Moscovium is a transactinide element.
In chemistry , transactinide elements -LRB- also , transactinides , or super-heavy elements -RRB- are the chemical elements with atomic numbers from 104 to 120 .. chemistry. chemistry. Their atomic numbers are immediately greater than those of the actinides , the heaviest of which is lawrencium -LRB- atomic number 103 -RRB- .. atomic number. atomic number. lawrencium. lawrencium. Chemistry Nobelist Glenn T. Seaborg first proposed the actinide concept , which led to the acceptance of the actinide series .. actinide. actinide. Glenn T. Seaborg. Glenn T. Seaborg. actinide series. actinide series. He also proposed the transactinide series ranging from element 104 to 121 and the superactinide series approximately spanning elements 122 to 153 .. superactinide series. superactinide series. The transactinide seaborgium was named in his honor .. seaborgium. seaborgium. By definition , transactinide elements are also transuranic elements , i.e. have an atomic number greater than uranium -LRB- 92 -RRB- .. atomic number. atomic number. uranium. uranium. The transactinide elements all have electrons in the 6d subshell in their ground state .. subshell. Electron subshell. Except for rutherfordium and dubnium , even the longest-lasting isotopes of transactinide elements have extremely short half-lives , measured in seconds , or smaller units .. rutherfordium. rutherfordium. dubnium. dubnium. half-lives. half-life. The element naming controversy involved the first five or six transactinide elements .. element naming controversy. Transfermium Wars. These elements thus used systematic names for many years after their discovery had been confirmed .. systematic names. Systematic element name. -LRB- Usually the systematic names are replaced with permanent names proposed by the discoverers relatively shortly after a discovery has been confirmed . -RRB-. systematic names. Systematic element name. Transactinides are radioactive and have only been obtained synthetically in laboratories .. radioactive. radioactive decay. None of these elements has ever been collected in a macroscopic sample .. Transactinide elements are all named after physicists and chemists or important locations involved in the synthesis of the elements .. IUPAC defines an element to exist if its lifetime is longer than 10 − 14 seconds , which is the time it takes for the nucleus to form an electronic cloud .