Beta decay toward minimum mass īeta decay generally causes isotopes to decay toward the isobar with the lowest mass (which is often, but not always, the one with highest binding energy) with the same mass number, those not in italics in the table above. This is a consequence of the fact that a semi-empirical mass formula must consider shell correction and nuclear deformation, which become far more pronounced for heavy nuclides. Beyond the island of stability, various models that correctly predict the known beta-stable isotopes predict anomalies in the beta-stability line that are unobserved in any known nuclides, such as the existence of two beta-stable nuclides with the same odd mass number.
It is widely believed that an island of stability exists along the beta stability line for isotopes of elements around copernicium that are stabilized by shell closures in the region such isotopes would decay primarily through alpha decay or spontaneous fission. The general patterns of beta-stability are expected to continue into the region of superheavy elements, though the exact location of the center of the valley of stability is model dependent. With the exception of 262No, no nuclides with A ≥ 260 have been definitively identified as beta-stable, although 260Fm and 262No are unconfirmed. Īll beta-decay stable nuclides with A ≥ 209 were observed to decay by alpha decay except some where spontaneous fission dominates. Islands of stability are predicted to center near 294Ds and 354126, beyond which the model appears to deviate from several rules of the semi-empirical mass formula. Black denotes the predicted beta-stability line, which is in good agreement with experimental data. One chart of known and predicted nuclides up to Z = 149, N = 256. No beta-decay stable nuclide has proton number 43 or 61 and no beta-decay stable nuclide has neutron number 19, 21, 35, 39, 45, 61, 71, 89, 115, 123, or 147.Īll known beta-decay stable isobars sorted by mass number (This is sometimes dominated by alpha decay or spontaneous fission, especially for the heavy elements.) arrows point towards the lightest-mass isobar. Theoretically predicted or experimentally observed double beta-decay is shown by arrows, i.e.
All elements up to and including nobelium, except technetium and promethium, are known to have at least one beta-stable isotope.ģ50 beta-decay stable nuclides are currently known. Finally, 48Ca and 96Zr have not been observed to undergo beta decay (which is theoretically possible for both), but double beta decay is known for both. Non-primordial 247Cm should undergo beta decay to 247Bk (but has also never been observed to do so). In addition, 123Te and 180mTa have not been observed to decay, but are believed to undergo beta decay with an extremely long half-life (over 10 15 years).