Isotopes of protactinium
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Actinides and fission products by half-life
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|---|---|---|---|---|---|---|---|---|
| Actinides[1] by decay chain | Half-life range (y) |
Fission products of 235U by yield[2] | ||||||
| 4n | 4n+1 | 4n+2 | 4n+3 | |||||
| 4.5–7% | 0.04–1.25% | <0.001% | ||||||
| 228Ra№ | 4–6 | † | 155Euþ | |||||
| 244Cm | 241Puƒ | 250Cf | 227Ac№ | 10–29 | 90Sr | 85Kr | 113mCdþ | |
| 232Uƒ | 238Pu№ | 243Cmƒ | 29–97 | 137Cs | 151Smþ | 121mSn | ||
| 248Bk[3] | 249Cfƒ | 242mAmƒ | 141–351 |
No fission products |
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| 241Amƒ | 251Cfƒ[4] | 430–900 | ||||||
| 226Ra№ | 247Bk | 1.3 k – 1.6 k | ||||||
| 240Pu | 229Th№ | 246Cm | 243Amƒ | 4.7 k – 7.4 k | ||||
| 245Cmƒ | 250Cm | 8.3 k – 8.5 k | ||||||
| 239Puƒ№ | 24.1 k | |||||||
| 230Th№ | 231Pa№ | 32 k – 76 k | ||||||
| 236Npƒ | 233Uƒ№ | 234U№ | 150 k – 250 k | ‡ | 99Tc₡ | 126Sn | ||
| 248Cm | 242Pu | 327 k – 375 k | 79Se₡ | |||||
| 1.53 M | 93Zr | |||||||
| 237Np№ | 2.1 M – 6.5 M | 135Cs₡ | 107Pd | |||||
| 236U№ | 247Cmƒ | 15 M – 24 M | 129I₡ | |||||
| 244Pu№ | 80 M |
... nor beyond 15.7 M years[5] |
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| 232Th№ | 238U№ | 235Uƒ№ | 0.7 G – 14.1 G | |||||
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Legend for superscript symbols |
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Protactinium (Pa) has no stable isotopes. There are three naturally occurring isotopes, allowing a standard mass to be given.
Relative atomic mass: 231.03588(2).
Twenty-nine radioisotopes of protactinium have been characterized, with the most stable being 231Pa with a half-life of 32,760 years, 233Pa with a half-life of 26.967 days, and 230Pa with a half-life of 17.4 days. All of the remaining radioactive isotopes have half-lives that are less than 1.6 days, and the majority of these have half-lives that are less than 1.8 seconds. This element also has 3 meta states, 217mPa (t1/2 1.15 milliseconds), 229mPa (t1/2 420 nanoseconds), and 234mPa (t1/2 1.17 minutes).
The only naturally occurring isotopes are 231Pa, which occurs as an intermediate decay product of 235U, 234Pa and 234mPa, both of which occur as intermediate decay products of 238U. 231Pa makes up nearly all natural protactinium.
The primary decay mode for isotopes of Pa lighter than (and including) the most stable isotope 231Pa is alpha decay, except for 228Pa to 230Pa, which primarily decay by electron capture to isotopes of thorium. The primary mode for the heavier isotopes is beta minus (β−) decay. The primary decay products of 231Pa and isotopes of protactinium lighter than and including 227Pa are isotopes of actinium and the primary decay products for the heavier isotopes of protactinium are isotopes of uranium.
Protactinium-230
Protactinium-230 has 139 neutrons and a half-life of 17.4 days. It undergoes beta-minus decay to 230U. It is not found in nature because its half-life is so short and it is not found in the decay chains of 235U, 238U, or 232Th. It has a mass of 230.034541 u.
Protactinium-231
| 230Th | → | 231Th | ← | 232Th | → | 233Th | (White actinides: t½<27d) | |||||||
| ↓ | ↓ | |||||||||||||
| 231Pa | → | 232Pa | ← | 233Pa | → | 234Pa | (Colored : t½>68y) | |||||||
| ↑ | ↓ | ↓ | ↓ | |||||||||||
| 231U | ← | 232U | ↔ | 233U | ↔ | 234U | ↔ | 235U | ↔ | 236U | → | 237U | ||
| ↓ | ↓ | ↓ | ↓ | |||||||||||
| (Fission products with t½<90y or t½>200ky) | 237Np | |||||||||||||
Protactinium-231 is the longest-lived isotope of protactinium, with a half-life of 32,760 years. In nature, it is found in trace amounts as part of the actinium series, which starts with the primordial isotope uranium-235; the equilibrium concentration in uranium ore is 46.55 231Pa per million 235U. In nuclear reactors, it is one of the few long-lived radioactive actinides produced as a byproduct of the projected thorium fuel cycle, as a result of (n,2n) reactions where a fast neutron removes a neutron from 232Th or 232U, and can also be destroyed by neutron capture though the cross section for this reaction is also low.
binding energy: 1759860 keV
beta decay energy: −382 keV
spin: 3/2−
mode of decay: alpha to 227Ac, also others
possible parent nuclides: beta from 231Th, EC from 231U, alpha from 235Np.
Protactinium-233
Protactinium-233 is also part of the thorium fuel cycle. It is an intermediate beta decay product between thorium-233 (produced from natural thorium-232 by neutron capture) and uranium-233 (the fissile fuel of the thorium cycle). Some thorium-cycle reactor designs try to protect Pa-233 from further neutron capture producing Pa-234 and U-234, which are not useful as fuel.
Table
| nuclide symbol |
historic name |
Z(p) | N(n) | isotopic mass (u) |
half-life | decay mode(s)[6][n 1] |
daughter isotope(s)[n 2] |
nuclear spin |
representative isotopic composition (mole fraction) |
range of natural variation (mole fraction) |
|---|---|---|---|---|---|---|---|---|---|---|
| excitation energy | ||||||||||
| 212Pa | 91 | 121 | 212.02320(8) | 8(5) ms [5.1(+61−19) ms] |
7+# | |||||
| 213Pa | 91 | 122 | 213.02111(8) | 7(3) ms [5.3(+40−16) ms] |
α | 209Ac | 9/2−# | |||
| 214Pa | 91 | 123 | 214.02092(8) | 17(3) ms | α | 210Ac | ||||
| 215Pa | 91 | 124 | 215.01919(9) | 14(2) ms | α | 211Ac | 9/2−# | |||
| 216Pa | 91 | 125 | 216.01911(8) | 105(12) ms | α (80%) | 212Ac | ||||
| β+ (20%) | 216Th | |||||||||
| 217Pa | 91 | 126 | 217.01832(6) | 3.48(9) ms | α | 213Ac | 9/2−# | |||
| 217mPa | 1860(7) keV | 1.08(3) ms | α | 213Ac | 29/2+# | |||||
| IT (rare) | 217Pa | |||||||||
| 218Pa | 91 | 127 | 218.020042(26) | 0.113(1) ms | α | 214Ac | ||||
| 219Pa | 91 | 128 | 219.01988(6) | 53(10) ns | α | 215Ac | 9/2− | |||
| β+ (5×10−9%) | 219Th | |||||||||
| 220Pa | 91 | 129 | 220.02188(6) | 780(160) ns | α | 216Ac | 1−# | |||
| 221Pa | 91 | 130 | 221.02188(6) | 4.9(8) µs | α | 217Ac | 9/2− | |||
| 222Pa | 91 | 131 | 222.02374(8)# | 3.2(3) ms | α | 218Ac | ||||
| 223Pa | 91 | 132 | 223.02396(8) | 5.1(6) ms | α | 219Ac | ||||
| β+ (.001%) | 223Th | |||||||||
| 224Pa | 91 | 133 | 224.025626(17) | 844(19) ms | α (99.9%) | 220Ac | 5−# | |||
| β+ (.1%) | 224Th | |||||||||
| 225Pa | 91 | 134 | 225.02613(8) | 1.7(2) s | α | 221Ac | 5/2−# | |||
| 226Pa | 91 | 135 | 226.027948(12) | 1.8(2) min | α (74%) | 222Ac | ||||
| β+ (26%) | 226Th | |||||||||
| 227Pa | 91 | 136 | 227.028805(8) | 38.3(3) min | α (85%) | 223Ac | (5/2−) | |||
| EC (15%) | 227Th | |||||||||
| 228Pa | 91 | 137 | 228.031051(5) | 22(1) h | β+ (98.15%) | 228Th | 3+ | |||
| α (1.85%) | 224Ac | |||||||||
| 229Pa | 91 | 138 | 229.0320968(30) | 1.50(5) d | EC (99.52%) | 229Th | (5/2+) | |||
| α (.48%) | 225Ac | |||||||||
| 229mPa | 11.6(3) keV | 420(30) ns | 3/2− | |||||||
| 230Pa | 91 | 139 | 230.034541(4) | 17.4(5) d | β+ (91.6%) | 230Th | (2−) | |||
| β− (8.4%) | 230U | |||||||||
| α (.00319%) | 226Ac | |||||||||
| 231Pa | Protoactinium | 91 | 140 | 231.0358840(24) | 3.276(11)×104 y | α | 227Ac | 3/2− | 1.0000[n 3] | |
| CD (1.34×10−9%) | 207Tl 24Ne |
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| SF (3×10−10%) | (various) | |||||||||
| CD (10−12%) | 208Pb 23F |
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| 232Pa | 91 | 141 | 232.038592(8) | 1.31(2) d | β− | 232U | (2−) | |||
| EC (.003%) | 232Th | |||||||||
| 233Pa | 91 | 142 | 233.0402473(23) | 26.975(13) d | β− | 233U | 3/2− | |||
| 234Pa | Uranium Z | 91 | 143 | 234.043308(5) | 6.70(5) h | β− | 234U | 4+ | Trace[n 4] | |
| SF (3×10−10%) | (various) | |||||||||
| 234mPa | Uranium X2 Brevium |
78(3) keV | 1.17(3) min | β− (99.83%) | 234U | (0−) | Trace[n 4] | |||
| IT (.16%) | 234Pa | |||||||||
| SF (10−10%) | (various) | |||||||||
| 235Pa | 91 | 144 | 235.04544(5) | 24.44(11) min | β− | 235U | (3/2−) | |||
| 236Pa | 91 | 145 | 236.04868(21) | 9.1(1) min | β− | 236U | 1(−) | |||
| β−, SF (6×10−8%) | (various) | |||||||||
| 237Pa | 91 | 146 | 237.05115(11) | 8.7(2) min | β− | 237U | (1/2+) | |||
| 238Pa | 91 | 147 | 238.05450(6) | 2.27(9) min | β− | 238U | (3−)# | |||
| β−, SF (2.6×10−6%) | (various) | |||||||||
| 239Pa | 91 | 148 | 239.05726(21)# | 1.8(5) h | β− | 239U | (3/2)(−#) | |||
| 240Pa | 91 | 149 | 240.06098(32)# | 2# min | β− | 240U | ||||
- ↑ Abbreviations:
CD: Cluster decay
EC: Electron capture
IT: Isomeric transition
SF: Spontaneous fission - ↑ Stable isotopes in bold
- ↑ Intermediate decay product of 235U
- ↑ 4.0 4.1 Intermediate decay product of 238U
Notes
- Values marked are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
- Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC, which use expanded uncertainties.
References
- ↑ Plus radium (element 88). While actually a sub-actinide, it immediately precedes actinium (89) and follows a three-element gap of instability after polonium (84) where no isotopes have half-lives of at least four years (the longest-lived isotope in the gap is radon-222 with a half life of less than four days). Radium's longest lived isotope, at 1,600 years, thus merits the element's inclusion here.
- ↑ Specifically from thermal neutron fission of U-235, e.g. in a typical nuclear reactor.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
"The isotopic analyses disclosed a species of mass 248 in constant abundance in three samples analysed over a period of about 10 months. This was ascribed to an isomer of Bk248 with a half-life greater than 9 y. No growth of Cf248 was detected, and a lower limit for the β− half-life can be set at about 104 y. No alpha activity attributable to the new isomer has been detected; the alpha half-life is probably greater than 300 y." - ↑ This is the heaviest isotope with a half-life of at least four years before the "Sea of Instability".
- ↑ Excluding those "classically stable" isotopes with half-lives significantly in excess of 232Th; e.g., while 113mCd has a half-life of only fourteen years, that of 113Cd is nearly eight quadrillion years.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- Isotope masses from:
- Lua error in package.lua at line 80: module 'strict' not found.
- Isotopic compositions and standard atomic masses from:
- Lua error in package.lua at line 80: module 'strict' not found.
- Lua error in package.lua at line 80: module 'strict' not found.
- Half-life, spin, and isomer data selected from the following sources. See editing notes on this article's talk page.
- Lua error in package.lua at line 80: module 'strict' not found.
- Lua error in package.lua at line 80: module 'strict' not found.
- Lua error in package.lua at line 80: module 'strict' not found.
| Isotopes of thorium | Isotopes of protactinium | Isotopes of uranium |
| Table of nuclides | ||
| Isotopes of the chemical elements | |||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 H |
2 He |
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| 3 Li |
4 Be |
5 B |
6 C |
7 N |
8 O |
9 F |
10 Ne |
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| 11 Na |
12 Mg |
13 Al |
14 Si |
15 P |
16 S |
17 Cl |
18 Ar |
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| 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 |
| 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 |
| 55 Cs |
56 Ba |
 |
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 |
| 87 Fr |
88 Ra |
 |
104 Rf |
105 Db |
106 Sg |
107 Bh |
108 Hs |
109 Mt |
110 Ds |
111 Rg |
112 Cn |
113 Uut |
114 Fl |
115 Uup |
116 Lv |
117 Uus |
118 Uuo |
 |
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 |
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|
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 |
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