astatine
Sign in to saveAstatine is a chemical element; it has symbol At and atomic number 85. It is the rarest naturally occurring element in the Earth's crust, occurring only as the decay product of various heavier elements. All of astatine's isotopes are short-lived; the most stable is astatine-210, with a half-life of 8.1 hours. Consequently, a solid sample of the element has never been seen, because any macroscopic specimen would be immediately vaporized by the heat of its radioactivity.
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Astatine is a rare chemical element (symbol At) that exists only as a decay product of heavier elements and has no stable form—all of its isotopes are highly radioactive and short-lived, with the longest-lasting variety lasting only about 8 hours. Because astatine is so radioactive that it instantly vaporizes from its own heat, scientists have never actually observed a solid sample of it, making it one of the most elusive elements on Earth.
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Article
18 sectionsContents
- Characteristics
- Physical
- Chemical
- Compounds
- History
- Isotopes
- Natural occurrence
- Synthesis
- Formation
- Separation methods
- Dry
- Wet
- Uses and precautions
- See also
- Notes
- References
- Bibliography
- External links
Astatine is a chemical element; it has symbol At and atomic number 85. It is the rarest naturally occurring element in the Earth's crust, occurring only as the decay product of various heavier elements. All of astatine's isotopes are short-lived; the most stable is astatine-210, with a half-life of 8.1 hours. Consequently, a solid sample of the element has never been seen, because any macroscopic specimen would be immediately vaporized by the heat of its radioactivity.
The bulk properties of astatine are not known with certainty. Many of them have been estimated from its position on the periodic table as a heavier analog of fluorine, chlorine, bromine, and iodine, the four stable halogens. However, astatine also falls roughly along the dividing line between metals and nonmetals, and some metallic behavior has also been observed and predicted for it. Astatine is likely to have a dark or lustrous appearance and may be a semiconductor or possibly a metal. Chemically, several anionic species of astatine are known and most of its compounds resemble those of iodine, but it also sometimes displays metallic characteristics and shows some similarities to silver.