List of elements by stability of isotopes

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

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.)

Isotope half-lives. Note that the darker more stable isotope region departs from the line of protons (Z) = neutrons (N), as the element number Z becomes larger

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,[citation needed] 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).[citation needed]

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[edit]

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[edit]

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
50 tin 10 120
Sn
118
Sn
116
Sn
119
Sn
117
Sn
124
Sn
122
Sn
112
Sn
114
Sn
115
Sn
54 xenon 8 1 132
Xe
129
Xe
131
Xe
134
Xe
136
Xe
130
Xe
128
Xe
124
Xe
126
Xe
48 cadmium 6 2 114
Cd
112
Cd
111
Cd
110
Cd
113
Cd
116
Cd
106
Cd
108
Cd
52 tellurium 6 2 130
Te
128
Te
126
Te
125
Te
124
Te
122
Te
123
Te
120
Te
44 ruthenium 7 102
Ru
104
Ru
101
Ru
99
Ru
100
Ru
96
Ru
98
Ru
66 dysprosium 7 164
Dy
162
Dy
163
Dy
161
Dy
160
Dy
158
Dy
156
Dy
70 ytterbium 7 174
Yb
172
Yb
173
Yb
171
Yb
176
Yb
170
Yb
168
Yb
80 mercury 7 202
Hg
200
Hg
199
Hg
201
Hg
198
Hg
204
Hg
196
Hg
42 molybdenum 6 1 98
Mo
96
Mo
95
Mo
92
Mo
100
Mo
97
Mo
94
Mo
56 barium 6 1 138
Ba
137
Ba
136
Ba
135
Ba
134
Ba
132
Ba
130
Ba
64 gadolinium 6 1 158
Gd
160
Gd
156
Gd
157
Gd
155
Gd
154
Gd
152
Gd
76 osmium 6 1 192
Os
190
Os
189
Os
188
Os
187
Os
186
Os
184
Os
60 neodymium 5 2 142
Nd
144
Nd
146
Nd
143
Nd
145
Nd
148
Nd
150
Nd
62 samarium 5 2 152
Sm
154
Sm
147
Sm
149
Sm
148
Sm
150
Sm
144
Sm
46 palladium 6 106
Pd
108
Pd
105
Pd
110
Pd
104
Pd
102
Pd
68 erbium 6 166
Er
168
Er
167
Er
170
Er
164
Er
162
Er
20 calcium 5 1 40
Ca
44
Ca
42
Ca
48
Ca
43
Ca
46
Ca
34 selenium 5 1 80
Se
78
Se
76
Se
82
Se
77
Se
74
Se
36 krypton 5 1 84
Kr
86
Kr
82
Kr
83
Kr
80
Kr
78
Kr
72 hafnium 5 1 180
Hf
178
Hf
177
Hf
179
Hf
176
Hf
174
Hf
78 platinum 5 1 195
Pt
194
Pt
196
Pt
198
Pt
192
Pt
190
Pt
22 titanium 5 48
Ti
46
Ti
47
Ti
49
Ti
50
Ti
28 nickel 5 58
Ni
60
Ni
62
Ni
61
Ni
64
Ni
30 zinc 5 64
Zn
66
Zn
68
Zn
67
Zn
70
Zn
32 germanium 4 1 74
Ge
72
Ge
70
Ge
73
Ge
76
Ge
40 zirconium 4 1 90
Zr
94
Zr
92
Zr
91
Zr
96
Zr
74 tungsten 4 1 184
W
186
W
182
W
183
W
180
W
16 sulfur 4 32
S
34
S
33
S
36
S
24 chromium 4 52
Cr
53
Cr
50
Cr
54
Cr
26 iron 4 56
Fe
54
Fe
57
Fe
58
Fe
38 strontium 4 88
Sr
86
Sr
87
Sr
84
Sr
58 cerium 4 140
Ce
142
Ce
138
Ce
136
Ce
82 lead 4 208
Pb
206
Pb
207
Pb
204
Pb
8 oxygen 3 16
O
18
O
17
O
10 neon 3 20
Ne
22
Ne
21
Ne
12 magnesium 3 24
Mg
26
Mg
25
Mg
14 silicon 3 28
Si
29
Si
30
Si
18 argon 3 40
Ar
36
Ar
38
Ar
2 helium 2 4
He
3
He
6 carbon 2 12
C
13
C
92 uranium 0 2 238
U
[d]
235
U
4 beryllium 1 9
Be
90 thorium 0 1 232
Th
[d]
Primordial isotopes of odd-Z elements
Z
Element
Stab
Dec
unstable: italics
odd N in pink
19 potassium 2 1 39
K
41
K
40
K
1 hydrogen 2 1
H
2
H
3 lithium 2 7
Li
6
Li
5 boron 2 11
B
10
B
7 nitrogen 2 14
N
15
N
17 chlorine 2 35
Cl
37
Cl
29 copper 2 63
Cu
65
Cu
31 gallium 2 69
Ga
71
Ga
35 bromine 2 79
Br
81
Br
47 silver 2 107
Ag
109
Ag
51 antimony 2 121
Sb
123
Sb
73 tantalum 2 181
Ta
180m
Ta
77 iridium 2 193
Ir
191
Ir
81 thallium 2 205
Tl
203
Tl
23 vanadium 1 1 51
V
50
V
37 rubidium 1 1 85
Rb
87
Rb
49 indium 1 1 115
In
113
In
57 lanthanum 1 1 139
La
138
La
63 europium 1 1 153
Eu
151
Eu
71 lutetium 1 1 175
Lu
176
Lu
75 rhenium 1 1 187
Re
185
Re
9 fluorine 1 19
F
11 sodium 1 23
Na
13 aluminium 1 27
Al
15 phosphorus 1 31
P
21 scandium 1 45
Sc
25 manganese 1 55
Mn
27 cobalt 1 59
Co
33 arsenic 1 75
As
39 yttrium 1 89
Y
41 niobium 1 93
Nb
45 rhodium 1 103
Rh
53 iodine 1 127
I
55 caesium 1 133
Cs
59 praseodymium 1 141
Pr
65 terbium 1 159
Tb
67 holmium 1 165
Ho
69 thulium 1 169
Tm
79 gold 1 197
Au
83 bismuth 0 1 209
Bi

Elements with no primordial isotopes[edit]

No primordial isotopes
Longest lived isotope in years/days
Z
Element
t1⁄2[g][1] Longest
lived
isotope
94 plutonium 8.00×107 a 244
Pu
96 curium 1.56×107 a 247
Cm
43 technetium 4.2×106 a 98
Tc
[a]
93 neptunium 2.144×106 a 237
Np
91 protactinium 32,760 a 231
Pa
95 americium 7,370 a 243
Am
88 radium 1,602 a 226
Ra
97 berkelium 1,380 a 247
Bk
98 californium 898 a 251
Cf
84 polonium 125 a 209
Po
89 actinium 21.77 a 227
Ac
61 promethium 17.7 a 145
Pm
[a]
99 einsteinium 1.29 a 252
Es
[f]
100 fermium 100.5 d 257
Fm
[f]
101 mendelevium 51.5 d 258
Md
[f]
86 radon 3.82 d 222
Rn
105 dubnium 1.3 d 268
Db
[f]
No primordial isotopes
Longest lived isotope in hour/min/sec
Z
Element
t1⁄2 of[g][1] Longest
lived
isotope
103 lawrencium 10 h 266
Lr
[f]
85 astatine 8.1 h 210
At
104 rutherfordium 1.3 h 267
Rf
[f]
102 nobelium 58 min 259
No
[f]
87 francium 22.0 min 223
Fr
106 seaborgium 3 min 269
Sg
[f]
111 roentgenium 2 min 282
Rg
[f]
107 bohrium 1 min 270
Bh
[f]
108 hassium 30 s 277
Hs
[f]
112 copernicium 30 s 285
Cn
[f]
110 darmstadtium 14 s 281
Ds
[f]
113 nihonium 8 s 286
Nh
[f]
109 meitnerium 4 s 278
Mt
[f]
114 flerovium 2 s 289
Fl
[f]
115 moscovium 8×10−1 s 290
Mc
[f]
116 livermorium 6×10−2 s 293
Lv
[f]
117 tennessine 5×10−2 s 294
Ts
[f]
118 oganesson 7×10−4 s 294
Og
[f]
Periodic table colored according to the number of stable isotopes. Elements with odd atomic numbers have at most one or two stable isotopes, while elements up to lead with even atomic numbers all have three or more stable isotopes, except for the first three: helium, beryllium, and carbon.
Periodic table with elements colored according to the half-life of their most stable isotope.
  Stable elements: Elements which contain at least one stable isotope;
  Slightly radioactive elements: the most stable isotope is very long-lived, with half-life of over two million years;
  Moderately radioactive elements: the most stable isotope has half-life between 800 and 34,000 years;
  Highly radioactive elements: the most stable isotope has half-life between one day and 103 years;
  Significantly radioactive elements: the most stable isotope has half-life between one minute and one day;
  Extremely radioactive elements: the most stable isotope has half-life less than a minute. Very little is known about these elements due to their extreme instability and radioactivity.

See also[edit]

Footnotes[edit]

  • 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[edit]

  1. ^ a b c d e f g h 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