21. Astatine is the rarest naturally occurring element.22. The most important isotope is astatine -211, the only one in commercial use. 23. There are no stable isotopes of astatine . 24. The inclusion of antimony, polonium, and astatine as metalloids also has been questioned. 25. Several authors have commented on the metallic nature of some of the properties of astatine . 26. Additionally, astatine has no stable isotopes. 27. Corson and his colleagues classified astatine as a metal on the basis of its analytical chemistry. 28. All halogens have been observed as diatomic molecules, except for astatine , which is uncertain. 29. According to your web page, the first ionization energy of astatine is 20KJ / mol. 30. Its alpha decay half-life is in accordance : the shortest of all astatine isotopes.
