Characteristics
Astatine is an extremely radioactive element; all its isotopes have half-lives of less than 12 hours, decaying into bismuth, polonium, radon, or other astatine isotopes. Among the first 101 elements in the periodic table, only francium is less stable.
The bulk properties of astatine are not known with any great degree of certainty. Research is limited by its short half-life, which prevents the creation of weighable quantities. A visible piece of astatine would be immediately and completely vaporized due to the heat generated by its intense radioactivity. Astatine is usually classified as either a nonmetal or a metalloid. However, metal formation for condensed-phase astatine has also been suggested.
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