Untriseptium

Untriseptium
137Uts
- ↑ Uts ↓ ? Extended periodic table untrihexium ← untriseptium → untrioctium
Appearance
unknown
General properties
Name, symbol, number	untriseptium, Uts, 137
Pronunciation	/uːntraɪˈsɛptiəm/
Element category	superactinides
Group, period, block	N/A, 8, g
Mass number	[396] (predicted)
Electron configuration	[Uuo] 5g116f37d18s28p2 (predicted) 2, 8, 18, 32, 43, 21, 9, 4 (predicted)
Physical properties
unknown
Atomic properties
unknown
Most stable isotopes
Main article: Isotopes of untriseptium
iso NA half-life DM DE (MeV) DP 396Uts (predicted) syn 1-32 s β 394Uts (predicted) syn 1-32 s α 390Utp
v • t • e • r

Untriseptium (pron.: /uːntraɪˈsɛptiəm/), Uts, is the temporary name for element 137. Isotopes are predicted in the bands ⁴⁵⁰Uts to ³⁹³Uts, ³⁷²Uts to ³⁶³Uts, and ³⁵⁶Uts. There may be isotopes in the band from the neutron dripline to ⁴⁵¹Uts, 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. Forty-one isotopes in the bands ⁴⁵⁰Uts to ⁴³³Uts and ⁴²³Uts to ⁴⁰¹Uts are predicted to form. All Uts isotopes, predicted or guessed, will last less than 1000 sec after the event which led to their formation.

Nuclear properties

Information sources

While studies addressing specific issues have been carried out to very high N. and to moderate Z, (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.

(Z,N) maps for half-life and decay mode in extend as high as Z = 175 and N = 333. Half-lives are reported as bands3 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.

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^-9 sec are not reported, which obscures the distinction between nuclides having half-lives in the 10^-9 and 10^-14 sec band and nuclear drops whose half-life is under 10^-14 sec.

Above Z around 126, predictions in 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.) 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.) 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 ⁴⁸⁹Uts to ⁴⁵¹Uts are unlikely to decay by neutron emission and are stable enough against fission to allow beta decay. Between ⁴⁷⁰Uts and ⁴⁵¹Uts, probably makes no predictions, but extrapolation from higher Z indicates that it would predict mainly short-lived, fission-decaying nuclides. Nuclear properties above ⁴⁵⁰Uts are highly uncertain, but it is possible that some relatively long-lived, beta-decaying isotopes of Uts are possible. It is possible to state that half-lives longer than 1 sec are implausible between the neutron dripline (nominally ⁴⁸⁹Uts) and ⁴⁵¹Uts.

Predicted properties

Isotopes in the band ⁴⁵⁰Uts - ⁴³⁴Uts 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 ⁴³³Uts - ⁴²⁹Uts are predicted to decay by fission. It appears to be possible for structure to destabilize a nuclide, so the data reported appear to be realistic, Half-lives predicted are in the 0.001 - 1 sec range throughout the band. Beta emission is probably an important secondary decay mode.

Isotopes in the band ⁴²⁸Uts - ⁴⁰²Uts are predicted to decay by beta emission. Half-lives are predicted to lie between 0.001 and 1 sec. A fission decay branch probably exists for lighter isotopes in this band.

Between ⁴⁰¹Uts and ³⁹⁷Uts, fission becomes the dominant decay mode of even-N isotopes, whose half-lives decline rapidly to < 10^-09 sec. Odd-N isotopes beta-decay with half-lives in the 0.001-1 sec range.

Between ³⁹⁶Uts and ³⁹³Uts, predicted nuclear properties become difficult to understand. Half-lives and modes become somewhat random. Decay modes are predicted to be either beta emission or fission, with one exception. ³⁹⁴Uts is predicted to decay by alpha emission. That makes it unique among Uts isotopes, but also hints that it's decay mode may be an artifact. The only isotopes with half-lives predicted to exceed 1 sec are ³⁹⁴Uts and ³⁹⁶Uts (which is predicted to fission). Both are odd-odd nuclides, so can be expected to resist fission, but the abundance of short-lived odd-odd nuclides in their vicinity indicates that their half-lives do not greatly exceed 1 sec. Allowing 10^1.5 sec maximum half-life for those isotopes seems adequate. The remaining two isotopes are short-lived. ³⁹⁵Uts is predicted to decay by beta emission with a half-life in the 0.001 - 1 sec range and ³⁹³Uts is predicted to fission with a half-life in the 10^-6 - 0.001 sec range.

There is a gap from ³⁹²Uts to ³⁷³Uts 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.

Nuclides are predicted at ³⁷²Uts and from ³⁷⁰Uts to ³⁶³Uts. All are predicted to decay by fission. Half-lives increase as A declines, reaching the 0.001 - 1 sec range by ³⁶⁵Uts (for which N = 228), then falling abruptly.

³⁵⁶Uts is reported to decay by alpha emission with a 10^-6 - 0.001 sec half-life. It is not clear whether this is an artifact.

N = 258 CLOSURE

The model used to predict decay properties of Uts 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 ³⁹⁶Uts to ³⁸⁶Uts 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.

Occurence

Formation

Where nuclear drops between the neutron dripline (nominally ⁴⁸⁹Uts) and ⁴⁵¹Uts 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 at Z < 137 in short-lived, fission-decaying nuclides, it is not possible to say which isotopes of Uts in this range can form.

Nearly all nuclear drops in the bands ⁴⁵⁰Uts to ³⁹³Uts, ³⁷²Uts to ³⁶³Uts, and ³⁵⁶Uts 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 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, 41 predicted isotopes; ⁴⁵⁰Uts to ⁴³³Uts and ⁴²³Uts to ⁴⁰¹Uts; can form.

Neutron capture may be able to produce nuclides up to A around 360 before fission attrition stops further growth. It is implausible that neutron capture can form any Uts isotope. A small amount of fission infall may contribute to nuclides up to A = 406 (nominal).

Persistence

⁴³³Uts and heavier isotopes will vanish within 1000 sec after a neutron star merger which led to their formation. ⁴³³Uts itself ends a beta-decay chain, but fissions with a half-life under 1 sec.

⁴³²Uts to ⁴¹⁸Uts lie at higher Z than beta-decay chains which end in nuclides which decay by fission and have half-lives under 1 sec.

⁴¹⁷Uts through ⁴⁰¹Uts are predicted to be short-lived, beta-decaying species or to be unable to form because they lie at higher Z than beta-decay chains which end in nuclides which decay by fission with a half-life not much greater than 1 sec,

At ⁴⁰⁰Uts and below, all beta-decay chains end in short-lived, fissioning nuclides. No other isotopes of Uts persist for a significant time.

Calculations done under maximum half-life assumptions and with all nuclides initially populated still point to all isotopes of Uts 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 ³⁹⁶Uto to ³⁸⁶Uto may persist for up to 60 yrs. In addition, lighter isotopes in the band ³⁸⁵Uts to ³⁷⁶Uts may persist an equal lenght of time because they are daughers of long-lived precursors. Small quantities of several isotopes may be injected into a stellar system other than the one in which neutron star merger occurred.

Atomic properties

Electron structure of Uts has been predicted by several sources (see "Extended Periodic Table" in Wikipedia). Up to Z = 137, an atom's nucleus may be regarded as pointlike for the purpose of calculating electron configurations, which means predicted electron structure and behavior can be read more confidently. Its consensus electron configuration has been predicted to be [Og] 5g¹¹ 6f⁴ 8s² 8p²_1/2. (Note the 6f-7d change.)

Significance

Some (very few) call it "Feynmanium" because Feynman (supposedly) said it woud be the last possble element.

References

Other references are found in the wiki articles cited.

(07-02-20)

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