Yttrium one stable isotope, Y, which is also the only isotope that occurs naturally. However, the lanthanide rare earths contain elements of even atomic number and many stable isotopes. Yttrium-89 is thought to be more abundant than it otherwise would be, due in part to the s-process, which allows enough time for isotopes created by other processes to decay by electron emission (neutron → proton). Such a slow process tends to favor isotopes with atomic mass numbers (A = protons + neutrons) around 90, 138 and 208, which have unusually stable atomic nuclei with 50, 82, and 126 neutrons, respectively. Y
Otto Hahn pupil and assistant Fritz Strassmann (1902–1980), Otto Hahn furthered the research begun by Enrico Fermi and his team in 1934 when they bombarded uranium with neutrons. Until 1938, it was believed that the elements with atomic numbers greater than 92 (known as transuranium elements) arose when uranium atoms were bombarded with neutrons. The German chemist Ida Noddack proposed an exception. She anticipated the paradigm shift of 1938/39 in her article published in the journal "Angewandte Chemie", Nr. 47, 1934, in which she speculated: It is conceivable that when heavy nuclei are bombarded with neutrons these nuclei could break down into