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A '''period 9 element''' is any one of 8 hypothetical ]s (unhexpentium through unseptbium) belonging to a ninth ] of the ]. They may be referred to using ] ]s. None of these elements have been ],<ref group="note">The heaviest element that has been synthesized to date is ] with atomic number 118, which is the last ].</ref> and it is possible that none have isotopes with stable enough nuclei to receive significant attention in the near future. It is also possible that, due to ], none of the period 9 elements are physically possible and the periodic table may end soon after the ] at ] with atomic number 126.<ref name="emsley">{{cite book|last=Emsley|first=John|title=Nature's Building Blocks: An A-Z Guide to the Elements|edition=New|year=2011|publisher=Oxford University Press|location=New York, NY|isbn=978-0-19-960563-7}}</ref>{{Rp|593|date=November 2012}} The names given to these unattested elements are all ]. In contrast to periods ] through ], the ninth period of the periodic table is expected to lack any ]s, and is expected to be analogous to the ] and ] periods. |
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==History== |
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There are currently seven ]s in the ] of ], culminating with ] 118. If further elements with higher atomic numbers than this are discovered, they will be placed in additional periods, laid out (as with the existing periods) to illustrate periodically recurring trends in the properties of the elements concerned. Any additional periods are expected to contain a larger number of elements than the seventh period, as they are calculated to contain elements with filled g-]s in their ground state. An eight-period table containing these elements was suggested by ] in 1969.<ref name="LBNL">{{ cite web |url=http://www.lbl.gov/LBL-PID/Nobelists/Seaborg/65th-anniv/29.html |title= An Early History of LBNL |first=Glenn |last=Seaborg |date=August 26, 1996}}</ref><ref>{{cite journal | doi = 10.2307/3963006 | last1 = Frazier | first1 = K. | title = Superheavy Elements | journal = Science News | volume = 113 | issue = 15 | pages = 236–238 | year = 1978 | jstor = 3963006}}</ref> No elements in this region have been synthesized or discovered in nature. While Seaborg's version of the extended period had the heavier elements following the pattern set by lighter elements, as it did not take into account ], models that take relativistic effects into account do not. ] and B. Fricke used computer modeling to calculate the positions of elements up to '']'' = 172 (comprising periods 8 and 9), and found that several were displaced from the ].<ref name="rsc.org">{{Cite web |url=http://www.rsc.org/Publishing/ChemScience/Volume/2010/11/Extended_elements.asp |title=Extended elements: new periodic table |year=2010}}</ref><ref name="Fricke">{{cite journal |last1=Fricke |first1=B. |last2=Greiner |first2=W. |last3=Waber |first3=J. T. |year=1971 |title=The continuation of the periodic table up to Z = 172. The chemistry of superheavy elements |journal=Theoretica chimica acta |volume=21 |issue=3 |pages=235–260 |publisher=Springer-Verlag |doi=10.1007/BF01172015 |url=http://link.springer.com/article/10.1007%2FBF01172015?LI=true# |accessdate=28 November 2012}}</ref> Fricke predicted the structure of the extended periodic table up to ''Z'' = 172 to be: |
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{{Compact extended periodic table}} |
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] |
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==Predicted properties== |
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===Chemical and physical properties=== |
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Period 9 should begin with elements 165 (unhexpentium) and 166 (unhexhexium), which should be normal ] and ]s. The 9s electrons should have ionization energies comparable to those of the 3s electrons of ] and ], due to relativistic effects causing the 9s electrons to be much more strongly bound than non-relativistic calculations would predict. Elements 165 and 166 should mostly exhibit the +1 and +2 oxidation states respectively; however, the ionization energies of the 7d electrons are low enough to possibly allow higher oxidation states like +3 and +4 to occur.<ref name=Fricke/><ref name=Haire>{{cite book| title = The Chemistry of the Actinide and Transactinide Elements| editor1-last = Morss|editor2-first = Norman M.| editor2-last = Edelstein| editor3-last = Fuger|editor3-first = Jean| last = Haire|first = Richard G.| chapter = Transactinides and the future elements| publisher = ]| year = 2006| isbn = 1-4020-3555-1| location = Dordrecht, The Netherlands| edition = 3rd| ref = CITEREFHaire2006}}</ref> |
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In elements 167 to 172, the 9p<sub>1/2</sub> and 8p<sub>3/2</sub> shells will be filled. Their energy ]s are so close together that they behaves as one combined ''p'' shell, similar to the non-relativistic 2p and 3p shells. Thus, the ] does not occur and the most common oxidation states of elements 167 to 170 should be +3, +4, +5, and +6 respectively. Element 171 (unseptunium) is expected to be a ], showing various oxidation states ranging from –1 to +7. Its electron affinity should be 3.0 ], allowing it to form a hydride, UsuH. Element 172 (unseptbium) should be a ] with chemical behaviour similar to that of ], as their ionization energies should be very similar. The only main difference between them is that element 172, unlike xenon, is expected to be a ] or a ] due to its much higher atomic weight.<ref name=Fricke/> |
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<div style="float: center; margin: 1px; font-size:85%;"> |
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:{| class="wikitable sortable" |
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|+ Some predicted properties of the period 9 elements. The metallic radii and densities are first approximations.<ref name="Fricke"/><ref name="Haire"/> |
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! Property |
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! 165 |
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! 166 |
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! 167 |
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! 168 |
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! 169 |
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! 170 |
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! 171 |
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! 172 |
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! ] |
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! ] |
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| ] |
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| ] |
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| ] |
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| ] |
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| ] |
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| ] |
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! Valence ] |
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| 9s<sup>1</sup> |
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| 9s<sup>2</sup> |
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| 9s<sup>2</sup> 9p<sup>1</sup> |
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| 9s<sup>2</sup> 9p<sup>2</sup> |
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| 9s<sup>2</sup> 9p<sup>2</sup> 8p<sup>1</sup> |
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| 9s<sup>2</sup> 9p<sup>2</sup> 8p<sup>2</sup> |
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| 9s<sup>2</sup> 9p<sup>2</sup> 8p<sup>3</sup> |
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| 9s<sup>2</sup> 9p<sup>2</sup> 8p<sup>4</sup> |
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! Stable ]s |
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| 1 |
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| 2 |
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| 3 |
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| 4 |
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| 5 |
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| 6 |
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| −1, 3, 7 |
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| 0, 4, 6, 8 |
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! First ] |
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| 521.0 kJ/mol |
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| 627.2 kJ/mol |
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| 617.5 kJ/mol |
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| 723.6 kJ/mol |
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| 800.8 kJ/mol |
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| 887.7 kJ/mol |
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| 984.2 kJ/mol |
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| 1090.3 kJ/mol |
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! ] or ] |
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| 250 pm |
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| 200 pm |
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| 190 pm |
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| 180 pm |
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| 175 pm |
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| 170 pm |
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| 165 pm |
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| 220 pm |
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! ] |
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| 7 g/cm<sup>3</sup> |
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| 11 g/cm<sup>3</sup> |
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| 17 g/cm<sup>3</sup> |
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| 19 g/cm<sup>3</sup> |
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| 18 g/cm<sup>3</sup> |
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| 17 g/cm<sup>3</sup> |
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| 16 g/cm<sup>3</sup> |
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| 9 g/cm<sup>3</sup> |
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</div> |
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===Nuclear properties=== |
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{{empty section|date=December 2012}} |
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<!--we should write about further elements and the eka-superactinides--> |
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==See also== |
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* ] |
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* ] |
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* ] |
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==Notes== |
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{{reflist|group=note}} |
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==References== |
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{{reflist}} |
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<!-- footers --> |
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{{PeriodicTablesFooter}} |
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{{Compact extended periodic table}} |
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{{DEFAULTSORT:Period 9 Element}} |
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