The Synthesis of Astatine, At

The element below iodine and between Po and Rn was unknown until D.R. Corson, K.R. Mackenzie and E. Segr‚ synthesized it.

They irradiated bismuth sheets by a particles hoping to increase the atomic number by 2 . They assumed the element be similar to iodine from its position on the periodic table. Thus, they heat the bismuth sheet and the isotopes of astatine sublimated, and condensed on a cold surface.

The reaction releases x = 1, 2, or 3 number of neutrons. In 1940, they made the missing element and called it astatine, At, after the Greek word astatos meaning unstable. Knowing the properties of some astatine isotopes enable the detection of natural astatine isotopes. To date, almost 20 astatine isotopes have discovered with At210 having the longest half-life of 8.3 h.