superheavy

Superheavy elements (SHE) are chemical elements with very high atomic numbers, typically Z ≥ 104. They are all synthetic and do not occur naturally, existing only for very short times before decaying. The study of SHE probes the limits of nuclear stability and the structure of the atomic nucleus.

Most SHE have been produced in particle accelerators by fusing lighter nuclei in a process known as nuclear fusion. The most successful approach, often called hot fusion, uses a calcium-48 beam directed at actinide targets (such as plutonium, curium, or berkelium). The resulting compound nucleus may survive long enough to emit one or more neutrons and then decay by alpha emission or fission. Production rates are tiny—often only a few atoms per week.

Many SHE are highly unstable; their short lifetimes reflect strong Coulomb repulsion among the many protons in the nucleus. Theoretical models predict a region of relatively longer-lived nuclei, the island of stability, around Z ≈ 114–126 and N ≈ 184, though empirical confirmation remains limited.

Relativistic effects on the motion of electrons are expected to alter their chemistry, causing deviations from periodic trends observed in lighter elements. Some predictions suggest that at the very end of the periodic table, elements may exhibit unusual or unexpected behavior; for example, oganesson (118) is predicted to be a noble gas with unusually low reactivity, while others may display metal-like characteristics.

The first superheavy elements to be confirmed were discovered in the late 1960s to the 1990s; elements 104–118 have been observed and named. Research continues at large accelerator facilities around the world. Because of their extremely short lifetimes, SHE have no practical applications beyond advancing fundamental science, nuclear theory, and our understanding of chemical periodicity.