A fundamental property of the rarest element on Earth, astatine, has been discovered for the first time, scientists say.
Astatine occurs naturally; however, scientists estimate much less than an ounce in total exists worldwide. For a long time, the characteristics of this elusive element were a mystery, but physicists at the CERN physics laboratory in Switzerland have now measured its ionization potential — the amount of energy needed to remove one electron from an atom of astatine, turning it into an ion or a charged particle.
The measurement fills in a missing piece of the periodic table of elements, because astatine was the last naturally occurring element for which this property was unknown. Astatine, which has 85 protons and 85 electrons per atom, is radioactive, and half of its most stable version decays in just 8.1 hours, a time called half-life. In 1953, Isaac Asimov estimated the worldwide total of astatine in nature was 0.002 ounces (0.07 grams).