As chemists would expect, it acts more like a metal than iodine, the element just above it in the table. Those experiments show that astatine is chemically similar to the other halogens above it in Group 17 of the periodic table. The most complete experiments on astatine were begun in 1966 at the Argonne National Laboratory, out-side Chicago, Illinois. No melting point, boiling point, or density is specified for astatine. The element breaks down too fast to allow experiments that take more than a few hours. The properties of astatine are not well known. (See under "Isotopes" for more information.) In Greek, the word for "unstable" is astatos. Segr è's team suggested the name astatine for element 85 because there are no stable isotopes for the element. The particles collide with atoms, causing the atoms to break apart into other elements. In a cyclotron, small particles, such as protons, are made to travel at high speeds. A cyclotron is a particle accelerator, or atom smasher. Mackenzie, and Emilio Segre (1905-89) found evidence of element 85 at the end of an experiment they were conducting with a cyclotron. ![]() In 1940, three chemists working at the University of California at Berkeley found evidence of element 85. They decided his results must have been incorrect. (Allison was born in Virginia and worked at the Alabama Polytechnic Institute.) Unfortunately for Allison, other chemists could not repeat his experiments successfully. He proposed the names virginium and alabamine for these two elements. For example, American chemist Fred Allison (1882-1974) announced in 1931 that he had discovered elements 85 and 87. Along the way, a number of incorrect answers were proposed. During the first third of the twentieth century, chemists worked very hard to find these two missing elements. Two of the most troubling empty boxes were elements 85 and 87. A search began for elements to fill the half dozen or so boxes that still remained in the periodic table. By the early 1900s, however, chemists had decided that the empty boxes must be spaces for elements that had not yet been discovered. At first, no one was sure what these empty boxes meant. Mendeleev's periodic table contained some empty boxes. The periodic table was first constructed by Russian chemist Dmitri Mendeleev (1834-1907) in the early 1870s. The periodic table is a chart that shows how the chemical elements are related to each other. Because it is so rare, it has essentially no uses. What is known is that it has properties similar to those of the other halogens - fluorine, chlorine, bromine, and iodine. For this reason, the element's properties are difficult to study. All isotopes of astatine are radioactive and decay into other elements. Scientists believe that no more than 25 grams exist on the Earth's surface. It is one of the rarest elements in the universe. OverviewĪstatine is a member of the halogen family, elements in Group 17 (VIIA) of the periodic table. Note: This article, originally published in 1998, was updated in 2006 for the eBook edition.
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