Since the binary compounds of halogen are the most abundant soluble salts found in the sea. A: The number of valence electrons starts at one for elements in group 1. Thus halogen means salt producers. Scientists believe that no more than 25 grams exist on the Earth's surface. 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 also react with hydrogen to form hydrogen astatide, which when dissolved in water, forms hydroastatic acid. Astatine is a member of the halogen family, elements in Group 17 (VIIA) of the periodic 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. Would you expect Astatine to be more or less reactive than iodine? astatine. Colourless. iodine (brown) and sodium chloride. All isotopes of astatine are radioactive and decay into other elements. The last element Astatine is radioactive and is very short lived hence generally excluded from the study. Astatine-211 is sometimes used as a radioactive tracer and in cancer treatment. Astatine is a halogen and it is quite possible that it accumulates in the human thyroid just like iodine. Bromine has a very strong and bad odor. The word halogen is derived from the Greek words Halos (Sea Salt) and Genes (Producer). The astatine halogen bond also completes a periodic set that has attracted growing interest in recent years. As a result, it is one of the least common elements on Earth. 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 radioactive and rapidly decays to other, more stable elements. What colour is chlorine when dissolved in water? 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