Artificial radioactive element properties unknown	memory peg
	1994 Sigurd Hofmann and co-workers, Darmstadt, Germany
	Wilhelm Conrad Röntgen

First prepared in 1994 by Sigurd Hofmann, Victor Ninov, Fritz Peter Heßberger, Peter Armbruster, H. Folger, Gottfried Münzenberg, H.J. Schött (Gesellschaft für Schwerionenforschung, Darmstadt, Germany), Andre Georgievich Popeko, Alexander Vladimirovich Yeremin, A.N. Andreyev (Лаборатория ядерных реакций им. Г.Н. Флерова / Flerov Laboratory of Nuclear Reactions, FLNR - ОИЯИ / JINR, Дубна (Dubna), Russia), S. Saro, Rudolf Janik (Katedra jadrovej fyziky, Univerzita Komenského, Bratislava, Slovakia), and Matti Leino (Fysiikan laitos, Jyväskylän Yliopisto, Finland).

The new element 111 was produced and unambigously identified in an experiment at SHIP, GSI Darmstadt. In irradiations of ²⁰⁹Bi targets with ⁶⁴Ni projectiles of 318 MeV and 320 MeV three nuclei of the isotope ²⁷²111 were observed. The cross sections are (1.7 +3.3 -1.4) pb and (3.5 +4.6 -2.3) pb, respectively. The nuclei decay by alpha emission into the new and so far heaviest isotopes of the elements 109 and 107 with mass nubers A=268 and A=264. The alpha decay chains were followed down to the known nuclei ²⁶⁰105 and ²⁵⁶Lr.

In 2003 was concluded that the criteria for discovery of an element had been fulfilled this by the collaboration of Hofmann et al. Following this assignment and in accordance with the procedures established by IUPAC for the naming of elements, the discoverers at the GSI were invited to propose a name and symbol. They propose the name roentgenium and the symbol Rg.
This proposal lies within the long established tradition of naming elements to honour famous scientists. Wilhelm Conrad Röntgen (Lennep, Germany 1845-München 1923) discovered X-rays in 1895. Their use has subsequently revolutionised medicine, found wide application in technology and heralded the age of modern physics which is based on atomic and nuclear properties. In 1901 Röntgen was awarded the first Nobel Prize in Physics. The names of the previously discovered elements in row 7 of the Periodic Table also include the names of a series of scientists who have achieved fame in the areas of nuclear chemistry and nuclear physics and this proposal follows that precedent. The Division Committee of the Inorganic Chemistry Division has considered the proposal and recommends to the IUPAC Bureau and Council that the name roentgenium and symbol Rg for element 111 be accepted (Corish & Rosenblatt 2004).
Biography Wilhelm Conrad Röntgen.

Before 2004, the systematic IUPAC name was used (system explained at Ununoctium).

Further reading:

• S. Hofman et al., "The New Element 111." Zeitschrift für Physik A 350 (1995), 281-282 (Submitted December 20, 1994) (Abstract on-line).
• P.J. Karol, H. Nakahara, B.W. Petley, & E. Vogt, On the Discovery of the Elements 110–112 (IUPAC Technical Report). Pure Appl.Chem. 73, 6 (2001), pp.959–967 (PDF file on-line).
• J. Corish and G.M. Rosenblatt, Name and Symbol of the Element with Atomic Number 111 (IUPAC Provisional Recommendation) - Draft 17 May 2004 (PDF file on-iine)