Periodic Table of the elements main page

Periodic Table

science park

Table of Elements

Chemical information

Science dictionary

scientific data

Site map

Gifts and souvenirs

printable version

go to periodic table










Education Billboard - meet and serve your education needs

Element Fact
Iridium is the most corrosion-resistant metal known. Together with platinum, it is used to make the international prototype of the kilogram, which is the standard definition for the unit of mass.

Astatine, At

astatine sample

Atomic number: 85
Atomic mass: [210] (no stable nuclide)
Natural abundance: -
210At (209.987131) - *%

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.

Physical Data

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)
Density/kgm-3: n/a

Standard Thermodynamic Data (atomic gas)

Enthalpy of formation: -
Gibbs free energy of formation: -
Entropy: -
Heat capacity: -

Electronic data

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

Chemical properties

| Copyright | Privacy | Disclaimer | Contact |

© 2004-2010, all rights reserved.