List of elements by stability of isotopes

Atomic nuclei consist of protons and neutrons, which attract each other through the nuclear force, while protons repel each other via the electric force due to their positive charge. These two forces compete, leading to some combinations of neutrons and protons being more stable than others. Neutrons stabilize the nucleus, because they attract protons, which helps offset the electrical repulsion between protons. As a result, as the number of protons increases, an increasing ratio of neutrons to protons is needed to form a stable nucleus; if too many or too few neutrons are present with regard to the optimum ratio, the nucleus becomes unstable and subject to certain types of nuclear decay. Unstable isotopes decay through various radioactive decay pathways, most commonly alpha decay, beta decay, or electron capture. Many other rare types of decay, such as spontaneous fission or cluster decay are known. (See radioactive decay for details.)

This is a list of the chemical elements and their isotopes, listed in terms of stability.

Of the first 82 elements in the periodic table, 80 have isotopes considered to be stable.[1] The 83rd element, bismuth, was traditionally regarded as having the heaviest stable isotope, bismuth-209, but in 2003 researchers in Orsay, France, measured the half-life of 209
Bi
to be 1.9×1019 years.[2][3] Technetium, promethium (atomic numbers 43 and 61, respectively[a]) and all the elements with an atomic number over 82 only have isotopes that are known to decompose through radioactive decay. No undiscovered elements are expected to be stable; therefore, lead is considered the heaviest stable element. However, it is possible that some isotopes that are now considered stable will be revealed to decay with extremely long half-lives (as with 209
Bi
). This list depicts what is agreed upon by the consensus of the scientific community as of 2016.[1]

For each of the 80 stable elements, the number of the stable isotopes is given. Only 90 isotopes are expected to be perfectly stable, and an additional 163 are energetically unstable, but have never been observed to decay. Thus, 253 isotopes (nuclides) are stable by definition (including tantalum-180m, for which no decay has yet been observed). Those that may in the future be found to be radioactive are expected to have half-lives longer than 1022 years (for example, xenon-134).

Of the chemical elements, only one element (tin) has 10 such stable isotopes, one (xenon) has eight isotopes, four have seven isotopes, eight have six isotopes, ten have five isotopes, nine have four isotopes, five have three stable isotopes, 16 have two stable isotopes, and 26 have a single stable isotope.[1]

Additionally, about 29 nuclides of the naturally occurring elements have unstable isotopes with a half-life larger than the age of the Solar System (~109 years or more).[b] An additional four nuclides have half-lives longer than 100 million years, which is far less than the age of the solar system, but long enough for some of them to have survived. These 33 radioactive naturally occurring nuclides comprise the radioactive primordial nuclides. The total number of primordial nuclides is then 253 (the stable nuclides) plus the 33 radioactive primordial nuclides, for a total of 286 primordial nuclides. This number is subject to change if new shorter-lived primordials are identified on Earth.

One of the primordial nuclides is tantalum-180m, which is predicted to have a half-life in excess of 1015 years, but has never been observed to decay. The even longer half-life of 7.7 x 1024 years of tellurium-128 was measured by a unique method of detecting its radiogenic daughter xenon-128 and is the longest known experimentally measured half-life.[4] Another notable example is the only naturally occurring isotope of bismuth, bismuth-209, which has been predicted to be unstable with a very long half-life, but has been observed to decay. Because of their long half-lives, such isotopes are still found on Earth in various quantities, and together with the stable isotopes they are called primordial isotopes. All the primordial isotopes are given in order of their decreasing abundance on Earth.[c]. For a list of primordial nuclides in order of half-life, see list of nuclides.

118 chemical elements are known to exist. All elements to element 94 are found in nature, and the remainder of the discovered elements are artificially produced, with isotopes all known to be highly radioactive with relatively short half-lives (see below). The elements in this list are ordered according to the lifetime of their most stable isotope.[1] Of these, three elements (bismuth, thorium, and uranium) are primordial because they have half-lives long enough to still be found on the Earth,[d] while all the others are produced either by radioactive decay or are synthesized in laboratories and nuclear reactors. Only 13 of the 38 known-but-unstable elements (assuming the total number of elements is 118) have isotopes with a half-life of at least 100 years. Every known isotope of the remaining 25 elements is highly radioactive; these are used in academic research and sometimes in industry and medicine.[e] Some of the heavier elements in the periodic table may be revealed to have yet-undiscovered isotopes with longer lifetimes than those listed here.[f]

About 338 nuclides are found naturally on Earth. These comprise 253 stable isotopes, and with the addition of the 33 long-lived radioisotopes with half-lives longer than 100 million years, a total of 286 primordial nuclides, as noted above. The nuclides found naturally comprise not only the 286 primordials, but also include about 52 more short-lived isotopes (defined by a half-life less than 100 million years, too short to have survived from the formation of the Earth) that are daughters of primordial isotopes (such as radium from uranium); or else are made by energetic natural processes, such as carbon-14 made from atmospheric nitrogen by bombardment from cosmic rays.

Elements by number of primordial isotopes

An even number of protons or neutrons is more stable (higher binding energy) because of pairing effects, so even-even nuclides are much more stable than odd-odd. One effect is that there are few stable odd-odd nuclides: in fact only five are stable, with another four having half-lives longer than a billion years.

Another effect is to prevent beta decay of many even-even nuclides into another even-even nuclide of the same mass number but lower energy, because decay proceeding one step at a time would have to pass through an odd-odd nuclide of higher energy. (Double beta decay directly from even-even to even-even, skipping over an odd-odd nuclide, is only occasionally possible, and is a process so strongly hindered that it has a half-life greater than a billion times the age of the universe.) This makes for a larger number of stable even-even nuclides, up to three for some mass numbers, and up to seven for some atomic (proton) numbers and at least four for all stable even-Z elements beyond iron except for strontium.

Since a nucleus with an odd number of protons is relatively less stable, odd-numbered elements tend to have fewer stable isotopes. Of the 26 "monoisotopic" elements that have only a single stable isotope, all but one have an odd atomic number — the single exception being beryllium. In addition, no odd-numbered element has more than two stable isotopes, while every even-numbered element with stable isotopes, except for helium, beryllium, and carbon, has at least three.

Tables

The following tables give the elements with primordial nuclides, which means that the element may still be identified on Earth from natural sources, having been present since the Earth was formed out of the solar nebula. Thus, none are shorter-lived daughters of longer-lived parental primordials, such as radon. Two nuclides which have half-lives long enough to be primordial, but have not yet been conclusively observed as such (244Pu and 146Sm), have been excluded.

The tables of elements are sorted in order of decreasing number of nuclides associated with each element. (For a list sorted entirely in terms of half-lives of nuclides, with mixing of elements, see List of nuclides.) Stable and unstable (marked decays) nuclides are given, with symbols for unstable (radioactive) nuclides in italics. Note that the sorting does not quite give the elements purely in order of stable nuclides, since some elements have a larger number of long-lived unstable nuclides, which place them ahead of elements with a larger number of stable nuclides. By convention, nuclides are counted as "stable" if they have never been observed to decay by experiment or from observation of decay products (extremely long-lived nuclides unstable only in theory, such as tantalum-180m, are counted as stable).

The first table is for even-atomic numbered elements, which tend to have far more primordial nuclides, due to the stability conferred by proton-proton pairing. A second separate table is given for odd-atomic numbered elements, which tend to have far fewer stable and long-lived (primordial) unstable nuclides.

Primordial isotopes (in order of decreasing abundance on Earth[c]) of even-Z elements
Z
Element
Stable
[1]
Decays
[b][1]
unstable in italics[b]
odd neutron number in pink
50tin10 120
Sn
118
Sn
116
Sn
119
Sn
117
Sn
124
Sn
122
Sn
112
Sn
114
Sn
115
Sn
54xenon81 132
Xe
129
Xe
131
Xe
134
Xe
136
Xe
130
Xe
128
Xe
124
Xe
126
Xe
48cadmium62 114
Cd
112
Cd
111
Cd
110
Cd
113
Cd
116
Cd
106
Cd
108
Cd
52tellurium62 130
Te
128
Te
126
Te
125
Te
124
Te
122
Te
123
Te
120
Te
44ruthenium7 102
Ru
104
Ru
101
Ru
99
Ru
100
Ru
96
Ru
98
Ru
66dysprosium7 164
Dy
162
Dy
163
Dy
161
Dy
160
Dy
158
Dy
156
Dy
70ytterbium7 174
Yb
172
Yb
173
Yb
171
Yb
176
Yb
170
Yb
168
Yb
80mercury7 202
Hg
200
Hg
199
Hg
201
Hg
198
Hg
204
Hg
196
Hg
42molybdenum61 98
Mo
96
Mo
95
Mo
92
Mo
100
Mo
97
Mo
94
Mo
56barium61 138
Ba
137
Ba
136
Ba
135
Ba
134
Ba
132
Ba
130
Ba
64gadolinium61 158
Gd
160
Gd
156
Gd
157
Gd
155
Gd
154
Gd
152
Gd
76osmium61 192
Os
190
Os
189
Os
188
Os
187
Os
186
Os
184
Os
60neodymium52 142
Nd
144
Nd
146
Nd
143
Nd
145
Nd
148
Nd
150
Nd
62samarium52 152
Sm
154
Sm
147
Sm
149
Sm
148
Sm
150
Sm
144
Sm
46palladium6 106
Pd
108
Pd
105
Pd
110
Pd
104
Pd
102
Pd
68erbium6 166
Er
168
Er
167
Er
170
Er
164
Er
162
Er
20calcium51 40
Ca
44
Ca
42
Ca
48
Ca
43
Ca
46
Ca
34selenium51 80
Se
78
Se
76
Se
82
Se
77
Se
74
Se
36krypton51 84
Kr
86
Kr
82
Kr
83
Kr
80
Kr
78
Kr
72hafnium51 180
Hf
178
Hf
177
Hf
179
Hf
176
Hf
174
Hf
78platinum51 195
Pt
194
Pt
196
Pt
198
Pt
192
Pt
190
Pt
22titanium5 48
Ti
46
Ti
47
Ti
49
Ti
50
Ti
28nickel5 58
Ni
60
Ni
62
Ni
61
Ni
64
Ni
30zinc5 64
Zn
66
Zn
68
Zn
67
Zn
70
Zn
32germanium41 74
Ge
72
Ge
70
Ge
73
Ge
76
Ge
40zirconium41 90
Zr
94
Zr
92
Zr
91
Zr
96
Zr
74tungsten41 184
W
186
W
182
W
183
W
180
W
16sulfur4 32
S
34
S
33
S
36
S
24chromium4 52
Cr
53
Cr
50
Cr
54
Cr
26iron4 56
Fe
54
Fe
57
Fe
58
Fe
38strontium4 88
Sr
86
Sr
87
Sr
84
Sr
58cerium4 140
Ce
142
Ce
138
Ce
136
Ce
82lead4 208
Pb
206
Pb
207
Pb
204
Pb
8oxygen3 16
O
18
O
17
O
10neon3 20
Ne
22
Ne
21
Ne
12magnesium3 24
Mg
26
Mg
25
Mg
14silicon3 28
Si
29
Si
30
Si
18argon3 40
Ar
36
Ar
38
Ar
2helium24
He
3
He
6carbon2 12
C
13
C
92uranium02238
U
[d]
235
U
4beryllium19
Be
90thorium01232
Th
[d]
Primordial isotopes of odd-Z elements
Z
Element
Stab
Dec
unstable: italics
odd N in pink
19potassium2139
K
41
K
40
K
1hydrogen21
H
2
H
3lithium27
Li
6
Li
5boron211
B
10
B
7nitrogen214
N
15
N
17chlorine235
Cl
37
Cl
29copper263
Cu
65
Cu
31gallium269
Ga
71
Ga
35bromine279
Br
81
Br
47silver2107
Ag
109
Ag
51antimony2121
Sb
123
Sb
73tantalum2181
Ta
180m
Ta
77iridium2193
Ir
191
Ir
81thallium2205
Tl
203
Tl
23vanadium1151
V
50
V
37rubidium1185
Rb
87
Rb
49indium11115
In
113
In
57lanthanum11139
La
138
La
63europium11153
Eu
151
Eu
71lutetium11175
Lu
176
Lu
75rhenium11187
Re
185
Re
9fluorine119
F
11sodium123
Na
13aluminium127
Al
15phosphorus131
P
21scandium145
Sc
25manganese155
Mn
27cobalt159
Co
33arsenic175
As
39yttrium189
Y
41niobium193
Nb
45rhodium1103
Rh
53iodine1127
I
55caesium1133
Cs
59praseodymium1141
Pr
65terbium1159
Tb
67holmium1165
Ho
69thulium1169
Tm
79gold1197
Au
83bismuth01209
Bi

Elements with no primordial isotopes

No primordial isotopes
Longest lived isotope > 1 day
Z
Element
t1⁄2[g][1] Longest
lived
isotope
94plutonium8.08×107 a244
Pu
96curium1.56×107 a247
Cm
43technetium4.2×106 a98
Tc
[a]
93neptunium2.14×106 a237
Np
91protactinium32,760 a231
Pa
95americium7,370 a243
Am
88radium1,600 a226
Ra
97berkelium1,380 a247
Bk
98californium900 a251
Cf
84polonium125 a209
Po
89actinium21.772 a227
Ac
61promethium17.7 a145
Pm
[a]
99einsteinium1.293 a252
Es
[f]
100fermium100.5 d257
Fm
[f]
101mendelevium51.3 d258
Md
[f]
86radon3.823 d222
Rn
105dubnium29 h268
Db
[f]
No primordial isotopes
Longest lived isotope < 1 day
Z
Element
t1⁄2[g][1] Longest
lived
isotope
103lawrencium11 h266
Lr
[f]
85astatine8.1 h210
At
104rutherfordium5 h267
Rf
[f]
102nobelium58 min259
No
[f]
87francium22 min223
Fr
106seaborgium3.1 min269
Sg
[f]
111roentgenium2.1 min282
Rg
[f]
107bohrium61 s270
Bh
[f]
112copernicium29 s285
Cn
[f]
108hassium10 s270
Hs
[f]
110darmstadtium9.6 s281
Ds
[f]
109meitnerium8 s278
Mt
[f]
113nihonium8 s286
Nh
[f]
114flerovium1.9 s289
Fl
[f]
115moscovium0.8 s290
Mc
[f]
116livermorium53 ms293
Lv
[f]
117tennessine51 ms294
Ts
[f]
118oganesson0.7 ms294
Og
[f]

See also

Footnotes

  • a See stability of technetium isotopes for a detailed discussion as to why technetium and promethium have no stable isotopes.
  • b Isotopes that have a half-life of more than about 108 yr may still be found on Earth, but only those with half-lives above 7×108 yr (as of 235U) are found in appreciable quantities. The present list neglects a few isotopes with half-lives about 108 yr because they have been measured in tiny quantities on Earth. Uranium-234 with its half-life of 246,000 yr and natural isotopic abundance 0.0055% is a special case: it is a decay product of uranium-238 rather than a primordial nuclide.
  • c There are unstable isotopes with extremely long half-lives that are also found on Earth, and some of them are even more abundant than all the stable isotopes of a given element (for example, beta-active 187Re is twice as abundant as stable 185Re). Also, a bigger natural abundance of an isotope just implies that its formation was favored by the stellar nucleosynthesis process that produced the matter now constituting the Earth (and, of course, the rest of the Solar System) (see also Formation and evolution of the Solar System).
  • d While bismuth has only one primordial isotope, uranium has three isotopes that are found in nature in significant amounts (238
    U
    , 235
    U
    and 234
    U
    ; the first two are primordial, while 234U is radiogenic), and thorium has two (primordial 232
    Th
    and radiogenic 230
    Th
    ).
  • e See many different industrial and medical applications of radioactive elements in Radionuclide, Nuclear medicine, Common beta emitters, Commonly used gamma-emitting isotopes, Fluorine-18, Cobalt-60, Strontium-90, Technetium-99m, Iodine-123, Iodine-124, Promethium-147, Iridium-192 etc.
  • f For elements with a higher atomic number than californium (with Z>98), there might exist undiscovered isotopes that are more stable than the known ones.
  • g Legend: a=year, d=day, h=hour, min=minute, s=second.

References

  1. Sonzogni, Alejandro. "Interactive Chart of Nuclides". National Nuclear Data Center: Brookhaven National Laboratory. Retrieved 2008-06-06.
  2. Marcillac, Pierre de; Noël Coron; Gérard Dambier; Jacques Leblanc & Jean-Pierre Moalic (2003). "Experimental detection of α-particles from the radioactive decay of natural bismuth". Nature. 422 (6934): 876–878. Bibcode:2003Natur.422..876D. doi:10.1038/nature01541. PMID 12712201.
  3. Dumé, Belle (2003-04-23). "Bismuth breaks half-life record for alpha decay". Institute of Physics Publishing.
  4. "Archived copy". Archived from the original on 2011-09-28. Retrieved 2013-01-10. Novel Gas Research. Accessed April 26, 2009
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