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Oganesson (118Og) is a synthetic element created in particle accelerators, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first (and so far only) isotope to be synthesized was 294Og in 2002 and 2005; it has a half-life of 0.7 milliseconds. An unconfirmed isotope, 295Og, may have been observed in 2011 with a longer half-life of 181 milliseconds.

Main isotopes of oganesson (118Og)
Iso­tope Decay
abun­dance half-life (t1/2) mode pro­duct
294Og[1] syn 0.7 ms α 290Lv
295Og[2] syn 181 ms? α 291Lv


List of isotopesEdit

Z(p) N(n)  
isotopic mass (u)
half-life decay mode(s) daughter
spin and
294Og 118 176 294.21392(71)# 0.7 ms α 290Lv 0+
SF (various)
295Og[n 1] 118 177 295.21624(69)# 181 ms[2] α 291Lv
  1. ^ Not directly synthesized, occurs in decay chain of 299Ubn; unconfirmed


  • Values marked # are not purely derived from experimental data, but at least partly from systematic trends.
  • Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values from Ame2003 denote one standard deviation. Values from IUPAC are expanded uncertainties.


Theoretical calculations done on the synthetic pathways for, and the half-life of, other isotopes have shown that some could be slightly more stable than the synthesized isotope 294Og, most likely 293Og, 295Og, 296Og, 297Og, 298Og, 300Og and 302Og.[3][4][5] Of these, 297Og might provide the best chances for obtaining longer-lived nuclei,[3][5] and thus might become the focus of future work with this element. Some isotopes with many more neutrons, such as some located around 313Og, could also provide longer-lived nuclei.[6]

Target-projectile combinations leading to Z=118 compound nucleiEdit

The below table contains various combinations of targets and projectiles that could be used to form compound nuclei with Z=118.

Target Projectile CN Attempt result
208Pb 86Kr 294Og* Failure to date
238U 58Fe 296Og* Reaction yet to be attempted
248Cm 50Ti 298Og* Planned reaction
250Cm 50Ti 300Og* Reaction yet to be attempted
249Cf 48Ca 297Og* Successful reaction
250Cf 48Ca 298Og* Failure to date
251Cf 48Ca 299Og* Failure to date
252Cf 48Ca 300Og* Reaction yet to be attempted

Theoretical calculations on evaporation cross sectionsEdit

The below table contains various targets-projectile combinations for which calculations have provided estimates for cross section yields from various neutron evaporation channels. The channel with the highest expected yield is given.

DNS = Di-nuclear system; 2S = Two-step; σ = cross section

Target Projectile CN Channel (product) σ max Model Ref
208Pb 86Kr 294Og 1n (293Og) 0.1 pb DNS [7]
208Pb 85Kr 293Og 1n (292Og) 0.18 pb DNS [7]
246Cm 50Ti 296Og 3n (293Og) 40 fb 2S [8]
244Cm 50Ti 294Og 2n (292Og) 53 fb 2S [8]
252Cf 48Ca 300Og 3n (297Og) 1.2 pb DNS [9]
251Cf 48Ca 299Og 3n (296Og) 1.2 pb DNS [9]
249Cf 48Ca 297Og 3n (294Og) 0.3 pb DNS [9]


  • Isotope masses from:
    • M. Wang; G. Audi; A. H. Wapstra; F. G. Kondev; M. MacCormick; X. Xu; et al. (2012). "The AME2012 atomic mass evaluation (II). Tables, graphs and references" (PDF). Chinese Physics C. 36 (12): 1603–2014. Bibcode:2012ChPhC..36....3M. doi:10.1088/1674-1137/36/12/003.
    • Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
  1. ^ Oganessian, Yu. Ts.; Utyonkov, V. K.; Lobanov, Yu. V.; Abdullin, F. Sh.; Polyakov, A. N.; Sagaidak, R. N.; Shirokovsky, I. V.; Tsyganov, Yu. S.; et al. (2006-10-09). "Synthesis of the isotopes of elements 118 and 116 in the 249Cf and 245Cm+48Ca fusion reactions". Physical Review C. 74 (4): 044602. Bibcode:2006PhRvC..74d4602O. doi:10.1103/PhysRevC.74.044602. Retrieved 2008-01-18.
  2. ^ a b Hofmann, S.; Heinz, S.; Mann, R.; Maurer, J.; Münzenberg, G.; Antalic, S.; Barth, W.; Burkhard, H. G.; Dahl, L.; Eberhardt, K.; Grzywacz, R.; Hamilton, J. H.; Henderson, R. A.; Kenneally, J. M.; Kindler, B.; Kojouharov, I.; Lang, R.; Lommel, B.; Miernik, K.; Miller, D.; Moody, K. J.; Morita, K.; Nishio, K.; Popeko, A. G.; Roberto, J. B.; Runke, J.; Rykaczewski, K. P.; Saro, S.; Schneidenberger, C.; Schött, H. J.; Shaughnessy, D. A.; Stoyer, M. A.; Thörle-Pospiech, P.; Tinschert, K.; Trautmann, N.; Uusitalo, J.; Yeremin, A. V. (2016). "Remarks on the Fission Barriers of SHN and Search for Element 120". In Peninozhkevich, Yu. E.; Sobolev, Yu. G. (eds.). Exotic Nuclei: EXON-2016 Proceedings of the International Symposium on Exotic Nuclei. Exotic Nuclei. pp. 155–164. ISBN 9789813226555.
  3. ^ a b P. Roy Chowdhury; C. Samanta; D. N. Basu (January 26, 2006). "α decay half-lives of new superheavy elements". Physical Review C. 73 (1): 014612. arXiv:nucl-th/0507054. Bibcode:2006PhRvC..73a4612C. doi:10.1103/PhysRevC.73.014612. Retrieved 2008-01-18.
  4. ^ C. Samanta; P. Roy Chowdhury; D. N. Basu (April 6, 2007). "Predictions of alpha decay half lives of heavy and superheavy elements". Nuclear Physics A. 789 (1–4): 142–154. arXiv:nucl-th/0703086. Bibcode:2007NuPhA.789..142S. CiteSeerX doi:10.1016/j.nuclphysa.2007.04.001. Archived from the original on February 1, 2013. Retrieved 2008-01-18.
  5. ^ a b G. Royer; K. Zbiri; C. Bonilla (2004). "Entrance channels and alpha decay half-lives of the heaviest elements". Nuclear Physics A. 730 (3–4): 355–376. arXiv:nucl-th/0410048. Bibcode:2004NuPhA.730..355R. doi:10.1016/j.nuclphysa.2003.11.010. Retrieved 2008-01-18.
  6. ^ S. B. Duarte; O. A. P. Tavares; M. Gonçalves; O. Rodríguez; F. Guzmán; T. N. Barbosa; F. García; A. Dimarco (2004). "Half-life predictions for decay modes of superheavy nuclei". Journal of Physics G: Nuclear and Particle Physics. 30 (10): 1487–1494. Bibcode:2004JPhG...30.1487D. CiteSeerX doi:10.1088/0954-3899/30/10/014. Retrieved 2008-01-18.
  7. ^ a b Feng, Zhao-Qing; Jin, Gen-Ming; Li, Jun-Qing; Scheid, Werner (2007). "Formation of superheavy nuclei in cold fusion reactions". Physical Review C. 76 (4): 044606. arXiv:0707.2588. Bibcode:2007PhRvC..76d4606F. doi:10.1103/PhysRevC.76.044606.
  8. ^ a b Liu, L.; Shen, C.; Li, Q.; Tu, Y.; Wang, X.; Wang, Y. (2016). "Residue cross sections of 50Ti-induced fusion reactions based on the two-step model". European Physical Journal A. 52 (35). arXiv:1512.06504. doi:10.1140/epja/i2016-16035-0.
  9. ^ a b c Feng, Z; Jin, G; Li, J; Scheid, W (2009). "Production of heavy and superheavy nuclei in massive fusion reactions". Nuclear Physics A. 816 (1–4): 33–51. arXiv:0803.1117. Bibcode:2009NuPhA.816...33F. doi:10.1016/j.nuclphysa.2008.11.003.