Untriseptium

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137 Uth ← untriseptium → Uto

↑
Uts
↓
Uos
General
Name, Symbol, Number untriseptium, Uts, 137
Chemical series Superactinides
Group, Period, Block g17, 8, g
Appearance unknown
Standard atomic weight [364] u (supposition)  g·mol−1
Electron configuration [Uuo] 5g18 8s1
Electrons per shell 2, 8, 18, 32, 50, 18, 8, 1
Physical properties
Phase presumably solid
Miscellaneous
Selected isotopes
Main article: Isotopes of untriseptium
iso NA half-life DM DE (MeV) DP
References

Untriseptium (pronounced /ˌʌntraɪˈsɛptiəm/) is a chemical element which has not yet been observed to occur naturally or be synthesised. Its atomic number is 137 and symbol is Uts.

The name untriseptium is a temporary IUPAC systematic element name.

Contents

[edit] History

The name untriseptium is used as a placeholder, as in scientific articles about the search for element 137. Transuranic elements (those beyond uranium) are, except for microscopic quantities and except for plutonium, always artificially produced, and usually end up being named for a scientist or the location of a laboratory that does work in atomic physics (see systematic element name for more information).

[edit] Significance

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:

v = Z \alpha c \approx \frac{Z c}{137.036}

where Z is the atomic number, and α is the fine structure constant, a measure of the strength of electromagnetic interactions.[1] 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 relativistic Dirac equation also has problems for Z>137, for the ground state energy is

E=m c^2 \sqrt{1-Z^2 \alpha^2}

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.[2]

More accurate calculations including the effects of the finite size of the nucleus indicate that the binding energy first exceeds 2 m c2 for Z>Zcr\approx173. 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.[3]



[edit] References

  1. ^ See for example R. Eisberg and R. Resnick, Quantum Physics of Atoms, Molecules, Solids, Nuclei and Particles, Wiley (New York: 1985).
  2. ^ James D. Bjorken and Sidney D. Drell, Relativistic Quantum Mechanics, McGraw-Hill (New York:1964).
  3. ^ Walter Greiner and Stefan Schramm, Am. J. Phys. 76, 509 (2008), and references therein.

[edit] External links

[edit] See also