All transactinide elements are also transuranium elements, that is, have an atomic number greater than that of uranium (92), an actinide. The further distinction of having a greater atomic number than the actinides is significant in several ways:
All of the transactinide elements are radioactive and have only been obtained synthetically in laboratories. None of these elements has ever been collected in a macroscopic sample. Transactinide elements are all named after nuclear physicists and chemists or important locations involved in the synthesis of the elements.
Chemistry Nobelist Glenn T. Seaborg who first proposed the actinide concept which led to the acceptance of the actinide series also proposed the existence of a transactinide series ranging from element 104 to 121 and a superactinide series approximately spanning elements 122 to 153. One of the transactinide elements, Seaborgium, was named in his honor.
The term transactinide is an adjective, and is not commonly used alone as a noun to refer to the transactinide elements.
* The synthesis of these elements has not been officially attested by IUPAC, while in several cases previous syntheses have been confirmed by other institutions or other methods. The names and symbols given are provisional as no names for the elements have been agreed on.