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Unseptpentium
175Usp
?

Usp

?
unseptquadium? ← unseptpentiumunsepthexium
Appearance
unknown
General properties
Name, symbol, number unseptpentium, Usp, 175
Pronunciation /nsɛptˈpɛntiəm/
Element category unknown
Group, period, block N/A, 9?, unknown
Mass number [486] (predicted)
Physical properties
unknown
Atomic properties
unknown
Most stable isotopes
Main article: Isotopes of unseptpentium
iso NA half-life DM DE (MeV) DP
487Usp syn 1-1000+ sec fission
486Usp syn 1-1000+ sec fission
485Usp syn 1-1000+ sec fission
vter

Unseptpentium, Usp, is the temporary name for element 175. Isotopes are predicted between 494Usp and 471Usp (excluding probable artifacts), none of which have half-lives exceeding 10-6 sec (excluding probable artifacts). None of these predicted isotopes can form. Isotopes in the band 585Usp to 567Usp are likely, most of which may form. All Usp isotopes will be gone less than 1000 sec. after the event which led to their formation.

NUCLEAR PROPERTIES[]

Between Z = 175 and Z near 130, one set of predictions for half-life and principal decay mode has been published(1). Ref. 1 is publicly available and can be found via a search by paper title. Anyone interested in this element should study pp 15 and 18, which allow a given element to be understood in the context of adjacent nuclides.

These data are limited to nuclides for which N <= 333. Half-lives are presented in bands covering 3 orders of magnitude (0.001 sec to 1 sec, for instance) and are accurate to within +/- 3 orders of magnitude, which seems rather crude until the enormous extrapolation from what is known is taken into account, Minimum half-life is set at 10-9 sec, rather than 10-14 sec; which introduces a little uncertainty, but not a great deal because fission half-lives tend to transition quickly from values well above 10-9 sec to values well below 10-14 sec; and, while alpha-decay half-lives change more slowly, alpha emission is rarely dominant except where fission is suppressed. Significantly, beta-decay half-lives do not decline far below 10-3 sec, even for highly energetic decays, so there is little uncertainty about neutron-rich nuclides.

Ref. 1 does have one significant weakness. Nuclides which are beta-stable are identified by black squares, overwriting decay mode and half-life information. In many cases, these data can be estimated from adjacent nuclides.

No predictions exist for N > 333. The approach used for Z = 176 and above can be used at lower Z.

A boundary in the (Z,A) plane is constructed in "The Final Element" (this wiki) defining a region of that plane outside of which no nuclei exist. It does not predict where nuclei can exist within that region; but the first-order, liquid-drop model used to create that boundary can be used to guess at where nuclides may exist. Criteria used to guide these guesses are described in "Nuclear Guesswork" (this wiki). The resulting A(Z) ranges developed should not be considered accurate, but they are consistent from element to element.

PREDICTED PROPERTIES[]

Ref. 1 predicts isotopes ranging from 507Usp to 454Usp.

507Usp and 504Usp appear to be artifacts. N = 318 has been predicted(2) to be a neutron closure, but N = 229 or 232 is far above that closure.

503Usp to 495Usp is a gap, which might mean half-lives below 10-9 sec or might mean the model is going ragged at its edges.

The main band lies between 494Usp and 471Usp. Format used to display these is: isotope(s); half-life in seconds; dominant decay mode; comments.

494Usp - 488Usp; 10-9 - 10-6; alpha; these are not unrealistic, particularly if N = 318 is also neutron-magic like N = 308,

487Usp - 485Usp; 1 - 1000+; fission; these are almost certainly artifacts; alpha decay and short half-lives are expected for N slightly above 308.

484Usp4 - 472Usp; 10-9 - 10-6; alpha.

471Usp; 10-9 - 10-6; fission.

There is another gap from 470Usp to 458Usp. These drops are too proton rich to survive.

457Usp to 455Usp have half-lives between 10-9 to 10-6 sec and decay predominantly by alpha emission, but 454Usp is reported to have a millisecond-scale half-life. It would take a lot of structural correction to hold nuclear drops together long enough to make a nucleus. A few nanoseconds, maybe, but there are no reports of shell closures in this area strong enough to produce a msec half-lived nuclide.

GUESSED PROPERTIES[]

A nuclear drop containing 175 protons and more than 587 neutrons must decay by neutron emission with a half-life under 10-14 sec. A drop with 175 protons and fewer than 236 neutrons must decay by spontaneous fission with a half-life under 10-14 sec. Nuclear drops in the band from 762Usp to 411Usp are not required to decay either by neutron emission or by fission, so it is possible they will survive the 10-14 sec needed for them to become nuclides.

Nuclear drops in the band 762Usp to 677Usp are likely to decay by neutron emission but are stable against fission. Nuclides in this band are unlikely. Drops in the band 676Usp to 637Usp are likely to decay by neutron emission and require a moderate amount of structural correction energy. Nuclides in this band are improbable.

Drops in the band 585Usp to 567Usp are unlikely to decay by neutron emission and are stable against fission. Nuclides in this band are likely. Drops in the bands 636Usp to 586Usp and 566Usp to 467Usp are unlikely to decay by neutron emission and require a moderate amount of structural correction energy. Nuclides in these bands are unlikely. Drops in the band 466Usp to 411Usp are unlikely to decay by neutron emission but require large structural correction. Nuclides in this band are improbable.

COMPARISON[]

The two techniques described above were more or less consistent. Ref. 1 does predict far more nuclides than were estimated to be "likely". The technique for estimating where nuclides are likely to exist is conservative.

OCCURRENCE[]

FORMATION[]

585Usp to 567Usp are likely to be nuclides. Depending on the neutron dripline's actual location, nuclei in this A range may form when material over 700 - 800 meters deep is ejected from a neutron star during a merger. (See "Neutron Star", this Wiki.). Heavier Usp isotopes may form directly. Isotopes 579Usp to 567Usp are likely to form via beta decay chains from lower Z nuclides, although attrition due to fission or beta+neutron(s) decay can be expected.

Many nuclear drops in the band 507Usp to 454Usp are predicted to be nuclides. They are all too far from the neutron dripline to form directly, and cannot form from lower Z nuclides because beta decay chains terminate at Z < 175.

It is implausible that neutron capture can form any Usp isotope.

PERSISTENCE[]

All Usp isotopes are expected to decay away to nothing within 1000 sec after the neutron star merger which led to their formation.

ATOMIC PROPERTIES[]

Electron structure of Usp has not been studied closely, but it is likely to differ significantly from what's found at lower atomic numbers. It is likely that orbital theory breaks down between Z = 170 and Z = 175. While only the innermost electrons would be qualitatively different, other orbitals are likely to be affected sufficiently to change the ground state occupation. Usp is also large enough that nuclear shape may have an effect on electron structure, which might cause different isotopes of Usp to have different electronic structures. (That means it is no longer an element in the chemical sense.) Predictions of atomic or chemical properties of Usp are risky.

If these effects are small, and if the assumptions made in "Period 9 Elements" (this wiki) are valid, Usp will be a 9th period active metal.

REFERENCES[]

1. "Decay Modes and a Limit of Existence of Nuclei"; H. Koura; 4th Int. Conf. on the Chemistry and Physics of Transactinide Elements; Sept. 2011.

2.  “The Highest Limiting Z in the Extended Periodic Table”; Y.K. Gambhir, A. Bhagwat, and M. Gupta; Journal of Physics G: Nuclear and Particle Physics. 42 (12): 125105. DOI:10.1088/0954 3899/42/12/ 125105.

3. Other references are found in the wiki articles cited.Template:E176+

(06-7-20)

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