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Numero Atomico 85

The History and Properties of Element 85: Astatine

The Rarest Naturally Occurring Element

Astatine, the element with atomic number 85, is a radioactive metalloid that is the rarest naturally occurring element on Earth. It is found in trace amounts in uranium ores and is produced artificially through nuclear reactions. Astatine is a member of the halogen group and has similar properties to other halogens like chlorine and iodine. It is a highly reactive element that forms salts with metals and is used in various scientific applications.

Discovery and Natural Occurrence

Astatine was first discovered in 1940 by Dale R. Corson, Kenneth Ross MacKenzie, and Emilio Segrè at the University of California, Berkeley. They bombarded bismuth-209 with alpha particles, which resulted in the formation of astatine-211. Astatine is not found in significant concentrations naturally because it is a decay product of other radioactive elements, particularly uranium and thorium. It has 33 known isotopes, all of which are radioactive, with the longest-lived isotope being astatine-210, which has a half-life of 8.1 hours.

Chemical Properties and Uses

As a halogen, astatine has a high affinity for electrons and is a powerful oxidizing agent. It reacts readily with other elements, including metals and non-metals. Astatine forms salts with alkali metals, alkaline earth metals, and transition metals. It is also known to form interhalogen compounds with other halogens. Due to its high radioactivity, astatine has limited practical applications. However, its isotopes have been used in scientific research, particularly in the fields of nuclear medicine and radiochemistry.

Interesting Facts

* Astatine is the heaviest halogen and the ninth-densest element on the periodic table. * It is estimated that there are less than 30 grams of astatine in the Earth's crust. * The name “astatine” is derived from the Greek word “astatos,” which means “unstable,” referring to the element's highly radioactive nature. * Astatine is the only element that is not found in the Earth's crust but has been detected in other celestial bodies, such as the Moon and some meteorites. * The most stable isotope of astatine, astatine-210, has a half-life of only 8.1 hours. This means that it decays into other elements relatively quickly.

Conclusion

Astatine is a rare and fascinating element with unique properties. Its high radioactivity limits its practical applications, but it has been used in scientific research and has provided valuable insights into the nature of matter. As technology advances, new discoveries about astatine's properties and potential uses may emerge.