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This article is about an undiscovered element. Once it is discovered, this article will be edited with more information.
Unbinilium
120Ubn
Ra

Ubn

Usq
ununenniumunbiniliumunbiunium
Appearance
unknown
General properties
Name, symbol, number unbinilium, Ubn, 120
Pronunciation /nbˈnɪliəm/
Element category Alkaline earth metals
Group, period, block 2, 9, s
Mass number ?
Electron configuration ?
Physical properties
See Wikipedia
Atomic properties
see Wikipedia
Most stable isotopes
Main article: Isotopes of unbinilium
iso NA half-life DM DE (MeV) DP
303Ubn syn ~0.01 s α unknown 299Og
299Ubn syn ~0.01 s α 295Og
vter

Unbinilium, Ubn, is the temporary name for element 120. Wikipedia has an article, Unbinilium, which addresses this element at length. This article focuses on topics Wikipedia does not: isotopes far from N = 184, which isotopes can actually form, and how long the element will be present.

There are a large number of neutron-rich Ubn isotopes which can form. All will disappear within 1000 sec after the event which led to their formation. There are also many isotopes near the N = 184 and N = 196 shell closures, but these cannot form, except by physicist-catalyzed reactions.

While this element can exist in nature as a nuclear phenomenon, its chemistry exists only in the laboratory.

Synthesis of Ubn has been reported, but not confirmed. It has been argued (see the Wikipedia article mentioned above) that Ubn may be the limit for current fusion-evaporation techniques.

Nuclear properties[]

Information sources[]

Wikipedia's article "Unbinilium" has a section addressing predicted nuclear properties, That section is limited to consideration of Ubn isotopes with neutron counts near 184. This article focuses on isotopes not reported on by Wikipedia, It uses two main resources chosen because of their independence from one another. A third source furnishes quantitative information over a more limited range.

At least one document maps half-life and decay mode for elements below Z = 175 from the neutron dripline down to isotopes which are too neutron-poor to survive any appreciable length of time[1]. Maps on pp 15 & 18 address the entire (Z,N) region covered, but report only the dominant decay mode and report half-lives only to within a band three orders of magnitude wide (0.001 - 1 sec, for example). More detailed estimates of these properties can be extracted from maps on pp 11 & 12, but only for a limited range of Z and N. Half-life data are reported by colors, which makes numerical estimates laborious to produce. This document is connected to Japan's KTUY model.

An independent map of half-lives and decay modes exists[2]. This one is limited to A = 339, as well as to Z = 132. It does not show short-lived isotopes well, and gives half-lives only within rather broad and awkward bands. It does show multiple decay modes for single nuclides, although this feature is hard to read. It originates from models used by the Russian agency JINR, so is completely independent of [1].

Japan Atomic Energy Agency (JAEA) maintains an on-line chart of nuclides which includes decay properties of many predicted nuclides[3] - unlike charts published by Korea Atomic Energy Research Institute (KAERI) or the (U.S.) National Nuclear Data Center (NNDC). This chart gives separate numerical values for partial half-lives against fission, beta emission (both b- and b+), and alpha emission. These appear to be systematically too long, but are probably reliable to within an order of magnitude.

Predicted properties[]

Even-N isotopes from the neutron dripline down to 385Ubn decay predominantly by beta emission with half-lives in the 0.001 - 1 sec range. Half-lives aren't reported, but the properties of beta decay indicate that half-lives close to 0.001 sec are likely[4]. Odd-N drops in this band decay by neutron emission.

All isotopes in the band 384Ubn to 368Ubn are predicted to have half-lives in the 0.001 - 1 sec range. Dominant decay modes are a mixture of fission and beta emission. Which mode dominates depends on N, with specific values of N associated with fission over a range of Z values. It is likely that both modes are significant for all isotopes.

Isotopes in the band 367Ubn to 339Ubn are predicted to decay by beta emission. With the exception of 342Ubn to 340Ubn, all have half-lives in the 0.001 - 1 sec range. The exceptions probably have half-lives in the 1 - 10 sec range.

338Ubn to 335Ubn are predicted to decay by fission and to have half-lives below 0.001 sec. Most are predicted to have very short half-lives..

[1] predicts a gap from 334Ubn to 317Ubn, which is predicted to be occupied by nuclear drops or very short-lived nuclides.

[2] reports isotopes with half-lives above 10-6 sec in the band 318Ubn - 315Ubn. Of these, 317Ubn has a half-life in the 1 sec - 1 day band; and all others have half-lives in the 0.001 - 1 sec band. They are all predicted to decay by fission. [1] shows no sign of this stable zone. [2] also shows 333Ubn as having a half-life in the 10-6 - 0.001 sec range, which extends the pattern shown in Fig. 1 of [2], but also requires a much longer half-life than that document indicates is possible.

[1] predicts 315Ubn to 310Ubn will decay by quickly and by fission. Except for the long half-life predicted at 315Ubn, [2] agrees.

[1] predicts that 309Ubn to 307Ubn will decay by alpha emission with half-lives in the 10-6 - 0.001 sec range. [2] indicates fission decay and shorter half-lives.

Both [1] and [2] agree that 306Ubn should decay by alpha emission with a sub-microsecond half-life.

[3] shows a dip in alpha-decay partial half-lives between 308Ubn and 306Ubn. Above 308Ubn, the longer partial half-lives are masked by onset of rapid decay by fission. This band is located just above the shell closure at N = 184, where it is expected.

Below 306Ubn, studies of decay properties become more numerous. It is beyond the scope of this article to compare them or assess what the actual properties of Ubn isotopes may be. One thing which can be noted is the prediction in [3] that 303Ubn and 299Ubn will have the longest half-lives in this region, at around 0.01 sec.

The lightest isotope reported by any of [1], [2] or [3] is 283Ubn. There may be a few lighter nuclides with half-lives in the 10-14 - 10-9 sec range, but half-lives will quickly decline below the minimum needed for a nuclear drop to qualify as a nuclide.

Occurrence[]

Formation[]

All even-N isotopes from the neutron dripline to 385Ubn can form, either directly as material is ejected from a disintegrating neutron star, as fission infall from larger nuclides, or by a chain of beta decays from directly-formed nuclides. All isotopes in the band 384Ubn to 335Ubn can form the same way, although direct formation is unlikely at lower N.

No isotopes lighter than 335Ubn are likely to form. Beta-decay chains with proper A values starting near the neutron dripline are terminated by fission at Z < 120. Note that termination requires rapid decay by fission. Nuclides whose half-lives are comparable with beta-emission half-lives do not terminate beta-decay chains.

It is improbable that neutron capture can form any Ubn isotope.

Persistence[]

335Ubn and heavier isotopes will vanish within 1000 sec after a supernova or neutron star merger which led to their formation, or lie at higher Z than beta-decay chains which end in nuclides which fission with a half-life not much greater than 1 sec.

334Ubn through 316Ubn lie at a higher Z than the terminating nuclides of short-lived beta-decay chains in this mass range.

315Ubn and lighter isotopes are predicted to have short half-lives and to be incapable of forming via beta decay from the dripline.

Atomic properties[]

Wikipedia's article "Unbinilium" addresses the element's atomic properties and chemistry in some detail. One point it does not make is that, while Ubn nuclei can form, they do not persist long enough to reach an environment cool enough to allow chemical processes. The chemistry of Ubn is entirely synthetic.

References[]

  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 "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. 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 “Systematic Study of Decay Properties of Heaviest Elements.”; Y. M. Palenzuelaa, L. F. Ruiza, A. Karpov, and W. Greiner; Bulletin of the Russian Academy of Sciences, Physics.  Vol . 76, No.11, pp 1165 – 1177; 2012
  3. 3.0 3.1 3.2 3.3 "Chart of the Nuclides, 2014", Japan Atomic Energy Agency; website available using "chart of nuclides" and "JAEA" as internet search terms.
  4. "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".
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

(10-2-20)

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