Untriseptium: Difference between revisions

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	{{Infobox untriseptium}}
	'''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.

			{{Redirect category shell\|1=
	The name ''untriseptium'' is a temporary ] ].
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		⚫	]
	== Significance ==
	Untriseptium is sometimes called '''feynmanium''' (symbol Fy) because ] noted<ref>
	{{cite web
	\|first=G.\|last= Elert
	\|date=
	\|title=Atomic Models
	\|url=http://physics.info/atomic-models/
	\|work=The Physics Hypertextbook
	\|accessdate=2009-10-09
	}}</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>

	=== Bohr model breakdown {{Anchor\|Bohr model}} ===
	The ] exhibits difficulty for atoms with atomic number greater than 137, for the speed of an electron in a ], ''v'', is given by

	:<math>v = Z \alpha c \approx \frac{Z c}{137.036}</math>

	where ''Z'' is the ], and ''α'' is the ], a measure of the strength of electromagnetic interactions.<ref>{{cite book
	\|first1=R. \|last1=Eisberg\|first2= R.\|last2= Resnick
	\|year=1985
	\|title=Quantum Physics of Atoms, Molecules, Solids, Nuclei and Particles
	\|publisher=]
	\|isbn=
	}}</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.

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

	:<math>E=m c^2 \sqrt{1-Z^2 \alpha^2}</math>

	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>
	{{cite book
	\|first1=J. D.\|last1= Bjorken\|first2=S. D.\|last2= Drell
	\|year=1964
	\|title=Relativistic Quantum Mechanics
	\|publisher=]
	\|isbn=
	}}</ref>

	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>
	{{cite journal
	\|first1=W. \|last1=Greiner\|first2= S. \|last2=Schramm
	\|year=2008
	\|title=]
	\|volume=76 \|pages=509
	\|doi=
	}}, and references therein.</ref>

	==See also==
	* ]
	* ] – ]
	* ]
	* ]

	== References ==
	{{Reflist}}

	{{Compact extended periodic table}}

	]
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Latest revision as of 04:14, 2 February 2023

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