astatine




 * By: Johnny Wang, Nhi Huynh, Miuki Gwaltney, Tasha Diehl**
 * Edited by: Leo Andrews**
 * Atomic Num****ber: 85**
 * Atomic Weight:** 210
 * Melting Point:** 575 K (302 C or 576 F)
 * Density:** About 7 grams per cubic centimeter
 * Boiling Point:** 613 K (340 C or 644 C)
 * Phase at Room Temperature:** Solid

Astatine occurs in vanishingly small quantities in the natural decay chains of uranium and thorium minerals.
 * Element Classification:** Metalloid (sometimes classified as a halogen)

Astatine was produced by Dale R. Carson, K.R. MacKenzie and Emilio Segrè by bombarding an isotope of bismuth, bismuth-209, with alpha particles that had been accelerated in a device called a cyclotron. This created astatine-211 and two free neutrons. Small amounts of astatine exist in nature as a result of the decay of uranium and thorium, although the total amount of astatine in the earth's crust at any particular time is less than 30 grams. Due to its scarcity, astatine is produced when it is needed and occurs in extremely small quantities. A total of 0.05 micrograms (0.00000005 grams) of astatine have been produced to date. Astatine's most stable isotope, astatine-210, has a half-life of 8.1 hours. It decays into bismuth-206 through alpha decay or into polonium-210 through electron capture. Astatine-211 is being used in nuclear medicine for targeted alpha particle radiotherapy against compartmental tumors.
 * History and Uses:**


 * Facts:**
 * Astatine cannot be seen with the naked eye, since a large enough sample would immediately disintegrate due to its own radioactivity.
 * Astatine is the rarest element on Earth
 * Isotope At-211 is used in the diagnosis of some diseases
 * Astatine has an important use in nuclear medicine, but it must be treated diligently because of its short half-life
 * There are 32 isotopes of astatine, all of which are extremely radioactive