1s² 2s²p⁶ 3s²p⁶d¹⁰ 4s²p⁶d¹⁰f¹⁴ 5s²p⁶d¹⁰ 6s²p⁵

• History
• Occurrence
• Compounds
• Isotopes
• Astatine Data
• Interactive Periodic Table

History

Researchers at the Brookhaven National Laboratory have performed experiments that have identified and measured elementary reactions that involve Astatine; however, chemical research into Astatine is limited by its extreme rarity, which is a result of its extremely short half-life.

Astatine is the rarest naturally-occurring element, with the total amount in Earth's crust estimated to be less than 1 oz (28 g) at any given time; this amounts to less than one teaspoon of the element.  The Guinness Book of records has dubbed the element the rarest on Earth, stating: "Only around 0.9 oz (25 g) of the element Astatine (At) occurring naturally"; Issac Asimov wrote a 1955 essay on large numbers, scientific notation, and the size of the atom, in which he stated that the number of Astatine atoms on Earth at any time was "only a trillion".

Occurrence

Astatine is produced by bombarding Bismuth with energetic alpha particles to obtain relatively long-lived  ²⁰⁹At - ²¹¹At, which can then be distilled from the target by heating in the presence of air.

Compounds

Multiple compounds of Astatine have been synthesized in microscopic amounts and studied as intensively as possible before their inevitable radioactive disintegration. These compounds are primarily of theoretical interest; however, they are also being studied for potential use in nuclear medicine.

Isotopes

Astatine has 33 known isotopes, all of which are radioactive; the range of their mass numbers is from 191 to 223.  There exist also 23 meta states.  The longest-lived isotope is ²¹⁰At, which has a half-life of 8.1 hours; the shortest-lived known isotope is ²¹³At, which has a half-life of 125 nanoseconds.

(Gr. astatos, unstable) Synthesized in 1940 by D.R. Corson, K.R. MacKenzie, and E. Segre at the University of California by bombarding bismuth with alpha particles.   The longest-lived isotopes, with naturally occurring Uranium and Thorium isotopes, and traces of At-217 are equilibrium with U-233 and Np-239 resulting from interaction of thorium and uranium with naturally produced neutrons.  The total amount of Astatine present in the earth's crust, however, is less than 1 oz.   Astatine can be produced by bombarding Bismuth with energetic alpha particles to obtain the relatively long-lived At-209-211, which can be distilled from the target by heating in air.  The "time of flight" mass spectrometer has been used to confirm that this highly radioactive halogen behaves chemically very much like other halogens, particularly Iodine.   Astatine is said to be more metallic than Iodine, and, like Iodine, it probably accumulates in the thyroid gland.  Workers at the Brookhaven National Laboratory have recently used reactive scattering in crossed molecular beams to identify and measure elementary reactions involving Astatine.

Source: CRC Handbook of Chemistry and Physics, 1913-1995. David R. Lide, Editor in Chief. Author: C.R. Hammond