Radioactive halogen m.p. 302 ºC; 576 ºF b.p. 337 ºC; 639 ºF density ?	memory peg
	1940 Dale R. Corson, Kenneth R. Mackenzie, and Emilio Segrè, United States (California)
	αστατος (astatos) = unstable (Greek)

The element was first characterized in 1940 by Dale R. Corson (1914-), Kenneth R. Mackenzie (1912-2002), and Emilio Segrè (1905-1989), who synthesized the isotope ²¹¹At by bombarding Bismuth with alpha particles. They observed chemical behavior somewhat similar to that of other halogens. They have named the new element Astatine, from the Greek αστατος [astatos] = restless, unstable, because the element has no stable isotopes; and the suffix -ine because that is usual for halogens (note). If one succeeds in producing the element, the instability is very clear. The isotope ²¹¹At has a half life on only 8.3 hours.

The existence of element #85 was predicted by Д.И. Менделеев (D.I. Mendeleyev) and named by him Eka-Iodine. It was obvious that it must possess interesting properties: the activity of halogens, combined with metallic properties as its neighbour Polonium. Therefore from the end of the 19th century searches were done for this element in different minerals. Especially after in 1920 the German chemist E. Wagner drew again attention to the still hypothetical fifth member of the group of halogens, asserting that this element must be radioactive, the search was intensified. Several times appeared reports about its discovery, however, since we know now that all isotopes of element #85 are highly radioactive, and the amount present in nature is very small, it is clear that these early reports must be erroneous.

From 1925 through 1943 six reports were published on the discovery of element #85. The authors of the imaginary discoveries gave different names to it (note):

• 1931: Alabamium, Alabamine (Ab). In May 1931 Fred Allison and Edgar J. Murphy, with assistance of Edna R. Bishop and Anna L. Sommer, of the Alabama Polytechnic Institute (Auburn, Ala.) reported that he succeeded in obtaining 0,000002 grams of element #85 in monazite. They named it after the state of Alabama (note). Under this name element #85 figured in textbooks and reference works to 1947. Also mentioned as Alabamium (Am) (note).
• 1937: Dakin (Dacinum?). Searching for a member of the Thorium radioactive family, the chemist Rajendralal De, in Dacca (India, nowadays Bangladesh), found two new elements, the first he named Dakin (Eka-Iodine), the other Gourium (note). It is written that it is named after Dacia, the Roman province in Southeastern Europe, but, seen the discoverer, it is more likely that it is named after Dacca.
• 1939/44 Dor (Do): In 1939 Horia Hulubei (1896-1972) and Yvette Cauchois (1908-1999) observed unknown lines in the emission spectrum of radon, which they attributed to element 85. Hulubei soon announced the discovery but it required many years and hard work before he could complete the spectroscopic identification. Moreover, he had to escape from the Nazi conquest of Paris, then he lost part of his equipment in the fire following the American bombardment of Bucharest on April 15, 1944. In October 1944 he reported: "Now that we have a quasi-certainty that our research and assertions of 1939, on natural elements of atomic number 85 are right, we want to propose a name for this box of the periodic system, that with the case or the confirmation of these experiments would be final and priority of our work officellement allowed. We will decided to call it Dor (Do) this element. The element had been identified for this period of atrocious suffering for humanity. The name would like, by its significance in Rumanian, rappeller a burning desire so that the moment comes where peace will end most odious wars than the history knew". (note).
• 1940: Helvetium (Hv). Suggested by the Swiss physicist Walter Minder (1905-), who observed an extremely weak b decay of RaA. For this purpose he connected a couple of ionisation chambers with an electrometer. Chemical tests confirmed the analogies of this element with iodine. Minder named it, Helvetium, and symbol Hv, after the Latin name for Switzerland. A question of priority arose between him and Hulubei (note).
• 1942: Anglohelvetium (Ah). Minder went on with his researches and two years later, with his colleague, Alice Leigh-Smith, surprisingly repeated the announcement of the discovery of eka-iodine, this time named Anglohelvetium, combination of Anglia (Latin for England) and Helvetia (Latin for Switzerland) (note1) (note2).
• Leptin (from the Greek - weak, unsteady, deprived.

John and Gordon Marks suggested in 1994 the name Therine (Θe) after Thera, the unstable volcanic isle of classical mythology (at present Thira or Santorini). The Marks brothers found the old names ugly and confusing. They offered alternative names that are equivalent contemporary (at the time and place of discovery) metaphors, both more euphonious and more memorable (note).

Further reading:

• Mary Elvira Weeks, "The Discovery of the Elements, XX: Recently Discovered Elements." Journal of Chemical Education 10 (1933), pp. 161-170.
• Mary Elvira Weeks, Discovery of the Elements, comp. rev. by Heny M. Leicester (Easton, Pa.: Journal of Chemical Education, 1968), pp. 837-838.