the road to confirmation of the decay chain of 294Og which has no anchor to known nuclei. For these reasons, other methods of production may need to be researched such as multi-nucleon transfer reactions capable of populating longer-lived nuclei. A similar switch in experimental technique occurred when hot fusion using 48Ca projectiles was used instead of cold fusion (in which cross sections decrease rapidly with increasing atomic number) to populate elements with Z > 113. Nevertheless, several fusion-evaporation reactions leading to unbibium have been proposed in addition to those already tried unsuccessfully, though no institution has immediate plans to make synthesis attempts, instead focusing first on elements 119, 120, and possibly 121. Because cross sections increase with asymmetry of the reaction, a chromium beam would be most favorable in combination with a californium target, especially if the predicted closed neutron shell at N = 184 could be reached in more neutron-rich products and confer additional stability. In particular, the reaction between and would generate the compound nucleus and reach the shell at N = 184, though the analogous reaction with a target is believed to be more feasible because of the presence of unwanted fission products from and difficulty in accumulating the required amount of target material. One possible synthesis of unbibium could occur as follows: + → + 3 Should this reaction be successful and alpha decay remain dominant over spontaneous fission, the resultant 300Ubb would decay through 296Ubn which may be populated in cross-bombardment between 249Cf and 50Ti. Although this reaction is one of the most promising options for the synthesis of unbibium in the near future, the maximum cross section is predicted to be 3 fb, one order of magnitude lower than the lowest measured cross section in a successful reaction. The more symmetrical reactions 244Pu + 64Ni and 248Cm + 58Fe have also been proposed and may produce more neutron-rich isotopes. With increasing atomic number, one must also be aware of decreasing fission barrier heights, resulting in lower survival probability of compound nuclei, especially above the predicted magic numbers at Z = 126 and N = 184. Predicted properties Nuclear stability and isotopes The stability of nuclei decreases greatly with the increase in atomic number after plutonium, the heaviest primordial element, so that all isotopes with an atomic number above 101 decay radioactively with a half-life under a day. No elements with atomic numbers above 82