Physics of Superheavy Nuclei

Where does the Periodic Table end? What is the mass of the heaviest atomic nucleus? With the addition of four new elements in 2015, the seventh row of the table is now complete, but answers to such basic questions remain elusive. I will present a brief review of the current status of the topic, and recent controversies in the field, including the failure to directly determine the atomic number, Z, and mass number, A, of many of the newly discovered superheavy isotopes. Then I will turn to describing new efforts to address outstanding issues. For instance, while the single-particle structure is vital to understanding the stability of the heaviest elements, the alpha decay and fission processes ultimately determine how long a nucleus will survive. Recent observations, and theoretical descriptions, suggest that metastable states, which can have substantial hindrance to fission and favor decay via alpha emission, may be much longer lived than the ground state of the same nucleus. Such results have tremendous implications for how far we may be able to push the experimental studies of the heaviest elements.