transuranium

Transuranium refers to the chemical elements that have atomic numbers greater than 92, meaning they lie beyond uranium in the periodic table. The term usually encompasses elements with atomic numbers from 93 to 118, many of which are synthetic and produced only in laboratories.

Most transuranic elements are not found in nature in any significant quantity. They are created by nuclear reactions, typically by bombarding lighter nuclei with neutrons or charged particles in reactors or particle accelerators. Early discoveries in the 1940s and 1950s led to rapid expansion of the group, with new elements named after places, scientists, or mythological figures. Many transuranics exist only for short periods, but a few have isotopes with relatively longer half-lives that enable study and practical uses.

Chemically, transuranics behave mostly like heavy actinides. Their properties often differ from lighter elements due to relativistic effects and complex electron structures, especially for the heavier transactinides. Their radioactivity and toxicity require handling in specialized facilities with strict safety protocols. Research focuses on nuclear structure, chemistry under extreme conditions, and potential applications, though practical use is limited by short lifetimes and safety concerns.

Notable examples include neptunium (93) and plutonium (94), first produced in the early atomic era; americium (95) used in smoke detectors; and californium (98) or einsteinium (99) used as neutron sources in research. The later elements, such as seaborgium, bohrium, and up to oganesson (118), are primarily studied for fundamental science, with most having half-lives measured in milliseconds to days.