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Unseptquadium
174Usq
Ubn

Usq

?
unsepttriumunseptquadiumunseptpentium?
Appearance
unknown
General properties
Name, symbol, number unseptquadium, Usq, 174
Pronunciation /nsɛptˈkwɒdiəm/
Element category Alkaline earth metals
Group, period, block 2, 9, s?
Mass number ?
Electron configuration ?
Physical properties
unknown
Atomic properties
unknown
Most stable isotopes
Main article: Isotopes of unseptquadium
iso NA half-life DM DE (MeV) DP
483Usq syn 10-6-0.001 α unknown 429Usb
482Usq syn 10-6-0.001 α unknown 428Usb
481Usq syn 10-6-0.001 α unknown 427Usb
480Usq syn 10-6-0.001 α unknown 426Usb
vter

Unseptquadium, Usq, is the temporary name for element 174. Isotopes are predicted between 493Usq and 469Usq (excluding probable artifacts), none of which have half-lives exceeding 0.001 sec. None of these predicted isotopes can form. Isotopes in the band 584Usq to 566Usq are likely, most of which may form. All Usq isotopes will be gone in less than 1000 sec. after the event which led to their formation.

Compound nuclei of Usq have been synthesised by smashing lead atoms with uranium atoms. These are not stable enough to be true atoms.

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 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. 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 506Usq to 469Usq.

506Usq and 503Usq 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.

502Usq to 494Usq is a gap, which might mean half-lives below 10-9 sec or might mean the model is going ragged at its edges.

Isotopes in the bands 493Usq through 492Usq and 489Usq to 486Usq decay mainly by alpha emission and probably have half-lives in the 10-9 - 10-6 range. (It is necessary to estimate these from adjacent nuclides.) These are not unrealistic, particularly if N = 318 is also neutron-magic like N = 308, A second gap exists from 491Usq to 490Usq, This gap, too, may reflect short alpha-decay half-lives or a breakdown of the model.

485Usq and 484Usq are reported to decay by positron emission or electron capture with half-lives between 0.001 to 1 sec. These are almost certainly artifacts; alpha decay and short half-lives are just above N = 308.

The main band lies between 483Usq and 470Usq. Format used to display these is: isotope(s); half-life in seconds; dominant decay mode; comments.

483Usq - 480Usq; 10-6 - 0.001; alpha; some half-lives are estimated based on adjacent nuclides.

479Usq - 473Usq; 10-9 - 10-6; alpha; some half-lives are estimated based on adjacent nuclides.

472Usq; < 10-9; unknown, probably fission

471Usq; 10-9 - 10-6; alpha

470Usq; < 10-9; unknown, probably fission

469Usq; 10-9 - 10-6; fission.

Unlike elements adjacent to it, no light isotopes (A around 450) are reported.

Guessed properties[]

A nuclear drop containing 174 protons and more than 583 neutrons must decay by neutron emission with a half-life under 10-14 sec. A drop with 174 protons and fewer than 232 neutrons must decay by spontaneous fission with a half-life under 10-14 sec. Nuclear drops in the band from 757Usq to 406Usq 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 757Usq to 676Usq are likely to decay by neutron emission but are stable against fission. Nuclides in this band are unlikely. Drops in the band 675Usq to 633Usq 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 584Usq to 566Usq are unlikely to decay by neutron emission and are stable against fission. Nuclides in this band are likely. Drops in the bands 632Usq to 585Usq and 565Usq to 461Usq 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 460Usq to 406Usq 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.

Occurence[]

Formation[]

584Usq to 566Usq 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.). Heavier Usq isotopes may form directly. Isotopes 579Usq to 566Usq 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 506Usq to 469Usq 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 < 174.

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

Persistence[]

All Usq 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 Usq 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. Usq is also large enough that nuclear shape may have an effect on electron structure, which might cause different isotopes of Usq to have different electronic structures. (That means it is no longer an element in the chemical sense.) Predictions of atomic or chemical properties of Usq are risky.

If these effects are small, and if the assumptions made in "Period 9 Elements" are valid, Usq 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.

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

(06-07-20)

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