Unbibium
Unbibium (/[invalid input: 'icon']uːnˈbɪbiəm/), also referred to as eka-thorium or element 122, is the temporary name of a currently unknown chemical element in the periodic table that has the temporary symbol Ubb and the atomic number 122.
| Theoretical element | ||||||
|---|---|---|---|---|---|---|
| Unbibium | ||||||
| Pronunciation | /ˌuːnbaɪˈbaɪəm/ | |||||
| Alternative names | element 122, eka-thorium | |||||
| Unbibium in the periodic table | ||||||
| ||||||
| Atomic number (Z) | 122 | |||||
| Group | g-block groups (no number) | |||||
| Period | period 8 (theoretical, extended table) | |||||
| Block | g-block | |||||
| Electron configuration | predictions vary, see text | |||||
| Physical properties | ||||||
| Phase at STP | unknown | |||||
| Atomic properties | ||||||
| Oxidation states | common: (none) (+4)[1] | |||||
| Ionization energies | ||||||
| Other properties | ||||||
| CAS Number | 54576-73-7 | |||||
| History | ||||||
| Naming | IUPAC systematic element name | |||||
In 2008, it was claimed to have been discovered in natural thorium samples[3] but that claim has now been dismissed by recent repetitions of the experiment using more accurate techniques.
History
തിരുത്തുകNeutron evaporation
തിരുത്തുകThe first attempt to synthesize unbibium was performed in 1972 by Flerov et al. at JINR, using the hot fusion reaction:
No atoms were detected and a yield limit of 5 mb (5,000,000 pb)[dubious ] was measured. Current results (see flerovium) have shown that the sensitivity of this experiment was too low by at least 6 orders of magnitude.[അവലംബം ആവശ്യമാണ്]
In 2000, the Gesellschaft für Schwerionenforschung performed a very similar experiment with much higher sensitivity:
These results indicate that the synthesis of such heavier elements remains a significant challenge and further improvements of beam intensity and experimental efficiency is required. The sensitivity should be increased to 1 fb.[അവലംബം ആവശ്യമാണ്]
Compound nucleus fission
തിരുത്തുകSeveral experiments have been performed between 2000-2004 at the Flerov laboratory of Nuclear Reactions studying the fission characteristics of the compound nucleus 306Ubb. Two nuclear reactions have been used, namely 248Cm + 58Fe and 242Pu + 64Ni. The results have revealed how nuclei such as this fission predominantly by expelling closed shell nuclei such as 132Sn (Z=50, N=82). It was also found that the yield for the fusion-fission pathway was similar between 48Ca and 58Fe projectiles, indicating a possible future use of 58Fe projectiles in superheavy element formation.[4]
Claimed discovery as a naturally occurring element
തിരുത്തുകOn April 24, 2008, a group led by Amnon Marinov at the Hebrew University of Jerusalem claimed to have found single atoms of unbibium in naturally occurring thorium deposits at an abundance of between 10−11 and 10−12, relative to thorium.[3] The claim of Marinov et al. was criticized by a part of the scientific community, and Marinov says he has submitted the article to the journals Nature and Nature Physics but both turned it down without sending it for peer review.[5]
A criticism of the technique, previously used in purportedly identifying lighter thorium isotopes by mass spectrometry,[6][7] was published in Physical Review C in 2008.[8] A rebuttal by the Marinov group was published in Physical Review C after the published comment.[9]
A repeat of the thorium-experiment using the superior method of Accelerator Mass Spectrometry (AMS) failed to confirm the results, despite a 100-fold better sensitivity.[10] This result throws considerable doubt on the results of the Marinov collaboration with regards to their claims of long-lived isotopes of thorium,[6][7] roentgenium[11] and unbibium.[3]
Nucleosynthesis
തിരുത്തുകTarget-projectile combinations leading to Z=122 compound nuclei
തിരുത്തുകThe table below contains various combinations of targets and projectiles which could be used to form compound nuclei with atomic number 122.[അവലംബം ആവശ്യമാണ്]
| Target | Projectile | CN | Attempt result |
|---|---|---|---|
| 238U | 70Zn | 308Ubb | Failure to date |
| 238U | 66Zn | 304Ubb | Failure to date |
| 242Pu | 64Ni | 306Ubb | Failure to date |
| 248Cm | 58Fe | 306Ubb | Failure to date |
Chemical properties
തിരുത്തുകElectronic structure
തിരുത്തുകIt has been predicted by Ephraim Eliav et al. that unbibium will have the electron configuration [Uuo]8s27d18p1.[12]
Extrapolated chemical properties
തിരുത്തുകChemistry
തിരുത്തുകIf group reactivity is followed, unbibium should be a reactive metal, more reactive than cerium or thorium. Unbibium would most likely form the dioxide, UbbO2, and trihalides, such as UbbF3 and UbbCl3. The predicted oxidation states are III and IV (and perhaps II).[അവലംബം ആവശ്യമാണ്]
See also
തിരുത്തുകReferences
തിരുത്തുക- ↑ Pyykkö, Pekka (2011). "A suggested periodic table up to Z ≤ 172, based on Dirac–Fock calculations on atoms and ions". Physical Chemistry Chemical Physics. 13 (1): 161–8. Bibcode:2011PCCP...13..161P. doi:10.1039/c0cp01575j. PMID 20967377.
- ↑ 2.0 2.1 Eliav, E.; Fritzsche, S.; Kaldor, U. (2015). "Electronic structure theory of the superheavy elements". Nuclear Physics A. 944 (December 2015): 518–550. doi:10.1016/j.nuclphysa.2015.06.017.
- ↑ 3.0 3.1 3.2 Marinov, A. (2008). "Evidence for a long-lived superheavy nucleus with atomic mass number A=292 and atomic number Z=~122 in natural Th". International Journal of Modern Physics E. 19: 131. arXiv:0804.3869. Bibcode:2010IJMPE..19..131M. doi:10.1142/S0218301310014662.
{{cite journal}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - ↑ see Flerov lab annual reports 2000–2004 inclusive http://www1.jinr.ru/Reports/Reports_eng_arh.html
- ↑ Royal Society of Chemistry, "Heaviest element claim criticised", Chemical World.
- ↑ 6.0 6.1 A. Marinov; I. Rodushkin; Y. Kashiv; L. Halicz; I. Segal; A. Pape; R. V. Gentry; H. W. Miller; D. Kolb; R. Brandt (2007). "Existence of long-lived isomeric states in naturally-occurring neutron-deficient Th isotopes". Phys. Rev. C. 76 (2): 021303(R). arXiv:nucl-ex/0605008. Bibcode:2007PhRvC..76b1303M. doi:10.1103/PhysRevC.76.021303.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ↑ 7.0 7.1 Marinov, A.; Rodushkin, I.; Kashiv, Y.; Halicz, L.; Segal, I.; Pape, A.; Gentry, R.; Miller, H.; Kolb, D. (2007). "Existence of long-lived isomeric states in naturally-occurring neutron-deficient Th isotopes". Physical Review C. 76 (2): 021303. arXiv:nucl-ex/0605008. Bibcode:2007PhRvC..76b1303M. doi:10.1103/PhysRevC.76.021303.
- ↑ R. C. Barber; J. R. De Laeter (2009). "Comment on "Existence of long-lived isomeric states in naturally-occurring neutron-deficient Th isotopes"". Phys. Rev. C. 79 (4): 049801. Bibcode:2009PhRvC..79d9801B. doi:10.1103/PhysRevC.79.049801.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ↑ A. Marinov; I. Rodushkin; Y. Kashiv; L. Halicz; I. Segal; A. Pape; R. V. Gentry; H. W. Miller; D. Kolb; R. Brandt (2009). "Reply to "Comment on 'Existence of long-lived isomeric states in naturally-occurring neutron-deficient Th isotopes'"". Phys. Rev. C. 79 (4): 049802. Bibcode:2009PhRvC..79d9802M. doi:10.1103/PhysRevC.79.049802.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ↑ J. Lachner; I. Dillmann; T. Faestermann; G. Korschinek; M. Poutivtsev; G. Rugel (2008). "Search for long-lived isomeric states in neutron-deficient thorium isotopes". Phys. Rev. C. 78 (6): 064313. Bibcode:2008PhRvC..78f4313L. doi:10.1103/PhysRevC.78.064313.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ↑ Marinov, A.; Rodushkin, I.; Pape, A.; Kashiv, Y.; Kolb, D.; Brandt, R.; Gentry, R. V.; Miller, H. W.; Halicz, L. (2009). "Existence of Long-Lived Isotopes of a Superheavy Element in Natural Au" (PDF). International Journal of Modern Physics E. 18 (3). World Scientific Publishing Company: 621–629. arXiv:nucl-ex/0702051. Bibcode:2009IJMPE..18..621M. doi:10.1142/S021830130901280X. Retrieved February 12, 2012.
- ↑ Hoffman, Darleane C.; Lee, Diana M.; Pershina, Valeria (2006). "Transactinides and the future elements". In Morss; Edelstein, Norman M.; Fuger, Jean (eds.). The Chemistry of the Actinide and Transactinide Elements (3rd ed.). Dordrecht, The Netherlands: Springer Science+Business Media. p. 1659. ISBN 1-4020-3555-1.