History and Production
From Greek astatos, meaning unstable. It was first made by D.R. Corson, K.R. Mackenzie and E. Segré in 1940. They synthesized the isotope 211At by bombardment of 209Bi with a-particle in a cyclotron at the University of California.
There is no commercial use of the element except for research interests. Until around 1999, only about 0.05 mg has been prepared.
Bulk physical properties of the element is not known due to short half-life of all isotopes. The longest half-life is only 8.3 hour for 210At. From limited experimental evidence, astatine may behave chemically similar to iodine. It is also perhaps the rarest natural occurring terrestrial element with no more than 44 mg of the element on the first kilometer of the earth's crust.
It may exist with natural occurring uranium and thorium isotopes.
Interatomic distance: 290 pm (covalent bond diameter)
Melting point: 300°C (est.)
Boiling point: 337°C (est.)
Thermal conductivity/Wm-1K-1: 1.7 (27°C)
Standard Thermodynamic Data (atomic gas)
Enthalpy of formation: -
Gibbs free energy of formation: -
Heat capacity: -
Electronic configuration: [Xe] 4f14 5d10 6s2 6p5
Term symbol: 3P3/2
Electron affinity: 270.1591 kJ/mol Electronegativity (Pauline): 2.20
Ionization energy (first, second, third): 930, 1600, - kJ/mol