Term: astatine (At)
Literally meaning: “pertaining to unstable”
The element named after observation that there are no stable astatine isotopes as the longest lived isotope (astatine-210) has a half –life of 8.3 hours.
For many years scientists had noticed that in Mendeleev published periodic table was a space underneath iodine known theoretically as eka-iodine but no one could identified in nature this element. In 1940, finally, the element was detected and produced by Americans physicts D.R Corson(1914-2012), K R Mackenzie (1912-2002), E Segre (1905-1989) in California by bombarding bismuth-209 with alpha particles in a cyclotron.
Astatine is a chemical element with atomic number 85 and atomic mass 210. Astatine is highly radioactive and is only available in tiny quantities with no significant influence in biosphere.