Unquadpentium

Unquadpentium, Uqp, is the temporary name for element 145. Isotopes are predicted between ⁴⁷³Uqp and ⁴¹⁰Uqp, and between ³⁷⁴Uqp and ³⁶⁷Uqp. Reported half-lives are all less than 1 hr, and most are under 1 sec. Twenty two isotopes in the bands ⁴⁵⁶Uqp to ⁴⁴⁵Uqp and ⁴²³Uqp to ⁴¹³Uqp can form. Beyond the region for which predictions are available, isotopes in the band ⁵¹⁹Uqp to ⁵¹⁸Uqp are likely. It is possible that all of them can form. Six predicted isotopes may persist for up to 2 days after the event which led to their formation. All other isotopes will last less than 1000 sec.

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 liquid-drop sketch developed in "The Final Element" (this wiki) for Z = 176 and above can be used to guess at where nuclides with Z < 175 and N > 333 may exist. Probability criteria for this purpose were set in "Nuclear Guesswork" (this wiki). Below Z = 171, it is necessary to look only at nuclear drops which are not expected to decay by neutron emission and require only normal amounts of structural correction energy in order to suppress spontaneous fission.

Predicted properties

Ref. 1 predicts isotopes ranging from ⁴⁷³Uqp to ⁴¹⁰Uqp, plus isotopes ranging from ³⁷⁴Uqp to ³⁶⁷Uqp. The gap between these bands may be short lived nuclides or nuclear drops whose half-life is less than 10^-14 sec. Format used to display isotope properties is: isotope(s); half-life in seconds; dominant decay mode; comments.

⁴⁷³Uqp - ⁴⁶²Uqp; <10^-6; fission. Two isotopes, ⁴⁷¹Uqp and ⁴⁶³Uqp are reported to have half-lives in the 10^-6 - 0.001 sec range, but such long-lived, isolated, fissioning nuclides appear to be artifacts.

⁴⁶¹Uqp - ⁴⁴⁶Uqp; 0.001 - 1; beta.

⁴⁴⁵Uqp - ⁴⁴⁴Uqp; 1 - 1000; fission. These nuclides are around 10 steps from beta stability, which means even a 1 sec partial half-life against beta decay is questionably long⁽²⁾, particularly in light of the shorter half-lives predicted for lighter, beta-decaying Uqp isotopes. They may be artifacts.

⁴⁴³Uqp - ⁴⁴⁰Uqp; 0.001 - 1; beta.

⁴³⁹Uqp - ⁴³⁶Uqp; 0.001 - 1000; fission. Ref 1 predicts a band of fission-decaying nuclides with N between 285 and 295. It appears to be possible for structure to destabilize a nuclide⁽³⁾, so short partial half-lives against fission in this region are plausible. Beta emission can be expected to be an important secondary decay mode.

⁴³⁵Uqp - ⁴²⁷Uqp; 0.001 - 1; beta.

⁴²⁶Uqp - ⁴¹⁷Uqp; 0.001 - 1000; mixed. Even-N isotopes in this band are predicted to decay by alpha emission with half-lives over 1 sec, odd-N isotopes are predicted to decay by beta emission with half-lives under 1 sec. This is not unrealistic if all half-lives are close to 1 sec.

⁴¹⁶Uqp - ⁴¹⁴Uqp; 0.001 - 1; mixed. Odd-Z, odd-N nuclides tend to have long fission half-lives, so the predicted beta decay of ⁴¹⁵Uqp and fission decay of the others is plausible.

⁴¹³Uqp; 10^-6 - 0.001; fission.

⁴¹²Uqp; 10^-9 - 10^-6; fission.

⁴¹¹Uqp; 0.001 - 1; fission. Half-life of this isotope is unexpectedly long.

⁴¹⁰Uqp; 10^-9 - 10^-6; fission.

This pattern is generally to be expected, given a neutron shell closure at N = 308. Presence of a fission-decaying band in the N = 285 - 295 range indicates requires nuclear structure.

Near the predicted N = 228 shell closure, properties of Uqp isotopes are reported to be

³⁷⁴Uqp - ³⁷³Uqp; 10^-9 - 10^-6; fission.

³⁷²Uqp - ³⁶⁹Uqp; <10^-9; fission.

³⁶⁸Uqp - ³⁶⁷Uqp; 10^-9 - 10^-6; alpha.

This is the pattern to be expected near a shell closure.

Guessed properties

Drops in the band ⁵¹⁹Uqp to ⁵¹⁸Uqp are unlikely to decay by neutron emission and are stable against fission. Nuclides in this band are likely. Drops in the band ⁵¹⁷Uqp to ⁴⁷⁹Uqp are unlikely to decay by neutron emission and require a moderate amount of structural correction energy. Nuclides in this band are unlikely. Below ⁴⁷⁹Uqp, predictions are available.

N = 258 CLOSURE

The model used to predict decay properties of Uqp isotopes has a relatively weak neutron shell closure at N = 258. Some neutron-dripline studies have indicated a strong closure at N = 258. Even a strong closure is unlikely to significantly enhance the stability of any isotopes of Uqp, although one or more isotopes in the band ³⁹⁶Uqp to ³⁹⁴Uqp may have half-lives exceeding 1000 sec. Half-lives significantly longer are unlikely. Either alpha decay or beta decay may occur in this band, but fission can be expected to be suppressed.

These are not predictions of decay properties for nuclides in the vicinity of N = 258. This entire exercise is qualitative guesswork. No numbers, but a tantalizing hint of what might be.

Occurrence

Formation

⁵¹⁹Uqp to ⁵¹⁸Uqp 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.). These can form directly as neutron star material breaks up or by beta-decay chains from lower-Z nuclides. The isotopes ⁵¹⁹Uqp to ⁵¹⁸Uqp are outside the range in which half-life predictions exist. They are all very neutron-rich, which implies half-lives under 1 sec^(1),(2) are likely.

Nearly all nuclear drops in the band ⁴⁷³Uqp to ⁴¹⁰Uqp, ³⁷⁴Uqp & ³⁷³Uqp, and ³⁶⁸Uqp & ³⁶⁷Uqp are predicted to be nuclides. They are all too far from the neutron dripline to form directly. All beta-decay chains which would lead to ⁴⁵⁷Uqp or heavier isotopes are terminated at Z < 145 by nuclides which fission so quickly that no beta-decay branch is possible.

In order to determine whether ⁴⁵⁶Uqp and lighter isotopes can form, it is necessary to model the evolution of initial material by radioactive decay. Details of the model are provided in "Nuclear Decay Chains at High A" in this wiki. Per that model, 22 isotopes; ⁴⁵⁶Uqp to ⁴⁴⁵Uqp, ⁴²³Uqp to ⁴¹⁵Uqp, and ⁴¹³Uqp; can form. Isotopes below ⁴⁴⁶Uqp result from using a model which populated all nuclides at time zero.

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

Persistence

Isotopes ⁴⁴⁶Uqp and heavier isotopes will decay to nothing within 1000 sec after a neutron star merger which led to their formation.

⁴⁴⁵Uqp and ⁴⁴⁴Uqp are predicted to decay by fission, have half-lives in the 1 - 1000 sec range, and occur at the end of beta-decay chains. They may persist for up to 105000 sec.

⁴⁴³Uqp to ⁴¹⁸Uqp are blocked from forming via beta decay from the dripline by fission at Z < 145.

⁴¹⁷Uqp to ⁴¹⁵Uqp are predicted to be short-lived, beta-decaying nuclides.

⁴¹³Uqp is predicted to have a half-life under 1 sec, decay by fission, and be at the end of a decay chain. It can be expected to disappear within 10^2.5 sec.

No other isotopes of Uqp persist for a significant time.

Calculations done under maximum half-life assumptions and with all nuclides initially populated still point to all isotopes of Uqp vanishing within 10^5.5 (3.16E05) sec.

N = 258 SHELL CLOSURE

Some studies of the neutron dripline indicate a strong shell closure at N = 258, instead of the relatively weak one occurring in the predictive models, It is unlikely that this closure will produce any significantly long-lived Uqp isotopes.

Atomic properties

Electron structure of Uqp has been predicted by several sources (see "Extended Periodic Table" in Wikipedia). However, these predictions should be used with caution. Uqp is large enough that nuclear shape may have an effect on electron structure, which might cause different isotopes of Uqp to have different electronic structures. (That means it is no longer an element in the chemical sense.)

If this effect is small, Uqp will be an active (superactinide) metal of the 8th period. Its electron configuration has been predicted⁽⁴⁾ to be [Og] 5g¹⁸ 6f³ 7d² 8s² 8p²_1/2.

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. "Nuclear Properties for Astrophysical Applications"; P. Moller & J. R. Nix; Los Alamos National Laboratory website; search by "LANL, T2", then "Nuclear Properties for Astrophysical Applications".

3. "Magic Numbers of Ultraheavy Nuclei"; Vitali Denisov; Physics of Atomic Nuclei; researchgate.net/publications/225734594; July 2005.

4. "Extended Periodic Table", Wikipedia.

5. Other references are found in the wiki articles cited.

9-Period Periodic Table of Elements
1	1 H																																																																	2 He
2	3 Li	4 Be																																																																	5 B	6 C	7 N	8 O	9 F	10 Ne
3	11 Na	12 Mg																																																																	13 Al	14 Si	15 P	16 S	17 Cl	18 Ar
4	19 K	20 Ca																																																																	21 Sc	22 Ti	23 V	24 Cr	25 Mn	26 Fe	27 Co	28 Ni	29 Cu	30 Zn	31 Ga	32 Ge	33 As	34 Se	35 Br	36 Kr
5	37 Rb	38 Sr																																																																	39 Y	40 Zr	41 Nb	42 Mo	43 Tc	44 Ru	45 Rh	46 Pd	47 Ag	48 Cd	49 In	50 Sn	51 Sb	52 Te	53 I	54 Xe
6	55 Cs	56 Ba																																																					57 La	58 Ce	59 Pr	60 Nd	61 Pm	62 Sm	63 Eu	64 Gd	65 Tb	66 Dy	67 Ho	68 Er	69 Tm	70 Yb	71 Lu	72 Hf	73 Ta	74 W	75 Re	76 Os	77 Ir	78 Pt	79 Au	80 Hg	81 Tl	82 Pb	83 Bi	84 Po	85 At	86 Rn
7	87 Fr	88 Ra																																																					89 Ac	90 Th	91 Pa	92 U	93 Np	94 Pu	95 Am	96 Cm	97 Bk	98 Cf	99 Es	100 Fm	101 Md	102 No	103 Lr	104 Rf	105 Db	106 Sg	107 Bh	108 Hs	109 Mt	110 Ds	111 Rg	112 Cn	113 Nh	114 Fl	115 Mc	116 Lv	117 Ts	118 Og
8	119 Uue	120 Ubn																															121 Ubu	122 Ubb	123 Ubt	124 Ubq	125 Ubp	126 Ubh	127 Ubs	128 Ubo	129 Ube	130 Utn	131 Utu	132 Utb	133 Utt	134 Utq	135 Utp	136 Uth	137 Uts	138 Uto	139 Ute	140 Uqn	141 Uqu	142 Uqb	143 Uqt	144 Uqq	145 Uqp	146 Uqh	147 Uqs	148 Uqo	149 Uqe	150 Upn	151 Upu	152 Upb	153 Upt	154 Upq	155 Upp	156 Uph	157 Ups	158 Upo	159 Upe	160 Uhn	161 Uhu	162 Uhb	163 Uht	164 Uhq	165 Uhp	166 Uhh	167 Uhs	168 Uho	169 Uhe	170 Usn	171 Usu	172 Usb
9	173 Ust	174 Usq
Alkali metal Alkaline earth metal Lanthanide Actinide Superactinide Transition metal Post-transition metal Metalloid Other nonmetal Halogen Noble gas predicted predicted predicted predicted predicted predicted predicted predicted predicted

(06-29-20)