Nov. 4, 2011. London, England The General Assembly of the International Union of Pure and Applied Physics (IUPAP) approved the names of the new elements roentgenium (Rg, element 111), as well as two other elements, darmstadtium (Ds, element 110), and copernicium (Cn, element 112).
The new element was created in Darmstadt, Germany at the GSI, the Center for Heavy Ion Research, in 1994, when nine atoms were made. It took another 6 years to produce a second batch. It took fifteen years for the international committee to accept the name of the new element.
Roentgenium contains 111 protons and has an atomic weight of 281, which is the same nominal atomic weight as for darmstadtium, (Ds, 110). It was created by a linear accelerator bombarding bismuth ion targets with nickel ions. (The bismuth atoms have to be stripped of their electrons to overcome the problem of electron cloud coulombic repulsion.) GSI's 120 meter long particle accelerator was used to smash the ions together. Detectors studied the detritus of the after-collision spray of emitted particles, and when it detected . Three atoms (all of the isotope 272Rg) were created in that initial creation process.
The speed of bombardment is crucial. The ballistic ions have to be fast enough to overcome Coulombic repulsion between the positively charged protons in the nuclei of the 'bullets' and the target - but not so fast that the target ions' nuclei are split. Nuclear physicists have prediction models that enable them to predict the range of energies of the ballistic ions that will be able to bind with the target ions' nuclei without splitting them.
The method of nucleus fusion is called "cold fusion". "These are processes which create compound nuclei at low excitation energy (~10–20 MeV, hence "cold"), leading to a higher probability of survival from fission. The excited nucleus then decays to the ground state via the emission of one or two neutrons only."
20983B + 6428Ni → 272111Rg + neutron
(This method has nothing to do with the more widely known Pons & Fleischman cold fusion reaction that caused such a controversy in 1989.)
An international committee consisting of members of IUPAP and IUPAC concluded that the initial report by Hofman, et al, was not sufficient to validate GSI's claim to have created a new element 272111. The IUPAP/IUPAC language is fussy, but that's what science is. In contrast to the case of darmstadtium, where the committee concluded that the work was repeatable and conclusive, this case did not meet with science's high standards. Here is the language of the final report:
"In bombardments of 209Bi targets with 64Ni using the velocity selector SHIP facility to discriminate in favor of the fused product, 273111, three sets of localized alpha-decay chains were observed with position-sensitive detectors. The origin was assigned to the isotope 272111, one neutron removed from the compound nucleus.
"Applying criteria to the case of element 111, the data are of the highest quality. However, there is internal redundancy with just two pairs of data. Chains 2 and 3 have mutually concordant alpha energies, but ones ascribed to the previously unknown 264Bh. Chains 1 and 3 also have mutually concordant alpha energies, but these are ascribed to the previously unknown 268Mt. There is no redundancy involving properties of known daughters for verification purposes.
"Assignment of members of each full chain, unlike the examples of elements 107–109, is burdened by the profuse need to invoke (uncertain) isomeric states with different alpha energies and different lifetimes.
"For example, 272111 decays to two isomeric states of 268Mt; 268Mt decays to two isomeric states of 264Bh; 264Bh possibly decays to two isomeric states of 260Db, only one of which agrees well with the known decay of 260Db. 260Db decays to 256Lr, but the sole observation with a concordant decay energy occurred with a time delay of 66 s. Although statistically consistent with the known mean-life(35 s), the value is arguably sufficiently convincing.
P. J. KAROL et al., © 2001 IUPAC, Pure and Applied Chemistry 73, 959–967, 962
"For chain 1, two of its four alphas have insufficient energy information and the third alpha is of
sufficiently different energy and lifetime compared to chains 2 and 3 to make the sequence assignment
"Chain 2 is most compelling, matching the known 260Db energy and lifetime. Unambiguous observation of its daughter 256Lr in this sequence would have been sufficient to secure the discovery.
"Chain 3 has a mismatch in 260Db’s alpha energy compared to event 2; its daughter appears quite late (66 s) compared to the known 35 s mean-life; and the second full alpha energy (10.221 MeV) disagrees with that of event 2’s second full alpha energy (10.097 MeV).
"JWP ASSESSMENT: The results of this study are definitely of high quality but there is insufficient internal redundancy to warrant certitude at this stage. Confirmation by further results is needed to assign priority of discovery to this collaboration."
GSI repeated the experiment in 2002 and generated another three atoms of Rn. The Joint Working Group (JWG) of IUPAP/IUPAC concluded that the second test was sufficient to validate GSI's claim to have created a new element.
Roentgenium, which had formerly been named unununium (Uu), is a member of Group 11 in the periodic table, along with copper (29Cu), silver (47Ag), and gold (79Au). Too few atoms have been made to test for bulk properties, but Group 11 elements are known for their malleability and high conductivity.
The heavier members of this group are well known for their lack of reactivity or noble character. Silver and gold are both inert to oxygen, but are attacked by the halogens. In addition, silver is attacked by sulfur and hydrogen sulfide, highlighting its higher reactivity compared to gold. Roentgenium is expected to be even more noble than gold and can be expected to be inert to oxygen and halogens. The most-likely reaction is with fluorine to form a trifluoride, RgF3.
Eleven isotopes have been discovered; their half lives range from 26 seconds (281Rg) to 1.6 milliseconds.
God help me. I love science.
Everything2 Writeups: Articles on Chemistry, the Periodic Table, and new elements
- Ford Prefect, Roentgenium, June 2000
- avjewe, Roentgenium, Jun. 2001
- non-buzzard, Periodic Table of the Elements, May, 2002
- rfc1394, Periodic Table of the Elements, Apr, 2001
- Wikipedia, "Roentgenium"
- About.com, "Roentgenium"
- Visual Elements, Roentgenium
- IUPAC, "Element 111 is named roentgenium," press release, Nov. 8, 2011. IUPAC is the International Union of Pure and Applied Chemistry.
- Physics News, "A cluster of Physics News articles on roentgenium," If you're a physics news junkie, and who isn't, you need to keep your eye on Physics News.
- Daniel Cooper, "New periodic table element names confirmed, textbook makers sigh in relief," engadget, Nov. 8, 2011. There's no reason the science news guys can't have a little bit of fun with this.
- Web Elements, "Roentgenium"
- Periodic Table of Videos, "Roentgenium." A YouTube video presented by the University of Nottingham giving history, how Roentgenium was created, properties, etc.
- International Union of Pure and Applied Chemistry, "On the Discovery of the Elements 110-112", IUPAC Technical Report, Pure Appl. Chem., Vol. 73, No. 6, 2001