Untriennium

Untriennium
Symbol	Ute
Number	139
Group, Period	N/A, 8
Mass number	-
Electronic properties
Electrons per shell	???
Discovery information
Discoverer	N/A
Date discovered	N/A
Location discovered	N/A

Untriennium, Ute, is the temporary name for element 139. Isotopes are predicted in the bands ⁴⁵²Ute to ³⁹⁶Ute, ³⁷²Ute to ³⁶⁶Ute, and ³⁶⁰Ute to ³⁵⁹Ute. There may be isotopes in the band from the neutron dripline to ⁴⁵³Ute, but it is not possible to predict which ones are possible. Reported half-lives are all less than 1 hr, and most are under 1 sec. Thirty six isotopes in the bands ⁴⁵²Ute to ⁴³⁷Ute and ⁴²³Ute to ⁴⁰³Ute are predicted to form. Two predicted isotopes, ⁴³⁹Ute and ⁴³⁷Ute, 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

INFORMATION SOURCES

While studies addressing specific issues have been carried out to very high N⁽¹⁾. and to moderate Z⁽²⁾, (Z,N) or (Z,A) maps predicting half-lives and decay modes are almost completely limited to the region below Z = 130 and N = 220. There appears to be only one such map which extends beyond that region and is accessible⁽³⁾.

(Z,N) maps for half-life and decay mode in Ref. 3 extend as high as Z = 175 and N = 333. Half-lives are reported as bands 3 orders of magnitude wide (0.001 - 1 sec, for example), and should be considered accurate only to within +/- orders of magnitude (presumably from band center. (A nuclide reported to be in the 0.001 - 1 sec band should be considered to have a possible half-life between 10^-4.5 sec and 10^1.5 sec.) Decay modes are limited alpha emission, beta emission, proton emission, and fission; and to the principal one for each nuclide. There are areas where two modes (or more) may be important, meaning that small uncertainties is model parameters could have produced different results. It is also possible that cluster decay may become important above the neutron shell closures at N = 228 and 308.

Ref. 3 does have two significant weakness in the way data are presented. Nuclides which are beta-stable are identified by black squares, overwriting decay mode and half-life information. In addition, nuclides having half-lives less than 10^-09 sec are not reported, which obscures the distinction between nuclides having half-lives in the 10^-09 and 10^-14 sec band and nuclear drops whose half-life is under 10^-14 sec.

Above Z around 126, predictions in Ref. 3 may not reach the neutron dripline. This can be an important limitation because the only processes which can form nuclei at more than atoms / star quantity generate very neutron-rich nuclei. It is possible to to make a crude, but conservative (high N) guess for the dripline's location by averaging predicted values for even-N nuclei.{See "The Final Element" (this wiki).} It is also possible to guess at regions of the (Z,N) or (Z,A) plane in which a fission barrier high enough to permit nuclides exists by using a first-order, liquid drop model. {See "Nuclear Guesswork" (this wiki).} Specific numbers are reported for these guesses, not with the expectation that they are accurate, but because they are consistent from element to element. They allow construction of a map which at least hints at where in the (Z,A) plane nuclides may be found.

GUESSED PROPERTIES

A simple liquid-drop picture indicates that ⁴⁹⁶Ute to ⁴⁵³Ute are unlikely to decay by neutron emission and are stable enough against fission to allow beta decay. Between ⁴⁷²Ute and ⁴⁵³Ute, Ref. 3 probably makes no predictions, but extrapolation from higher Z indicates that it would predict mainly short-lived, fission-decaying nuclides. Nuclear properties above ⁴⁵²Ute are highly uncertain, but it is possible that some relatively long-lived, beta-decaying isotopes of Ute are possible. It is possible to state that half-lives longer than 1 sec are implausible between the neutron dripline (nominally ⁴⁹⁶Ute) and ⁴⁵³Ute.

PREDICTED PROPERTIES

Isotopes in the band ⁴⁵²Ute - ⁴³⁹Ute are predicted to decay by beta emission. Predicted half-lives are in the 0.001 - 1 sec range. Actual half-lives are probably a few milliseconds and increase with declining N as the number of decays required to reach beta stability falls.

Isotopes in the band ⁴³⁸Ute - ⁴³⁰Ute are predicted to decay by fission, except for ⁴³⁷Ute. It appears to be possible for structure to destabilize a nuclide⁽⁴⁾, so the data reported appear to be realistic, At the upper end of this band, though, half-lives are unrealistically high, since partial half-lives against beta emission should be on the order of milliseconds this far from beta stability⁽⁵⁾. Half-lives decline as N falls, which is expected.

Isotopes in the band ⁴³⁰Ute - ⁴⁰⁴Ute are predicted to decay by beta emission. Half-lives are predicted to lie between 0.001 and 1 sec. Partial half-lives for beta decay should increase as N declines and the number of beta decays required to reach beta stability declines.

Between ⁴⁰³Ute and ³⁹⁹Ute, fission replaces beta emission as the dominant decay mode, with only beta emission dominant only in ⁴⁰²Ute. Odd-N isotopes are predicted to have 0.001 - 1 sec half-lives while even-N isotopes have shorter, and declining, half-lives.

³⁹⁸Ute is predicted to decay by fission with a half-life in the 10^-06 - 0.001 sec range. This is to be expected for an odd-N isotope.

³⁹⁷Ute and ³⁹⁶Ute have unexpectedly long half-lives and unexpected decay modes. It is likely that these are anomalies.

There is a gap from ³⁹⁵Ute to ³⁷³Ute in which properties are not reported. These may be short lived nuclides or nuclear drops whose half-life is less than 10^-14 sec. It appears to be the expected destabilized region above N = 228.

Between ³⁷²Ute and ³⁶⁶Ute drops are predicted to last long enough to be nuclides, but half-lives are predicted to be short. Fission is predicted to dominate throughout this band.

There is a gap from ³⁶⁵Ute to ³⁶¹Ute, within which half-lives are shorter than 10^-09 sec. Some drops in this band may be short-lived nuclides. ³⁶⁰Ute and ³⁵⁹Ute are predicted to be short-lived, with the former decaying via fission and the latter by alpha emission. Their properties are not unreasonable, but it is puzzling why they would appear so far from other nuclides which appear to be stabilized by the N = 228 closure.

N = 258 CLOSURE

The model used to predict decay properties of Ute isotopes has a relatively weak neutron shell closure at N = 258. Some neutron-dripline studies have indicated a strong closure at N = 258. If that closure is strong, one or more isotopes in the band ³⁹⁶Ute to ³⁸⁰Ute may even have half-lives exceeding 1000 sec. Interpolating between ⁴⁷²Uhq and ²⁹³Cn gives a reasonable value for maximum half-life of any nuclides stabilized by a strong N = 258 closure of 0.5 yr. 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

Where nuclear drops between the neutron dripline (nominally ⁴⁹⁶Ute) and ⁴⁵³Ute can be nuclides, they may form. Heavier isotopes may form directly from disintegrating neutron star material, and the remainder may form via beta decay chains from lower-Z nuclides. Since some of these chains may be terminated by short-lived, fission-decaying nuclides, it is not possible to say which isotopes of Ute in this range can form.

Nearly all nuclear drops in the bands ⁴⁵²Ute to ³⁹⁶Ute, ³⁷²Ute to ³⁶⁶Ute, and ³⁶⁰Ute to ³⁵⁹Ute are predicted to be nuclides. All are too far from the neutron dripline to form directly. It is possible to simulate the formation of nuclides via decay chains using data from Ref. 3 and assuming an initial distribution close to the neutron dripline. Details of the model are provided in "Nuclear Decay Chains at High A" in this wiki. Per that model, 36 predicted isotopes; ⁴⁵²Ute to ⁴³⁹Ute, ⁴³⁷Ute, and ⁴²³Ute to ⁴⁰³Ute; can form.

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

PERSISTENCE

⁴³⁹Ute and heavier isotopes, plus ⁴³⁷Ute, will vanish within 1000 sec after a neutron star merger which led to their formation.

⁴³⁸Ute and ⁴³⁶Ute are predicted to decay by fission and have half-lives in the 1 - 1000 sec range, but cannot form due to fission at Z < 139.

⁴³⁵Ute to ⁴¹⁸Ute are blocked from forming via beta decay from the dripline by fission at Z < 139.

⁴¹⁷Ute through ⁴⁰⁵Ute are predicted to be short-lived, beta-decaying species,

⁴⁰⁴Ute and ⁴⁰³Ute are at the end of beta-decay chains, but have half-lives under 1 sec. They will vanish within 10^2.5 sec.

⁴⁰⁰Ute and lighter isotopes will vanish within 1000 sec.

Calculations done under maximum half-life assumptions and with all nuclides initially populated still point to all isotopes of Ute 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, If so, and if peak half-lives in the region do approach 0.5 yr, it is possible that one or more isotopes in the band ³⁹⁶Ute to ³⁸⁰Ute may persist for up to 60 yrs. If so, unlike all nuclides with A > 396, small quantities of nuclides in that band may be injected into a stellar system other than the one in which neutron star merger occurred.

Atomic properties

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

If this effect is small, Ute will be an active (superactinide) metal of the 8th period. Its electron configuration has been predicted⁽⁶⁾ to be [Og] 5g¹³ 6f² 7d² 8s² 8p²_1/2. (Note the 6f-7d change.)

References

1. for example, "Nuclear Energy Density Functionals: What Do We Really Know?"; Aurel Bulgac, Michael McNeil Forbes, and Shi Jin; Researchgate publication 279633220 or arXiv: 1506.09195v1 [nucl-th] 30 Jun 2015.

2. for example "Fission Mechanism of Exotic Nuclei"; Research Group for Heavy Element Nuclear Science; http://asrc.jaea.go.jp/soshiki/gr/HENS-gr/np/research/pageFission_e.html.; 17 Sept 17.

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

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

5. "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".

6. "Extended Periodic Table", Wikipedia.

7. 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)