Isotopes of protactinium
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Standard atomic weight (Ar, standard) |
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Protactinium (91Pa) has no stable isotopes. The three naturally occurring isotopes allow a standard mass to be given.
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 less than 1.6 days, and the majority of these have half-lives less than 1.8 seconds. This element also has three 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.
Actinides and fission products
Actinides and fission products by half-life | ||||||||
---|---|---|---|---|---|---|---|---|
Actinides[2] by decay chain | Half-life range (y) |
Fission products of 235U by yield[3] | ||||||
4n | 4n+1 | 4n+2 | 4n+3 | |||||
4.5–7% | 0.04–1.25% | <0.001% | ||||||
228Ra№ | 4–6 | † | 155Euþ | |||||
244Cmƒ | 241Puƒ | 250Cf | 227Ac№ | 10–29 | 90Sr | 85Kr | 113mCdþ | |
232Uƒ | 238Puƒ | 243Cmƒ | 29–97 | 137Cs | 151Smþ | 121mSn | ||
248Bk[4] | 249Cfƒ | 242mAmƒ | 141–351 |
No fission products | ||||
241Amƒ | 251Cfƒ[5] | 430–900 | ||||||
226Ra№ | 247Bk | 1.3 k – 1.6 k | ||||||
240Pu | 229Th | 246Cmƒ | 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 | |||||||
237Npƒ | 2.1 M – 6.5 M | 135Cs₡ | 107Pd | |||||
236U | 247Cmƒ | 15 M – 24 M | 129I₡ | |||||
244Pu№ | 80 M |
... nor beyond 15.7 M years[6] | ||||||
232Th№ | 238U№ | 235Uƒ№ | 0.7 G – 14.1 G | |||||
Legend for superscript symbols |
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
237Np | ||||||||||||||
↑ | ||||||||||||||
231U | ← | 232U | ↔ | 233U | ↔ | 234U | ↔ | 235U | ↔ | 236U | → | 237U | ||
↓ | ↑ | ↑ | ↑ | |||||||||||
231Pa | → | 232Pa | ← | 233Pa | → | 234Pa | ||||||||
↑ | ↑ | |||||||||||||
230Th | → | 231Th | ← | 232Th | → | 233Th | ||||||||
(Nuclides before a yellow background in italic have half-lives under 30 days; nuclides in bold have half-lives over 1,000,000 years; nuclides in red frames are fissile) |
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.
Protactinium-234
Protactinium-234 is a member of the uranium series with a half-life of 6.70 hours. It was discovered by Otto Hahn in 1921.[7]
Protactinium-234m
Protactinium-234m is a member of the uranium series with a half-life of 1.17 minutes. It was discovered in 1913 by Kazimierz Fajans and Oswald Helmuth Göhring, who named it brevium for its short half-life.[8] About 99.8% of decays of 234Th produce this isomer instead of the ground state (t1/2=6.70 hours).[8]
List of isotopes
nuclide symbol |
historic name |
Z(p) | N(n) | isotopic mass (u) |
half-life | decay mode(s)[9][n 1] |
daughter isotope(s)[n 2] |
nuclear spin and parity |
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 | |||||||||
SF (3×10−10%) | (various) | |||||||||
CD (10−12%) | 208Pb 23F | |||||||||
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
- 1 2 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
- ↑ Meija, J.; et al. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure and Applied Chemistry. 88 (3): 265–91. doi:10.1515/pac-2015-0305.
- ↑ 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 nuclides have half-lives of at least four years (the longest-lived nuclide 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.
- ↑ Milsted, J.; Friedman, A. M.; Stevens, C. M. (1965). "The alpha half-life of berkelium-247; a new long-lived isomer of berkelium-248". Nuclear Physics. 71 (2): 299. Bibcode:1965NucPh..71..299M. doi:10.1016/0029-5582(65)90719-4.
"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 nuclide with a half-life of at least four years before the "Sea of Instability".
- ↑ Excluding those "classically stable" nuclides 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.
- ↑ Fry, C., and M. Thoennessen. "Discovery of the Actinium, Thorium, Protactinium, and Uranium Isotopes." January 14, 2012. Accessed May 20, 2018. https://people.nscl.msu.edu/~thoennes/2009/ac-th-pa-u-adndt.pdf.
- 1 2 http://hpschapters.org/northcarolina/NSDS/Protactinium.pdf
- ↑ "Universal Nuclide Chart". nucleonica. (Registration required (help)).
- Isotope masses from:
- G. Audi; A. H. Wapstra; C. Thibault; J. Blachot; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). Nuclear Physics A. 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001. Archived from the original (PDF) on 2008-09-23.
- Isotopic compositions and standard atomic masses from:
- J. R. de Laeter; J. K. Böhlke; P. De Bièvre; H. Hidaka; H. S. Peiser; K. J. R. Rosman; P. D. P. Taylor (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry. 75 (6): 683–800. doi:10.1351/pac200375060683.
- M. E. Wieser (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry. 78 (11): 2051–2066. doi:10.1351/pac200678112051. Lay summary.
- Half-life, spin, and isomer data selected from the following sources. See editing notes on this article's talk page.
- G. Audi; A. H. Wapstra; C. Thibault; J. Blachot; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). Nuclear Physics A. 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001. Archived from the original (PDF) on 2008-09-23.
- National Nuclear Data Center. "NuDat 2.1 database". Brookhaven National Laboratory. Retrieved September 2005. Check date values in:
|accessdate=
(help) - N. E. Holden (2004). "Table of the Isotopes". In D. R. Lide. CRC Handbook of Chemistry and Physics (85th ed.). CRC Press. Section 11. ISBN 978-0-8493-0485-9.