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#REDIRECT ] |
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{{Infobox untriseptium}} |
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'''Untriseptium''' ({{IPAc-en|icon|ˌ|uː|n|t|r|aɪ|ˈ|s|ɛ|p|t|i|əm}}), also known as ''']-]'''{{Citation needed|date=February 2012}} or element 137, is a hypothetical ] which has not been observed to occur naturally, nor has it yet been synthesised. Due to ], it is not known if this element is physically possible, as the drip instabilities may imply that the periodic table ends soon after the ] at ]. <ref name=EB>{{cite web|author=Seaborg, G. T.|url=http://www.britannica.com/EBchecked/topic/603220/transuranium-element|title=transuranium element (chemical element)|publisher=Encyclopædia Britannica|date=ca. 2006|accessdate=2010-03-16}}</ref><ref>{{ cite journal|first1=S. |last1=Cwiok|first2= P.-H.|last2= Heenen |first3= W.|last3= Nazarewicz |year=2005|title=Shape coexistence and triaxiality in the superheavy nuclei|journal=Nature|volume=433| page= 705|bibcode = 2005Natur.433..705C |doi = 10.1038/nature03336|issue=7027 |pmid=15716943|pages=705–9}}</ref> Its atomic number is 137 and symbol is Uts. |
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{{Redirect category shell|1= |
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The name ''untriseptium'' is a temporary ] ]. |
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{{R with Wikidata item}} |
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{{R with possibilities}} |
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{{R from subtopic}} |
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{{R adr|Superactinides}} |
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{{R printworthy}} |
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}} |
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] |
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==Synthesis== |
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===Target-projectile combinations leading to Z=137 compound nuclei |
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{|class="wikitable" style="text-align:center" |
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! Target !! Projectile !! CN !! Attempt result |
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!<sup>208</sup>Pb |
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|<sup>137</sup>Cs||<sup>345</sup>Uts||{{unk|Reaction yet to be attempted}} |
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!<sup>209</sup>Bi |
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|<sup>136</sup>Xe||<sup>345</sup>Uts||{{unk|Reaction yet to be attempted}} |
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!<sup>228</sup>Ra |
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|<sup>115</sup>In||<sup>343</sup>Uts||{{unk|Reaction yet to be attempted}} |
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!<sup>227</sup>Ac |
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|<sup>116</sup>Cd||<sup>343</sup>Uts||{{unk|Reaction yet to be attempted}} |
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!<sup>232</sup>Th |
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|<sup>109</sup>Ag||<sup>341</sup>Uts||{{unk|Reaction yet to be attempted}} |
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!<sup>231</sup>Pa |
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|<sup>106</sup>Pd||<sup>337</sup>Uts||{{unk|Reaction yet to be attempted}} |
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!<sup>238</sup>U |
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|<sup>103</sup>Rh||<sup>341</sup>Uts||{{unk|Reaction yet to be attempted}} |
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!<sup>237</sup>Np |
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|<sup>104</sup>Ru||<sup>341</sup>Uts||{{unk|Reaction yet to be attempted}} |
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!<sup>244</sup>Pu |
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|<sup>99</sup>Tc||<sup>343</sup>Uts||{{unk|Reaction yet to be attempted}} |
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!<sup>243</sup>Am |
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|<sup>100</sup>Mo||<sup>343</sup>Uts||{{unk|Reaction yet to be attempted}} |
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!<sup>250</sup>Cm |
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|<sup>93</sup>Nb||<sup>343</sup>Uts||{{unk|Reaction yet to be attempted}} |
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!<sup>249</sup>Bk |
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|<sup>96</sup>Zr||<sup>345</sup>Uts||{{unk|Reaction yet to be attempted}} |
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!<sup>252</sup>Cf |
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|<sup>89</sup>Y||<sup>341</sup>Uts||{{unk|Reaction yet to be attempted}} |
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!<sup>254</sup>Es |
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|<sup>88</sup>Sr||<sup>342</sup>Uts||{{unk|Reaction yet to be attempted}} |
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!<sup>257</sup>Fm |
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|<sup>87</sup>Rb||<sup>344</sup>Uts||{{unk|Reaction yet to be attempted}} |
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!<sup>258</sup>Md |
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|<sup>86</sup>Kr||<sup>344</sup>Uts||{{unk|Reaction yet to be attempted}} |
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!<sup>259</sup>No |
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|<sup>81</sup>Br||<sup>340</sup>Uts||{{unk|Reaction yet to be attempted}} |
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!<sup>262</sup>Lr |
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|<sup>82</sup>Se||<sup>344</sup>Uts||{{unk|Reaction yet to be attempted}} |
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!<sup>267</sup>Rf |
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|<sup>75</sup>As||<sup>342</sup>Uts||{{unk|Reaction yet to be attempted}} |
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!<sup>268</sup>Db |
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|<sup>76</sup>Ge||<sup>344</sup>Uts||{{unk|Reaction yet to be attempted}} |
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!<sup>271</sup>Sg |
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|<sup>71</sup>Ga||<sup>342</sup>Uts||{{unk|Reaction yet to be attempted}} |
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!<sup>274</sup>Bh |
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|<sup>70</sup>Zn||<sup>344</sup>Uts||{{unk|Reaction yet to be attempted}} |
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== Significance == |
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Untriseptium is sometimes called '''feynmanium''' (symbol Fy) because ] noted<ref> |
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{{cite web |
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|first=G.|last= Elert |
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|date= |
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|title=Atomic Models |
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|url=http://physics.info/atomic-models/ |
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|work=The Physics Hypertextbook |
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|accessdate=2009-10-09 |
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}}</ref> that a simplistic interpretation of the ] ] runs into problems with electron orbitals at ''Z'' > 1/α = 137, suggesting that neutral atoms cannot exist beyond untriseptium, and that a periodic table of elements based on electron orbitals therefore breaks down at this point. However, a more rigorous analysis calculates the limit to be ''Z'' ≈ 173.<ref name=Greiner>{{cite journal|author=Walter Greiner and Stefan Schramm|title=Resource Letter QEDV-1: The QED vacuum|journal=American Journal of Physics|volume=76|page=509|year=2008|doi=10.1119/1.2820395|bibcode = 2008AmJPh..76..509G|issue=6 }}, and references therein.</ref> |
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=== Bohr model breakdown {{Anchor|Bohr model}} === |
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The ] exhibits difficulty for atoms with atomic number greater than 137, for the speed of an electron in a ], ''v'', is given by |
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:<math>v = Z \alpha c \approx \frac{Z c}{137.036}</math> |
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where ''Z'' is the ], and ''α'' is the ], a measure of the strength of electromagnetic interactions.<ref>{{cite book |
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|first1=R. |last1=Eisberg|first2= R.|last2= Resnick |
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|year=1985 |
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|title=Quantum Physics of Atoms, Molecules, Solids, Nuclei and Particles |
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|publisher=] |
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|isbn= |
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}}</ref> Under this approximation, any element with an atomic number of greater than 137 would require 1s electrons to be traveling faster than ''c'', the ]. Hence the non-relativistic Bohr model is clearly inaccurate when applied to such an element. |
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=== The Dirac equation === |
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The ] ] also has problems for ''Z'' > 137, for the ground state energy is |
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:<math>E=m c^2 \sqrt{1-Z^2 \alpha^2}</math> |
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where ''m'' is the rest mass of the electron. For ''Z'' > 137, the wave function of the Dirac ground state is oscillatory, rather than bound, and there is no gap between the positive and negative energy spectra, as in the ].<ref> |
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{{cite book |
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|first1=J. D.|last1= Bjorken|first2=S. D.|last2= Drell |
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|year=1964 |
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|title=Relativistic Quantum Mechanics |
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|publisher=] |
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|isbn= |
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}}</ref> |
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More accurate calculations including the effects of the finite size of the nucleus indicate that the binding energy first exceeds 2''mc''<sup>2</sup> for ''Z'' > ''Z''<sub>cr</sub> ≈ 173. For ''Z'' > ''Z''<sub>cr</sub>, if the innermost orbital is not filled, the electric field of the nucleus will pull an electron out of the vacuum, resulting in the ].<ref> |
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{{cite journal |
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|first1=W. |last1=Greiner|first2= S. |last2=Schramm |
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|year=2008 |
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|title=] |
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|volume=76 |pages=509 |
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|doi= |
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}}, and references therein.</ref> |
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==See also== |
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* ] |
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* ] – ] |
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* ] |
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* ] |
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== References == |
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{{Reflist}} |
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{{Compact extended periodic table}} |
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] |
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