Unpentseptium

Unpentseptium, Ups, is the temporary name for element 157. Isotopes are predicted between ⁴⁸⁵Ups and ⁴²⁸Ups. Reported half-lives are all less than 1 hr, and most are under 1 sec. Five isotopes in the band ⁴⁵⁶Ups to ⁴⁴⁹Ups can form. Beyond the region for which predictions are available, isotopes in the band ⁵⁶⁵Ups to ⁵⁴⁷Ups are likely. It is possible that all of them can form. ⁴⁵⁶Ups is expected to last for between 1 and 2 days. All other Ups 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. 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.

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" 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". 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

predicts isotopes ranging from ⁴⁸⁵Ups to ⁴²⁸Ups. Format used to display isotope properties is: isotope(s); half-life in seconds; dominant decay mode; comments.

⁴⁸⁵Ups - ⁴⁸³Ups; 10^-9 - 10^-6; fission.

⁴⁸²Ups - ⁴⁸⁰Ups; 10^-6 - 0.001; fission.

⁴⁷⁹Ups; 10^-9 - 10^-6; fission.  The short half-life of this isotope of Ups may reflect an even-N/odd-N effect.

⁴⁷⁸Ups; 0.001 - 1; fission.  There is a jump in half-life of at least 3 orders of magnitude between ⁴⁷⁹Ups and ⁴⁷⁸Ups.  Results in the band from ⁴⁷⁸Ups to ⁴⁷⁵Ups are not unrealistic if there is a shell closure at N = 318, but can't be called reliable.

⁴⁷⁷Ups; 1 - 1000; fission.  This half-life seems long since its half-life against beta decay should be short.  (also see ⁴⁷⁸Ups above)

⁴⁷⁶Ups - ⁴⁷⁵Ups; 0.001 - 1; fission.  (also see ⁴⁷⁸Ups above)

⁴⁷⁴Ups - ⁴⁶⁶Ups; 1 - 1000; alpha.  Both half-life and decay mode for these isotopes of Ups are not unrealistic if there are shell closures at both N = 308 and N = 318 and if half-lives are close to 1 sec.  Shell closures do not appear to enhance beta-decay half-lives. All nuclides in this band are at least four steps away from beta-stability, so beta decay is probably an important, although not dominant, mode.

⁴⁶⁵Ups - ⁴⁵⁹Ups; 0.001 - 1; beta.

⁴⁵⁸Ups; 1 - 1000; alpha. Beta decay in smaller nuclides does not show significant differences in half-life between odd-N and even-N nuclides. The half-life predicted is realistic if it does not greatly exceed 1 sec. 

⁴⁵⁷Ups 0.001 - 1; beta.

⁴⁵⁶Ups; 1 - 1000; alpha. As above, this is realistic if half-life is close to 1 sec.

⁴⁵⁵Ups; 0.001 - 1; beta.

⁴⁵⁴Ups; 1 - 1000; alpha. As above, this is realistic if half-life is close to 1 sec.

⁴⁵³Ups; 0.001 - 1; beta.

⁴⁵²Ups; 1 - 1000; alpha. As above, this is realistic if half-life is close to 1 sec.

⁴⁵¹Ups - ⁴⁴⁰Ups; 0.001 - 1; alpha.

⁴³⁹Ups - ⁴³³Ups; 10^-6 - 0.001; alpha, although fission may be a significant decay branch.

⁴³²Ups; 10^-6 - 0.001; fission.

⁴³¹Ups; 10^-9 - 10^-6; fission.

⁴³⁰Ups; 10^-6 - 0.001; fission.

⁴²⁹Ups - ⁴²⁸Ups; 10^-9 - 10^-6; fission.

Below N = 308, this pattern is to be expected, given a neutron shell closure at N = 308. Above this point, predictions become more confusing.

Guessed properties

Drops in the band ⁵⁶⁵Ups to ⁵⁴⁷Ups are unlikely to decay by neutron emission and are stable against fission. Nuclides in this band are likely. Drops in the band ⁵⁴⁶Ups to ⁴⁹¹Ups are unlikely to decay by neutron emission and require a moderate amount of structural correction energy. Nuclides in this band are unlikely. Below ⁴⁹¹Ups, predictions are available.

Occurence

Formation

⁵⁶⁵Ups to ⁵⁴⁷Ups 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".). These can form directly as neutron star material breaks up or by beta-decay chains from lower-Z nuclides. They are outside the range in which half-life predictions exist. They are all very neutron-rich, which implies half-lives under 1 sec are likely.

All nuclear drops in the band ⁴⁸⁵Ups to ⁴²⁸Ups 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 ⁴⁵⁷Ups or heavier isotopes are terminated at Z < 157 by nuclides which fission so quickly that no beta-decay branch is possible.

In order to determine whether ⁴⁵⁶Ups 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, ⁴⁵⁶Ups, ⁴⁵⁵Ups, ⁴⁵³Ups, ⁴⁵¹Ups, and ⁴⁴⁹Ups can form.

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

Persistence

⁴⁵⁷Ups and heavier isotopes will decay to the vanishing point within 1000 sec after a neutron star merger which led to their formation.

⁴⁵⁶Ups is predicted to have a half-life in the 1 - 1000 sec range, and to be fed by a chain of beta-decaying nuclides with half-lives predicted to be under 1 sec. It will persist for up to 10⁵ sec under maximum half-life assumptions. It is part of a beta-alpha-fission decay chain that persists for a maximum computed time under 125000 sec, so its own time-to-extinction wasn't tracked closely in the calculations.

⁴⁵⁵Ups, ⁴⁵³Ups, and ⁴⁵¹Ups are each part of a long-lived decay chain, but will vanish quickly themselves.

⁴⁴⁹Ups has a precursor predicted to have a half-life in the 1 - 1000 sec range. As above, it's worst case time-to-vanish will be on the order of 10⁵ sec.

No other isotopes of Ups persist for a significant time.

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

Atomic properties

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

If this effect is small, Ups will be a f-block metal of the 8th period (possibly d block). As such, it would also be classed as a superactinide. Its electron configuration has been predicted to be [Og] 5g¹⁸ 6f¹⁴ 7d³ 8s² 8p²_1/2.

References

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

(06-18-20)