An artificially produced radioactive element with atomic number 111 that has only been produced in trace amounts. Its most stable known isotope has a mass number of 280 and a half-life of 3.6 seconds. See Periodic Table.
Origin of roentgeniumAfter Wilhelm Conrad Roentgen.
- A transuranic chemical element (symbol Rg) with atomic number 111.
Surname of Wilhelm Roentgen + -ium