Astatine is a chemical element with the symbol At and atomic number 85. It is the rarest naturally occurring element in the Earth’s crust, occurring only as of the decay product of various heavier elements. It is a radioactive element and is said to be the most heavier among the halogens. This element exhibits similar chemical properties that of the element iodine. It has about seven isotopes. This element appears as a black solid with a metallic look.
|Oxidation states||−1, +1, +3(?), +5, +7(?)|
Astatine is likely to have a dark or lustrous appearance and maybe a semiconductor or possibly a metal; it probably has a higher melting point than that of iodine. Chemically, several anionic species of astatine are known and most of its compounds resemble those of iodine. It also shows some metallic behavior, including being able to form a stable monatomic cation in aqueous solution, unlike the lighter halogens.
Physical and Chemical Properties of Astatine
- It is an extremely radioactive element; all its isotopes have half-lives of 8.1 hours or less, decaying into other astatine isotopes, bismuth, polonium, or radon.
- The bulk properties of At are not known with any certainty.
- Research is limited by its short half-life, which prevents the creation of weighable quantities.