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Seaborgium, Sg, is the name of element 106. Wikipedia has an article which provides a lot of information about the element.  This article will focus on things Wikipedia does not stress: heavy isotopes and formation.

Odd-N isotopes 277Sg and heavier, and even-N isotopes 284Sg and heavier can form. Maximum half-lives are reached in the lower 280s, and may be as great as 10 hrs. These isotopes may survive long enough to become part of supernova or kilonova (neutron star merger) remnants. They will disappear completely, though, within 2 - 3 months.

Lighter isotopes in the 278Sg to 272Sg band decay rapidly by fission.

A review of observed Sg isotopes reveals a charming detail. An isomer, 263mSg, has been synthesized via 249Cf(18O,4n)263mSg. Its ground state, 263Sg, has only been observed as a descendant of higher-Z elements. [Footnote: Wikipedia's "Isotopes of Seaborgium" article contains an error in its "Decay Products". 271Ds alpha decays via 267Hs to 263Sg; 267Ds decays to 259Sg. The table entry should read "271Ds, 267Hs".]

Nuclear properties[]

INFORMATION SOURCES[]

This article uses two main resources chosen because of their independence from one another. A third source provides quantitative data over a 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. It originates from models used by the Russian agency JINR, so is completely independent of Ref. 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 in most cases.

The U.S.'s Los Alamos National Laboratory (LANL) contains tabulated partial half-life data for alpha and beta decay(4). If it included fission, it would be a primary resource for this article, but it does not. Where fission is not an issue, though, it constitutes a third independent source of decay properties.

PREDICTED PROPERTIES[]

Isotopes from the neutron dripline down to 299Sg are predicted to decay primarily by beta emission, usually with half-lives in the 0.001 - 1 sec range. Isotopes at the light end of this band are likely to decay by a mixture of beta emission and fission.

Between 298Sg and 292Sg, fission is predicted to be the dominant mode for decay. Most half-lives will be in the 0.001 - 1 sec range, although a few has somewhat shorter half-lives. In all cases, beta decay is likely to be an important secondary decay mode. Half-lives are expected to be a few seconds at most.

Beta decay is predicted to predominate for all odd-N isotopes in the band 293Sg to 281Sg, There is some disagreement between sources over half-lives; but it appears that maximum half-lives are under 10 hrs. Even-N isotopes 288Sg and 286Sg are predicted to have a fission branch, but to be dominated by beta decay. The half-life of 286Sg may be up to 10 hr.

284Sg is predicted to decay principally by fission, but to have a significant beta-decay branch. It's half-life has been predicted to be on the order of 1000 sec.

282Sg is predicted to decay by fission with a half-life of a few minutes. It is not expected to have a significant beta-decay branch.

Decay by fission is expected to prevail in the band 280Sg to 272Sg and half-lives are predicted to be less than 1 sec. No beta-decay branch is expected for any of these isotopes.

270Sg and 268Sg are predicted to decay principally by fission with half-lives < 0.1 sec. Both have been predicted to have an alpha-decay branch, but no beta decay. N = 162 for 268Sg, which would give it a nonspherical (deformed) shape but a closed shell of neutrons. The known isotopes 271Sg and 269Sg are consistent with inhibited fission in odd-N isotopes.

Fission is observed in 267Sg and lighter isotopes. This odd phenomenon of fission setting in just below a shell closure is similar to what has been predicted to occur near 354Ubh.

The lightest isotope reported in the vicinity of N = 184 by any of Refs. 1 through 3 is 247Sg. There may be a few lighter nuclides with half-lives in the 10-14 - 10-09 sec range in this region, but half-lives will quickly decline below the minimum needed for a nuclear drop to qualify as a nuclide.

Ref. 1 predicts that 3 isotopes in the band 233Sg to 231Sg will have half-lives over 10-09 sec. 233Sg is predicted to decay by fission and have a half-life in the 10-06 - 0.001 sec range. The others are predicted to decay by alpha emission with half-lives under 0.001 sec.

OCCURRENCE[]

FORMATION[]

Sg isotopes from the neutron dripline to 285Sg can form. Fission-decaying nuclides with Z < 106 with near A = 295 can be expected to reduce the quantity of material which reaches Sg, but is not expected to completely block any decay chains.

It appears likely that odd-N isotopes between 283Sg and 277Sg can form. The even-N nuclide 284Rf might decay entirely by fission, but it seems more likely that a beta-decay branch for 284Rf exists, which implies that 284Sg is likely to form. It is likely that 282Rf, 280Rf, and 278Rf do not have a beta-decay branches, so that 282Sg, 280Sg, and 278Sg cannot form.

For 276Sg and lighter, even-N isotopes cannot form. Beta decay chains leading to them are interrupted by fission-decaying Rf isotopes. Decay chains leading to 275Sg and 273Sg terminate at Db. 271Sg does not occur either, but the decay chain leading to it is blocked by a series of steps where fission predominates, although some beta decay occurs.

270Sg and lighter isotopes are unlikely to form,

Since both high-A nuclides ejected from a disintegrating neutron star and large nuclides built up by rapid neutron capture can cover the entire band of Sg isotopes which can form, both neutron star mergers and supernovae contribute to the production of Sg.

PERSISTENCE[]

Half-lives of isotopes in the 293Sg to 281Sg may be as much as 10 hrs. In principle, some could persist for as much as three months after a supernova, neutron star merger, or other event which led to their formation. Other isotopes are expected to persist for shorter times. They are present in detectable amounts for a much shorter time,

ATOMIC PROPERTIES[]

Wikipedia's article "Seaborgium" addresses the element's atomic properties and chemistry in some detail. It is unlikely that any Sg can survive, outside the laboratory, to reach an environment cool enough for chemical interactions to occur.

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. “Systematic Study of Decay Properties of Heaviest Elements.”; Y. M. Palenzuela, 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. "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".

5. "Isotopes of Seaborgium", Wikipedia article.

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

(11-07-20)

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