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The International Union of Pure and Applied Chemistry (IUPAC) has recommended names for elements 114 and 116. Scientists from the Lawrence Livermore National Laboratory (LLNL) and at Dubna proposed the names as Flerovium for element 114 and Livermorium for element 116.
Flerovium (atomic symbol Fl) was chosen to honor Flerov Laboratory of Nuclear Reactions, where superheavy elements, including element 114, were synthesized. Georgiy N. Flerov (1913-1990) was a renowned physicist who discovered the spontaneous fission of uranium and was a pioneer in heavy-ion physics. He is the founder of the Joint Institute for Nuclear Research. In 1991, the laboratory was named after Flerov - Flerov Laboratory of Nuclear Reactions (FLNR).
Livermorium (atomic symbol Lv) was chosen to honor Lawrence Livermore National Laboratory (LLNL) and the city of Livermore, Calif. A group of researchers from the Laboratory, along with scientists at the Flerov Laboratory of Nuclear Reactions, participated in the work carried out in Dubna on the synthesis of superheavy elements, including element 116. (Lawrencium -- Element 103 -- was already named for LLNL's founder E.O. Lawrence.)
In 1989, Flerov and Ken Hulet (1926-2010) of LLNL established collaboration between scientists at LLNL and scientists at FLNR; one of the results of this long-standing collaboration was the synthesis of elements 114 and 116.
The creation of elements 116 and 114 involved smashing calcium ions (with 20 protons each) into a curium target (96 protons) to create element 116. Element 116 decayed almost immediately into element 114. The scientists also created element 114 separately by replacing curium with a plutonium target (94 protons).
The creation of elements 114 and 116 generate hope that the team is on its way to the "island of stability," an area of the periodic table in which new heavy elements would be stable or last long enough for applications to be found.
The new names were submitted to the IUPAC in late October. The new names will not be official until about five months from now when the public comment period is over.
A news reports from IUPAC indicates the confirmation of the discoveries of elements 114 and 116. Proposals for the names of the two elements will follow in due course:
News: Discovery of the Elements with Atomic Number 114 and 116
Priority for the discovery of the elements with atomic number 114 and 116 has been assigned, in accordance with the agreed criteria, to collaborative work between scientists from the Joint Institute for Nuclear Research in Dubna, Russia and from Lawrence Livermore, California, USA (the Dubna-Livermore collaborations). The discovery evidences were recently reviewed and recognized by a IUPAC/IUPAP joint working party. IUPAC confirmed the recognition of the elements in a letter to the leaders of the collaboration.
The IUPAC/IUPAP Joint Working Party (JWP) on the priority of claims to the discovery of new elements has reviewed the relevant literature pertaining to several claims. In accordance with the criteria for the discovery of elements previously established by the 1992 IUPAC/IUPAP Transfermium Working Group, and reiterated by the 1999 and 2003 IUPAC/IUPAP JWPs, it was concluded that “the establishment of the identity of the isotope 283Cn by a large number of decaying chains, originating from a variety of production pathways essentially triangulating its A,Z character enables that nuclide’s use in unequivocally recognizing higher-Z isotopes that are observed to decay through it.” From 2004 Dubna-Livermore collaborations the JWP notes: (i) the internal redundancy and extended decay chain sequence for identification of Z = 287114 from 48Ca + 242Pu fusion (Oganessian et al. Eur. Phys. J. A 19, 3 (2004) and Phys. Rev. C 70, 064609 (2004)); and (ii) that the report of the production of 291116 from the fusion of 48Ca with 245Cm is supported by extended decay chains that include, again, 283Cn and descendants (Oganessian et al. Phys. Rev. C 69, 054607 (2004)). It recommends that the Dubna-Livermore collaborations be credited with discovery of these two new elements.
A full synopsis of the relevant experiments and related efforts is presented in a technical report published online in Pure and Applied Chemistry on 1 June 2011. With the priority for the discovery established, the scientists from the Dubna-Livermore collaborations are invited to propose a name for the two super-heavy elements, elements 114 and 116. The suggested names will then go through a review process before adoption by the IUPAC Council.
Review of the claims associated with elements 113, 115, and 118 are at this time not conclusive and evidences have not met the criteria for discovery.
A paper has just been accepted (5 April 2010) for publication in Physical Review Letters.1
International team discovers element 117
A new chemical element has been added to the Periodic Table: A paper on the discovery of element 117 has been accepted for publication in Physical Review Letters.
Oak Ridge National Laboratory is part of a team that includes the Joint Institute of Nuclear Research (Dubna, Russia), the Research Institute for Advanced Reactors (Dimitrovgrad), Lawrence Livermore National Laboratory, Vanderbilt University and the University of Nevada Las Vegas. ORNL's role included production of the berkelium-249 isotope necessary for the target, which was subjected to an extended, months-long run at the heavy ion accelerator facility at Dubna, Russia.
"Without the berkelium target, there could have been no experiment," says ORNL Director of Strategic Capabilities Jim Roberto, who is a principal author on the PRL paper and who helped initiate the experiment. The berkelium was produced at the High Flux Isotope Reactor and processed at the adjoining Radiochemical Engineering & Development Laboratory as part of the most recent campaign to produce californium-252, a radioisotope widely used in industry and medicine.
"Russia had proposed this experiment in 2004, but since we had no californium production at the time, we couldn't supply the berkelium. With the initiation of californium production in 2008, we were able to implement a collaboration," Roberto says.
Professor Joe Hamilton of Vanderbilt University (who helped establish the Joint Institute for Heavy Ion Research at ORNL) introduced Roberto to Yuri Oganessian of Russia's JINR. Five months of the Dubna JINR U400 accelerator's calcium-48 beam - one of the world's most powerful - was dedicated to the project.
The massive effort identified a total of six atoms of element 117 and the critical reams of data that substantiate their existence.
The two-year experimental campaign began with a 250-day irradiation in HFIR, producing 22 milligrams of berkelium-249, which has a 320-day half-life. The irradiation was followed by 90 days of processing at REDC to separate and purify the berkelium. The Bk-249 target was prepared at Dimitrovgrad and then bombarded for 150 days at the Dubna facility. Lawrence Livermore, which now has been involved in the discovery of six elements with Dubna (113, 114, 115, 116, 117, and 118), contributed data analysis, and the entire team was involved in the assessment of the results.
This is the second element that ORNL has had a role in discovering, joining element 61, promethium, which was discovered at the Graphite Reactor during the Manhattan project and reported in 1946. ORNL, by way of its production of radioisotopes for research, has contributed to the discovery of a total of seven new elements.
Members of the ORNL team include the Physics Division's Krzysztof Rykaczewsi, Porter Bailey of the Nonreactor Nuclear Facilities Division, and Dennis Benker, Julie Ezold, Curtis Porter and Frank Riley of the Nuclear S&T Division. Roberto says the success of the element-117 campaign underscores the value of international collaborations in science.
"This use of ORNL isotopes and Russian accelerators is a tremendous example of the value of working together," he says. "The 117 experiment paired one of the world's leading research reactors--capable of producing the berkelium target material--with the exceptional heavy ion accelerator and detection capabilities at Dubna."
Islands of Stability
Roberto also says the experiment, in addition to discovering a new chemical element, has pushed the Periodic Table further into the neutron-rich regime for heaviest elements. "New isotopes observed in these experiments continue a trend toward higher lifetimes for increased neutron numbers, providing evidence for the proposed "island of stability" for super-heavy nuclei," he says. "Because the half-lives are getting longer, there is potential to study the chemistry of these nuclei," Roberto says. "These experiments and discoveries essentially open new frontiers of chemistry."
The news about the claim was announced in a press release from the Oak Ridge National Laboratory.
- 1. Synthesis of a New Element with Atomic Number Z=117,
, Phys. Rev. Lett., Apr/2010, Volume 104, Number 14, p.142502, (2010)
The discovery of a new chemical element with atomic number Z=117 is reported. The isotopes 293117 and 294117 were produced in fusion reactions between 48Ca and 249Bk. Decay chains involving 11 new nuclei were identified by means of the Dubna gas-filled recoil separator. The measured decay properties show a strong rise of stability for heavier isotopes with Z≥111, validating the concept of the long sought island of enhanced stability for superheavy nuclei.Synthesis of a New Element with Atomic Number Z=117, , Phys. Rev. Lett., Apr/2010, Volume 104, Number 14, p.142502, (2010)
Notes from the 31st meeting of PAC for Nuclear Physics seems to suggest that a claim for element 117 (at the base of the halogen column) may come in the coming weeks and months. It's not very clear which isotopes may have been formed so watch this space.
IV. Experiments on the synthesis of element 117
The PAC heard with great interest the report on the results of the experiment dedicated to the synthesis of element 117 in the 48Ca + 249Bk reaction. The PAC congratulates the staff of the Flerov Laboratory on the discovery of element 117 and new isotopes of elements 115, 113, 111, 109, 107, and 105. The discovery of chains of two neighboring isotopes emphasizes the importance of the odd-even and odd-odd effect for such heavy nuclei. It is in fact especially interesting that the odd-odd chain (3n channel) neighboring to the odd-even chain (4n channel) is twice longer (6 α particles).
It is suggested that poisoning by polonium-210 may have caused the death of Alexander Litvinenko, said to be a former Russian spy, in November 2006. Following his death at the end of November 2006, traces of polonium were found at several places he had visited before becoming ill. Before his death it was thought that thallium, or even radiothallium, might have been the cause of his illness. At the time of writing it is not clear who killed him, but not surprisingly the Russians deny it. Polonium-210 decays through the emission of α-particles and these emissions are noramlly easy to stop, but they are very dangerous if the polonium is inside the body.
Polonium is radioactive and present only in extremely low abundances in the environment. It is quite metallic in nature despite its location beneath oxygen in the periodic table. It is made in very small quantities through a nuclear reaction of bismuth. Neutron irradiation of 209bismuth (atomic number 83) gives 210polonium (atomic number 84).
209Bi + 1n → 210Po + e-
Polonium-210, 210Po, transmutes into the lead isotope 206Pb by the emission of an α-particle. The half life for this process is just over 138 days meaning that after 138 days one-half of the original 210Po has disappeared and after 2 times 138 days 3/4 has gone.
21084Po → 20682Pb + 42He
The short half life of polonium-210 and the heat generated with the above radioactive decay means that polonium metal generates considerable heat (141 W), meaning that the metal and its compounds self-heat. This is a useful property and polonium can be used as a small heat source (if expensive!). It can be used in space satellites for this purpose and is especially desirable as there are no moving parts. It was also used in the lunar rovers to keep internal parts warm during the frigid lunar nights.
Polonium metal is unique in that it is the only element whose structure (known as the α-form) is a simple cubic array of atoms in which each atom is surrounded by six other polonium atoms. On gentle warming to 36°C, this converts into a second form known as the β-form.
Polonium dissolves in acids to form pink hydrated Po(II), presumably as[Po(OH2)6]2+. This seems to oxidize to yellow Po(IV) species perhaps as a consequence of oxidizing agents produced through the α-particle induced decay of water. The polonium(II) oxide PoO is known but this oxidizes easily to the Po(IV) oxide PoO2.
There are few crystallographically characterised polonium compounds largely because not many researchers work with polonium and the difficulties associated with characterising such radioactive compounds. The 14-electron polonium(IV) anion [PoI6]2– is strictly octahedral meaning the lone pair is sterochemically inactive.
Experiments conducted at the Flerov Laboratory of Nuclear Reactions (Joint Institute for Nuclear Research) at Dubna in Russia indicate that element 118 (ununoctium, Uuo) was produced. Not too much though, one atom in the spring of 2002 and two more in 2005.1,2
The 2002 experiment involved firing a beam of 4820Ca at 24998Cf. The experiment took 4 months and involved a beam of 2.5 x 1019 calcium ions to produce the single event believed to be the synthesis of 294118Uuo.
24998Cf + 4820Ca → 294118Uuo + 31n
This ununoctium isotope loses three alpha particles in rapid succesion:
294118Uuo → 290116Uuh + 42He (1.29 milliseconds)
290116Uuh → 286114Uuq + 42He (14.4 milliseconds)
286114Uuq → 282112Uub + 42He (230 milliseconds)
The 282112Uub species then undergoes spontaneous fragmentation (denoted SF) to other species. It took a few years to carry out enough research to properly characterize the decompoition products.
In 2005 a similar experiment but with more sensitive detectors and a total beam dose of 1.6 x 1019 calcium ions resulted in the detection of two further events arising from the formation of 294118Uuo.
This work is particularly significant given the scandal associated with the first report (now withdrawn) of element 118.
- 1. Synthesis of the isotopes of elements 118 and 116 in the Cf249 and Cm245+Ca48 fusion reactions,
, Physical Review C, 10/2006, Volume 74, Issue 4, (2006)
- 2. Synthesis and decay properties of superheavy elements,
, Pure and Applied Chemistry, 2006, Volume 78, Issue 5, p.889 - 904, (2006)
Abstract: A fundamental outcome of modern nuclear theory is the prediction of the "island of stability" in the region of hypothetical superheavy elements. A significant enhancement in nuclear stability at approaching the closed shells with Z = 114 (possibly 120 and 122) and N = 184 is expected for the nuclei with large neutron excess. For this reason, for the synthesis of nuclei with Z = 112-116 and 118, we chose the reactions 238U, 242,244Pu, 243Am, 245,248Cm, and 249Cf + 48Ca, which are characterized by fusion products with a maximal neutron excess. The formation and decay properties of the heaviest nuclei were registered with the use of a gas-filled recoil separator installed at a 48Ca-beam of the heavy-ion cyclotron. The new nuclides mainly undergo sequential α-decay, which ends with spontaneous fission (SF). The total time of decay ranges from 0.5 ms to ~1 d, depending on the proton and neutron numbers in the synthesized nuclei. The atomic number of the new elements 115 and 113 was confirmed also by an independent radiochemical experiment based on the identification of the neutron-rich isotope 268Db (TSF ~ 30 h), the final product in the chain of α-decays of the odd-odd parent nucleus 288115. The comparison of the decay properties of 29 new nuclides with Z = 104-118 and N = 162-177 gives evidence of the decisive influence of the structure of superheavy elements on their stability with respect to different modes of radioactive decay. The investigations connected with the search for superheavy elements in Nature are also presented.Synthesis and decay properties of superheavy elements, , Pure and Applied Chemistry, 2006, Volume 78, Issue 5, p.889 - 904, (2006)
Workers in the USA verify the production of element 114 in the reaction of 244-MeV 48Ca with 242Pu. Two chains of time- and position-correlated decays were assigned to 286114 and 287114. The observed decay modes, half-lives, and decay energies agree with the original claims of researchers at the Joint Institute for Nuclear Research at Dubna in Russia. The Russian results were first reported in 1999. Such independent verification is vital for verification purposes. The measured cross sections at a center-of-target energy of 244 MeV for the 242Pu(48Ca,3–4n)287,286114 reactions were 1.4(+3.2, -1.2) pb each, which are lower than the reported values.1
- 1. Independent Verification of Element 114 Production in the Ca-48 + Pu-242 Reaction,
, Physical Review Letters, Volume 103, Number 13, p.132502, (2009)