Ununseptium: Wikis

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ununhexiumUnunseptiumununoctium
At

Uus

(Uhs)
Appearance
Unknown
General properties
Name, symbol, number Ununseptium, Uus, 117
Category notes Unknown
Group, period, block 177, p
Standard atomic weight [294]g·mol−1
Electron configuration Unknown
Electrons per shell 2,8,18,32,32,18,7
(predicted) (Image)
Physical properties
Atomic properties
Miscellanea
CAS registry number 87658-56-8
Most stable isotopes
Main article: Isotopes of Ununseptium
iso NA half-life DM DE (MeV) DP
294Uus syn α 290Uup
293Uus syn α 289Uup

Ununseptium (pronounced /uːnuːnˈsɛptiəm/ ( listen)[1] oon-oon-SEP-tee-əm) is the temporary name of a chemical element with the temporary symbol Uus and atomic number 117. It is the latest element to have been synthesized, having been detected at Dubna in 2009-10.[2] Since it is placed below the halogens it may share qualities similar to astatine or iodine.

Contents

History

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Naming

The element with Z=117 is historically known as eka-astatine (see 'eka' terminology). The name ununseptium is a systematic element name, used as a placeholder until the element is discovered, the discovery is acknowledged by the IUPAC, and the IUPAC decides on a name. Usually, the name suggested by the discoverer(s) is chosen.

According to current guidelines from IUPAC, the ultimate name for all new elements should end in "-ium", which means the name for element 117 may end in -ium, not -ine, even if ununseptium turns out to be a halogen.[3]

Synthesis

The team at the Flerov laboratory of nuclear reactions ran a 7-month-long experiment to synthesize element 117 using the reaction[4]

4820Ca + 24997Bk297117Uus*294117Uus + 310n.

The expected cross-section was of the order of ~2 pb. The expected evaporation residues, 293117 and 294117, were predicted to decay via relatively long decay chains as far as isotopes of dubnium or lawrencium.


Initial reports from Jan 2010 indicate that the neighbouring isotopes 294117 and 293117 were both detected. The heavier isotope decayed by the successive emission of 6 alpha particles down as far as the new isotope 270Db. On the other hand, the lighter odd-even isotope decayed by the emission of just four alpha particles, as far 277Mt, which underwent spontaneous fission. More information on half-lives, decay energies and cross-sections are not yet available.[2]

Future experiments

The team at the GSI in Darmstadt, recently acknowledged as the discoverers of element 112 (see copernicium) have begun experiments aiming towards a synthesis of element 117. The GSI have indicated that if they are unable to acquire any 249Bk from the United States, which is likely given the situation regarding the attempt in Russia, they will study the reaction 244Pu(51V,xn) instead, or possibly 243Am(50Ti,xn).[6]

Isotopes and nuclear properties

Nucleosynthesis

Target-projectile combinations leading to Z=117 compound nuclei

The below table contains various combinations of targets and projectiles which could be used to form compound nuclei with Z=117.

Target Projectile CN Attempt result
208Pb 81Br 289117 Reaction yet to be attempted
232Th 59Co 291117 Reaction yet to be attempted
238U 55Mn 293117 Reaction yet to be attempted
237Np 54Cr 291117 Reaction yet to be attempted
244Pu 51V 295117 Reaction yet to be attempted
243Am 50Ti 293117 Reaction yet to be attempted
248Cm 45Sc 293117 Reaction yet to be attempted
249Bk 48Ca 297117 Successful reaction
249Cf 41K 290117 Reaction yet to be attempted

Chronology of isotope discovery

Isotope Year discovered Discovery reaction
294Uus 2009 249Bk(48Ca,3n)
293Uus 2009 249Bk(48Ca,4n)

Theoretical calculations

Evaporation residue cross sections

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; σ = cross section

Target Projectile CN Channel (product) σmax Model Ref
209Bi 82Se 291117 1n (290117) 15 fb DNS [7]
209Bi 79Se 288117 1n (287117) 0.2 pb DNS [7]
232Th 59Co 291117 2n (289117) 0.1 pb DNS [7]
238U 55Mn 293117 2-3n (291,290117) 70 fb DNS [7]
244Pu 51V 295117 3n (292117) 0.6 pb DNS [7]
248Cm 45Sc 293117 4n (289117) 2.9 pb DNS [7]
246Cm 45Sc 291117 4n (287117) 1 pb DNS [7]
249Bk 48Ca 297117 3n (294117) 2.1 pb ; 3 pb DNS [7][8]
247Bk 48Ca 295117 3n (292117) 0.8, 0.9 pb DNS [8][7]

Decay characteristics

Theoretical calculations in a quantum tunneling model with mass estimates from a macroscopic-microscopic model predict the alpha-decay half-lives of isotopes of the element 117 (namely, 289-303117) to be around 0.1–40 ms.[9][10][11]

Chemical properties

Predicted chemical properties

Certain chemical properties, such as bond lengths, are predicted to differ from what one would expect based on periodic trends from the lighter halogens (because of relativistic effects). It may have some metalloid properties, like astatine.[12]

References

  1. ^ J. Chatt (1979). "Recommendations for the Naming of Elements of Atomic Numbers Greater than 100". Pure Appl. Chem. 51: 381–384. doi:10.1351/pac197951020381. 
  2. ^ a b http://www.jinr.ru/img_sections/PAC/NP/31/PAK_NP_31_recom_eng.pdf
  3. ^ Koppenol, W. H. (2002). "Naming of new elements(IUPAC Recommendations 2002)". Pure and Applied Chemistry 74: 787. doi:10.1351/pac200274050787. http://media.iupac.org/publications/pac/2002/pdf/7405x0787.pdf. 
  4. ^ Flerov Lab.
  5. ^ a b sagaidak. "Experiment setting on synthesis of superheavy nuclei in fusion-evaporation reactions. Preparation to synthesis of new element with Z=117". http://159.93.28.88/linkc/education/SHE_Sagaidak.pdf. Retrieved 2009-07-07. 
  6. ^ Toward element 117
  7. ^ a b c d e f g h i Zhao-Qing, Feng (2007). "Possible Way to Synthesize Superheavy Element Z = 117". Chinese Physics Letters 24: 2551. doi:10.1088/0256-307X/24/9/024. http://arxiv.org/pdf/0708.0159. 
  8. ^ a b Feng, Z (2009). "Production of heavy and superheavy nuclei in massive fusion reactions". Nuclear Physics A 816: 33. doi:10.1016/j.nuclphysa.2008.11.003. http://arxiv.org/pdf/0803.1117. 
  9. ^ C. Samanta, P. Roy Chowdhury and D.N. Basu (2007). "Predictions of alpha decay half lives of heavy and superheavy elements". Nucl. Phys. A 789: 142. doi:10.1016/j.nuclphysa.2007.04.001. 
  10. ^ P. Roy Chowdhury, C. Samanta, and D. N. Basu (2008). "Search for long lived heaviest nuclei beyond the valley of stability". Phys. Rev. C 77: 044603. doi:10.1103/PhysRevC.77.044603. 
  11. ^ P. Roy Chowdhury, C. Samanta, and D. N. Basu (2008). "Nuclear half-lives for α -radioactivity of elements with 100 ≤ Z ≤ 130". At. Data & Nucl. Data Tables 94: 781–806. doi:10.1016/j.adt.2008.01.003. 
  12. ^ Trond Saue. "Principles and Applications of Relativistic Molecular Calculations". http://dirac.chem.sdu.dk/thesis/96.saue_phd.pdf. , page 76

Wiktionary

Up to date as of January 15, 2010

Definition from Wiktionary, a free dictionary

See also ununseptium

German

Chemical Element: Uuh (atomic number 117)

Noun

Ununseptium n

  1. ununseptium

Simple English

Ununseptium is the temporary name of a chemical element. It has not been discovered. It has the temporary symbol Uus. The element would have the atomic number 117. Ununseptium can also be named eka-astatine.

History

Ununseptium was discovered in 2009-10. 6 atoms were detected.

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