The Westport Library Resource Guides: Astatine (At): Halogens

What is Astatine?

Astatine (At), radioactive chemical element and the heaviest member of the halogen elements, or Group 17 (VIIa) of the periodic table. Astatine, which has no stable isotopes, was first synthetically produced (1940) at the University of California by American physicists Dale R. Corson, Kenneth R. MacKenzie, and Emilio Segrè, who bombarded bismuth with accelerated alpha particles (helium nuclei) to yield astatine-211 and neutrons. Naturally occurring astatine isotopes have subsequently been found in minute amounts in the three natural radioactive decay series in which they occur by minor branching. Continue reading from Encyclopedia Britannica

The History

In 1939, two groups came near to discovering this element in mineral samples. Horia Hulubei and Yvette Cauchois analysed mineral samples using a high-resolution X-ray apparatus and thought they had detected it. Meanwhile, Walter Minder observed the radioactivity of radium and said it appeared have another element present. He undertook chemical tests which suggested it was like iodine. Element 85 was convincingly produced for the first time at the University of California in 1940 by Dale R. Corson, K.R. Mackenzie, and Emilio Segré. Their astatine was made by bombarding bismuth with alpha particles. Although they reported their discovery, they were unable to carry on with their research due to World War II and the demands of the Manhattan project which diverted all researchers of radioactive materials towards the making of nuclear weapons. Continue reading from Royal Society of Chemistry

Astatine Facts

Astatine is the rarest element on Earth; only approximately 25 grams occur naturally on the planet at any given time. Astatine is the least reactive and has the most metallic properties of any element in the halogen group. The isotope of astatine with the longest half-life is astatine-210 with a half-life of 8.1 hours. Many physical properties of astatine are still unknown, including its color, according to a 2013 article by D. Scott Wilbur published in Nature. Based on the color patterns shown by other members of the halogen family, it is believed that astatine is dark, probably close to black. Continue reading from LiveScience