Flerovium
According to the nuclear shell model, the undiscovered neutron-rich nucleus 298Fl may be a doubly magic nucleus, atop the shell closure at N=184. It is predicted that this atom, amid the closed nuclear shells, expected to have longer half-lives for alpha decay and spontaneous fission. However using the fusion-evaporation method to produce this nuclide is impractical, since more neutron-rich starting materials with low proton numbers are unstable due to beta decay.