transactinides

Transactinides are the chemical elements with atomic numbers 104 through 118, the elements beyond the actinide series. All transactinides are synthetic and highly radioactive; none occur naturally. They are produced in particle accelerators by fusion-evaporation reactions, typically by bombarding actinide targets with ion beams such as carbon, nitrogen, neon, or helium. The first successful syntheses occurred in the late 20th century through experiments in Soviet and American laboratories; subsequent work at facilities in Dubna, Livermore, and other centers expanded the series.

Most transactinides have very short half-lives, typically from milliseconds to seconds, with their nuclei decaying by alpha emission or spontaneous fission. Because of their fleeting existence, detailed chemical tests are limited to a handful of elements and isotopes, often using rapid separation methods to study their behavior before decay.

Chemically, transactinide elements are expected to follow trends on the periodic table but relativistic effects can modify properties, particularly for the heaviest members. Rutherfordium and seaborgium have shown chemistry similar to their lighter homologs in limited experiments; for nihonium, moscovium, tennessine, and oganesson, only scant data exist, and oganesson may challenge the notion of a noble gas at the bottom of the table.

Most transactinides have no practical applications outside basic science; research focuses on nuclear physics, synthesis methods, and exploring chemical properties of superheavy elements. The names reflect discoverers or locations, such as rutherfordium (Rf), dubnium (Db), copernicium (Cn), nihonium (Nh), flerovium (Fl), moscovium (Mc), livermorium (Lv), tennessine (Ts), and oganesson (Og).