Main Page | See live article | Alphabetical index General Name, Symbol, Number Astatine, At, 85 Series Halogens Group, Period, Block 17 (VIIA), 6 , p Density, Hardness no data, no data Appearance metallic Atomic Properties Atomic weight [210] amu Atomic radius no data Covalent radius 127 pm van der Waals radius no data Electron configuration [Xe]44f14 5d10 6s2 6p5 e- 's per energy level 2, 8, 18, 32, 18, 7 Oxidation states (Oxide) ±1,3,5,7 (unknown) Crystal structure no data Physical Properties State of matter solid Melting point 575 K (576 °F) Boiling point no data Molar volume no data Heat of vaporization no data Heat of fusion 114 kJ/mol Vapor pressure no data Speed of sound no data Miscellaneous Electronegativity 2.2 (Pauling scale) Specific heat capacity no data Electrical conductivity no data Thermal conductivity 1.7 W/(m*K) 1st ionization potential 920 kJ/mol (estimated) Most Stable Isotopes iso NA half-life DM DE MeV DP 210At 100% 8.1 h Epsilon Alpha 3.981 5.631 210Po 206Bi SI units & STP are used except where noted. Astatine is a chemical element in the periodic table that has the symbol At and atomic number 85. This radioactive element occurs naturally from uranium and thorium decay and is the heaviest of the halogens. Notable Characteristics This highly radioactive element has been confirmed by mass spectrometers to behave chemically much like other halogens, especially iodine (it probably accumulates in the thyroid gland like iodine). Astatine is thought to be more metallic than iodine. Researchers at the Brookhaven National Laboratory have performed experiments that have identified and measured elementary reactions that involve astatine. The total amount of astatine in Earth's crust is estimated to be less than 1 oz (28 g) at any one time. History Astatine (Greek astatos meaning "unstable") was first synthesized in 1940 by Dale Corson, K. R. MacKenzie, and Emilio Segre of the University of California, Berkeley by barraging bismuth with alpha particles. Occurrence Astatine is produced by bombarding bismuth with energetic alpha particles to obtain relatively long-lived At-209 - At-211, which can then be distilled from the target by heating in the presence of air. Isotopes Astatine has about 20 known isotopes, all of which are radioactive; the longest-lived isotope is 210At which has a half-life of only 8.3 hours. Astatine is a halogen and possibly accumulates in the thyroid like iodine. External Links WebElements.com - Astatine EnvironmentalChemistry.com - Astatine This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.