The alpha-decay half-lives predicted for 291–307Uue are on the order of microseconds. The longest alpha-decay half-life predicted is ~485 microseconds for the isotope 294Uue. When factoring in all decay modes, the predicted half-lives drop further to only tens of microseconds. Some heavier isotopes may be more stable; Fricke and Waber predicted 315Uue to be the most stable ununennium isotope in 1971. This has consequences for the synthesis of ununennium, as isotopes with half-lives below one microsecond would decay before reaching the detector, and the heavier isotopes cannot be synthesised by the collision of any known usable target and projectile nuclei. Nevertheless, new theoretical models show that the expected gap in energy between the proton orbitals 2f7/2 (filled at element 114) and 2f5/2 (filled at element 120) is smaller than expected, so that element 114 no longer appears to be a stable spherical closed nuclear shell, and this energy gap may increase the stability of elements 119 and 120. The next doubly magic nucleus is now expected to be around the spherical 306Ubb (element 122), but the expected low half-life and low production cross section of this nuclide makes its synthesis challenging.
The alpha-decay half-lives predicted for 291–307Uue are on the order of microseconds The longest alpha-decay half-life predicted is ~485 microseconds for the isotope 294Uue When factoring in all decay modes the predicted half-lives drop further to only tens of microseconds Some heavier isotopes may be more stable; Fricke and Waber predicted 315Uue to be the most stable ununennium isotope in 1971 This has consequences for the synthesis of ununennium as isotopes with half-lives below one microsecond would decay before reaching the detector and the heavier isotopes cannot be synthesised by the collision of any known usable target and projectile nuclei Nevertheless new theoretical models show that the expected gap in energy between the proton orbitals 2f7/2 (filled at element 114) and 2f5/2 (filled at element 120) is smaller than expected so that element 114 no longer appears to be a stable spherical closed nuclear shell and this energy gap may increase the stability of elements 119 and 120 The next doubly magic nucleus is now expected to be around the spherical 306Ubb (element 122) but the expected low half-life and low production cross section of this nuclide makes its synthesis challenging