41. The least stable ground state isotope is astatine -213, with a half-life of 125 nanoseconds. 42. It was formerly known as "'radioactive metal that decays into astatine , radium, and radon. 43. Lighter astatine isotopes have quite high energies of alpha decay, which become lower as the nuclei become heavier. 44. She became provisional director of the institute in 1945 and official in 1947 upon discovering the existence of astatine . 45. The electron affinity of astatine is predicted to be reduced by one-third because of spin-orbit interactions. 46. The most stable isotope is astatine -210, which has a half-life of 8.1 hours. 47. Francium-221 then decays into astatine -217 by alpha decay ( 6.457 MeV decay energy ). 48. There are 32 known isotopes of astatine , with atomic masses ( mass numbers ) of 191 and 193 223. 49. No stable or even long-lived astatine isotope is known, and no such isotope is expected to exist. 50. The least stable ground state isotope is astatine -213, with a half-life of about 125 nanoseconds.
