astate

Traductions

• anglais

  Date : 1983

  Définition

  An element. State: solid; group: VIIA; atomic no.: 85; atomic wt.: 211; valence: 1,3,5. Astatine, m.p. 302 °C (576 °F), the heaviest of the halogen elements, is classed as a nonmetal. It occurs in nature in trace quantities, the total in the earth's crust not exceeding 50 grams; thus, its physical properties are not definitely known. All its isotopes are strongly radioactive, the longest-lived having a half life of 8.5 hours. It has no stable form. It is capable of compound formation with other halogens, with oxygen, and with some organic groups. It is a thyroid-seeking element similar to iodine.

  Note :

  Astatine was one of the first elements to be made synthetically (1940) by alpha particle bombardment of bismuth, but the largest quantity made at one time is less than 0.1 microgram.

  Termes :

  1. astatine
  2. At