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User:Kepler-1229b/Uts/Infobox untriseptium Untriseptium (/ˌntrˈsɛptiəm/), also known as eka-dubnium[citation needed] or element 137, is a hypothetical chemical element which has not been observed to occur naturally, nor has it yet been synthesised. Due to drip instabilities, it is not known if this element is physically possible, as the drip instabilities may imply that the periodic table ends soon after the island of stability at unbihexium. [1][2] Its atomic number is 137 and symbol is Uts.

The name untriseptium is a temporary IUPAC systematic element name.

Synthesis

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Target-projectile combinations leading to Z=137 compound nuclei

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Target Projectile CN Attempt result
208Pb 137Cs 345Uts Reaction yet to be attempted
209Bi 136Xe 345Uts Reaction yet to be attempted
228Ra 115In 343Uts Reaction yet to be attempted
227Ac 116Cd 343Uts Reaction yet to be attempted
232Th 109Ag 341Uts Reaction yet to be attempted
231Pa 110Pd 341Uts Reaction yet to be attempted
238U 103Rh 341Uts Reaction yet to be attempted
237Np 104Ru 341Uts Reaction yet to be attempted
244Pu 99Tc 343Uts Reaction yet to be attempted
243Am 100Mo 343Uts Reaction yet to be attempted
250Cm 93Nb 343Uts Reaction yet to be attempted
249Bk 96Zr 345Uts Reaction yet to be attempted
252Cf 89Y 341Uts Reaction yet to be attempted
254Es 88Sr 342Uts Reaction yet to be attempted
257Fm 87Rb 344Uts Reaction yet to be attempted
258Md 86Kr 344Uts Reaction yet to be attempted
259No 81Br 340Uts Reaction yet to be attempted
262Lr 82Se 344Uts Reaction yet to be attempted
267Rf 75As 342Uts Reaction yet to be attempted
268Db 76Ge 344Uts Reaction yet to be attempted
271Sg 71Ga 342Uts Reaction yet to be attempted
274Bh 70Zn 344Uts Reaction yet to be attempted

Significance

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Untriseptium is sometimes called feynmanium (symbol Fy) because Richard Feynman noted[3] that a simplistic interpretation of the relativistic Dirac equation 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.[4]

Bohr model breakdown

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The Bohr model exhibits difficulty for atoms with atomic number greater than 137, for the speed of an electron in a 1s electron orbital, v, is given by

where Z is the atomic number, and α is the fine structure constant, a measure of the strength of electromagnetic interactions.[5] Under this approximation, any element with an atomic number of greater than 137 would require 1s electrons to be traveling faster than c, the speed of light. Hence the non-relativistic Bohr model is clearly inaccurate when applied to such an element.

The Dirac equation

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The relativistic Dirac equation also has problems for Z > 137, for the ground state energy is

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 Klein paradox.[6]

More accurate calculations including the effects of the finite size of the nucleus indicate that the binding energy first exceeds 2mc2 for Z > Zcr ≈ 173. For Z > Zcr, if the innermost orbital is not filled, the electric field of the nucleus will pull an electron out of the vacuum, resulting in the spontaneous emission of a positron.[7]

See also

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References

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  1. ^ Seaborg, G. T. (ca. 2006). "transuranium element (chemical element)". Encyclopædia Britannica. Retrieved 2010-03-16. {{cite web}}: Check date values in: |date= (help)
  2. ^ Cwiok, S.; Heenen, P.-H.; Nazarewicz, W. (2005). "Shape coexistence and triaxiality in the superheavy nuclei". Nature. 433 (7027): 705. Bibcode:2005Natur.433..705C. doi:10.1038/nature03336. PMID 15716943. {{cite journal}}: More than one of |pages= and |page= specified (help)
  3. ^ Elert, G. "Atomic Models". The Physics Hypertextbook. Retrieved 2009-10-09.
  4. ^ Walter Greiner and Stefan Schramm (2008). "Resource Letter QEDV-1: The QED vacuum". American Journal of Physics. 76 (6): 509. Bibcode:2008AmJPh..76..509G. doi:10.1119/1.2820395., and references therein.
  5. ^ Eisberg, R.; Resnick, R. (1985). Quantum Physics of Atoms, Molecules, Solids, Nuclei and Particles. Wiley.
  6. ^ Bjorken, J. D.; Drell, S. D. (1964). Relativistic Quantum Mechanics. McGraw-Hill.
  7. ^ Greiner, W.; Schramm, S. (2008). "American Journal of Physics". 76: 509. {{cite journal}}: Cite journal requires |journal= (help), and references therein.

Category:Chemical elements category:hypothetical chemical elements