Isotopes of tantalum
Natural tantalum (73Ta) consists of two stable isotopes: 181Ta (99.988%) and 180m
Ta
(0.012%).
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Standard atomic weight Ar°(Ta) | |||||||||||||||||||||||||||||||||||||||||||||||||||||
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There are also 35 known artificial radioisotopes, the longest-lived of which are 179Ta with a half-life of 1.82 years, 182Ta with a half-life of 114.43 days, 183Ta with a half-life of 5.1 days, and 177Ta with a half-life of 56.56 hours. All other isotopes have half-lives under a day, most under an hour. There are also numerous isomers, the most stable of which (other than 180mTa) is 178m1Ta with a half-life of 2.36 hours. All isotopes and nuclear isomers of tantalum are either radioactive or observationally stable, meaning that they are predicted to be radioactive but no actual decay has been observed.
Tantalum has been proposed as a "salting" material for nuclear weapons (cobalt is another, better-known salting material). A jacket of 181Ta, irradiated by the intense high-energy neutron flux from an exploding thermonuclear weapon, would transmute into the radioactive isotope 182
Ta
with a half-life of 114.43 days and produce approximately 1.12 MeV of gamma radiation, significantly increasing the radioactivity of the weapon's fallout for several months. Such a weapon is not known to have ever been built, tested, or used.[4] While the conversion factor from absorbed dose (measured in Grays) to effective dose (measured in Sievert) for gamma rays is 1 while it is 50 for alpha radiation (i.e., a gamma dose of 1 Gray is equivalent to 1 Sievert whereas an alpha dose of 1 Gray is equivalent to 50 Sievert), gamma rays are only attenuated by shielding, not stopped. As such, alpha particles require incorporation to have an effect while gamma rays can have an effect via mere proximity. In military terms, this allows a gamma ray weapon to deny an area to either side as long as the dose is high enough, whereas radioactive contamination by alpha emitters which do not release significant amounts of gamma rays can be counteracted by ensuring the material is not incorporated.
List of isotopes
Nuclide [n 1] |
Z | N | Isotopic mass (Da) [n 2][n 3] |
Half-life [n 4] |
Decay mode [n 5] |
Daughter isotope [n 6][n 7] |
Spin and parity [n 8][n 4] |
Natural abundance (mole fraction) | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Excitation energy[n 4] | Normal proportion | Range of variation | |||||||||||||||||
155 Ta |
73 | 82 | 154.97459(54)# | 2.9+1.5 −1.1 ms[5] |
p | 154Hf | (11/2−) | ||||||||||||
155m Ta |
~323 keV | 12+4 −3 μs[6] |
p | 154Hf | 11/2−? | ||||||||||||||
156 Ta [7] |
73 | 83 | 155.97230(43)# | 106(4) ms | p (71%) | 155Hf | (2−) | ||||||||||||
β+ (29%) | 156Hf | ||||||||||||||||||
156m Ta |
102(7) keV | 0.36(4) s | p | 155Hf | 9+ | ||||||||||||||
157 Ta |
73 | 84 | 156.96819(22) | 10.1(4) ms | α (91%) | 153Lu | 1/2+ | ||||||||||||
β+ (9%) | 157Hf | ||||||||||||||||||
157m1 Ta |
22(5) keV | 4.3(1) ms | 11/2− | ||||||||||||||||
157m2 Ta |
1593(9) keV | 1.7(1) ms | α | 153Lu | (25/2−) | ||||||||||||||
158 Ta |
73 | 85 | 157.96670(22)# | 49(8) ms | α (96%) | 154Lu | (2−) | ||||||||||||
β+ (4%) | 158Hf | ||||||||||||||||||
158m Ta |
141(9) keV | 36.0(8) ms | α (93%) | 154Lu | (9+) | ||||||||||||||
IT | 158Ta | ||||||||||||||||||
β+ | 158Hf | ||||||||||||||||||
159 Ta |
73 | 86 | 158.963018(22) | 1.04(9) s | β+ (66%) | 159Hf | (1/2+) | ||||||||||||
α (34%) | 155Lu | ||||||||||||||||||
159m Ta |
64(5) keV | 514(9) ms | α (56%) | 155Lu | (11/2−) | ||||||||||||||
β+ (44%) | 159Hf | ||||||||||||||||||
160 Ta |
73 | 87 | 159.96149(10) | 1.70(20) s | α | 156Lu | (2#)− | ||||||||||||
β+ | 160Hf | ||||||||||||||||||
160m Ta |
310(90)# keV | 1.55(4) s | β+ (66%) | 160Hf | (9)+ | ||||||||||||||
α (34%) | 156Lu | ||||||||||||||||||
161 Ta |
73 | 88 | 160.95842(6)# | 3# s | β+ (95%) | 161Hf | 1/2+# | ||||||||||||
α (5%) | 157Lu | ||||||||||||||||||
161m Ta |
50(50)# keV | 2.89(12) s | 11/2−# | ||||||||||||||||
162 Ta |
73 | 89 | 161.95729(6) | 3.57(12) s | β+ (99.92%) | 162Hf | 3+# | ||||||||||||
α (.073%) | 158Lu | ||||||||||||||||||
163 Ta |
73 | 90 | 162.95433(4) | 10.6(18) s | β+ (99.8%) | 163Hf | 1/2+# | ||||||||||||
α (.2%) | 159Lu | ||||||||||||||||||
164 Ta |
73 | 91 | 163.95353(3) | 14.2(3) s | β+ | 164Hf | (3+) | ||||||||||||
165 Ta |
73 | 92 | 164.950773(19) | 31.0(15) s | β+ | 165Hf | 5/2−# | ||||||||||||
165m Ta |
60(30) keV | 9/2−# | |||||||||||||||||
166 Ta |
73 | 93 | 165.95051(3) | 34.4(5) s | β+ | 166Hf | (2)+ | ||||||||||||
167 Ta |
73 | 94 | 166.94809(3) | 1.33(7) min | β+ | 167Hf | (3/2+) | ||||||||||||
168 Ta |
73 | 95 | 167.94805(3) | 2.0(1) min | β+ | 168Hf | (2−,3+) | ||||||||||||
169 Ta |
73 | 96 | 168.94601(3) | 4.9(4) min | β+ | 169Hf | (5/2+) | ||||||||||||
170 Ta |
73 | 97 | 169.94618(3) | 6.76(6) min | β+ | 170Hf | (3)(+#) | ||||||||||||
171 Ta |
73 | 98 | 170.94448(3) | 23.3(3) min | β+ | 171Hf | (5/2−) | ||||||||||||
172 Ta |
73 | 99 | 171.94490(3) | 36.8(3) min | β+ | 172Hf | (3+) | ||||||||||||
173 Ta |
73 | 100 | 172.94375(3) | 3.14(13) h | β+ | 173Hf | 5/2− | ||||||||||||
174 Ta |
73 | 101 | 173.94445(3) | 1.14(8) h | β+ | 174Hf | 3+ | ||||||||||||
175 Ta |
73 | 102 | 174.94374(3) | 10.5(2) h | β+ | 175Hf | 7/2+ | ||||||||||||
176 Ta |
73 | 103 | 175.94486(3) | 8.09(5) h | β+ | 176Hf | (1)− | ||||||||||||
176m1 Ta |
103.0(10) keV | 1.1(1) ms | IT | 176Ta | (+) | ||||||||||||||
176m2 Ta |
1372.6(11)+X keV | 3.8(4) μs | (14−) | ||||||||||||||||
176m3 Ta |
2820(50) keV | 0.97(7) ms | (20−) | ||||||||||||||||
177 Ta |
73 | 104 | 176.944472(4) | 56.56(6) h | β+ | 177Hf | 7/2+ | ||||||||||||
177m1 Ta |
73.36(15) keV | 410(7) ns | 9/2− | ||||||||||||||||
177m2 Ta |
186.15(6) keV | 3.62(10) μs | 5/2− | ||||||||||||||||
177m3 Ta |
1355.01(19) keV | 5.31(25) μs | 21/2− | ||||||||||||||||
177m4 Ta |
4656.3(5) keV | 133(4) μs | 49/2− | ||||||||||||||||
178 Ta |
73 | 105 | 177.945778(16) | 9.31(3) min | β+ | 178Hf | 1+ | ||||||||||||
178m1 Ta |
100(50)# keV | 2.36(8) h | β+ | 178Hf | (7)− | ||||||||||||||
178m2 Ta |
1570(50)# keV | 59(3) ms | (15−) | ||||||||||||||||
178m3 Ta |
3000(50)# keV | 290(12) ms | (21−) | ||||||||||||||||
179 Ta |
73 | 106 | 178.9459295(23) | 1.82(3) y | EC | 179Hf | 7/2+ | ||||||||||||
179m1 Ta |
30.7(1) keV | 1.42(8) μs | (9/2)− | ||||||||||||||||
179m2 Ta |
520.23(18) keV | 335(45) ns | (1/2)+ | ||||||||||||||||
179m3 Ta |
1252.61(23) keV | 322(16) ns | (21/2−) | ||||||||||||||||
179m4 Ta |
1317.3(4) keV | 9.0(2) ms | IT | 179Ta | (25/2+) | ||||||||||||||
179m5 Ta |
1327.9(4) keV | 1.6(4) μs | (23/2−) | ||||||||||||||||
179m6 Ta |
2639.3(5) keV | 54.1(17) ms | (37/2+) | ||||||||||||||||
180 Ta |
73 | 107 | 179.9474648(24) | 8.152(6) h | EC (86%) | 180Hf | 1+ | ||||||||||||
β− (14%) | 180W | ||||||||||||||||||
180m1 Ta |
77.1(8) keV | Observationally stable[n 9][n 10] | 9− | 1.2(2)×10−4 | |||||||||||||||
180m2 Ta |
1452.40(18) keV | 31.2(14) μs | 15− | ||||||||||||||||
180m3 Ta |
3679.0(11) keV | 2.0(5) μs | (22−) | ||||||||||||||||
180m4 Ta |
4171.0+X keV | 17(5) μs | (23, 24, 25) | ||||||||||||||||
181 Ta |
73 | 108 | 180.9479958(20) | Observationally stable[n 11] | 7/2+ | 0.99988(2) | |||||||||||||
181m1 Ta |
6.238(20) keV | 6.05(12) μs | 9/2− | ||||||||||||||||
181m2 Ta |
615.21(3) keV | 18(1) μs | 1/2+ | ||||||||||||||||
181m3 Ta |
1485(3) keV | 25(2) μs | 21/2− | ||||||||||||||||
181m4 Ta |
2230(3) keV | 210(20) μs | 29/2− | ||||||||||||||||
182 Ta |
73 | 109 | 181.9501518(19) | 114.43(3) d | β− | 182W | 3− | ||||||||||||
182m1 Ta |
16.263(3) keV | 283(3) ms | IT | 182Ta | 5+ | ||||||||||||||
182m2 Ta |
519.572(18) keV | 15.84(10) min | 10− | ||||||||||||||||
183 Ta |
73 | 110 | 182.9513726(19) | 5.1(1) d | β− | 183W | 7/2+ | ||||||||||||
183m Ta |
73.174(12) keV | 107(11) ns | 9/2− | ||||||||||||||||
184 Ta |
73 | 111 | 183.954008(28) | 8.7(1) h | β− | 184W | (5−) | ||||||||||||
185 Ta |
73 | 112 | 184.955559(15) | 49.4(15) min | β− | 185W | (7/2+)# | ||||||||||||
185m Ta |
1308(29) keV | >1 ms | (21/2−) | ||||||||||||||||
186 Ta |
73 | 113 | 185.95855(6) | 10.5(3) min | β− | 186W | (2−,3−) | ||||||||||||
186m Ta |
1.54(5) min | ||||||||||||||||||
187 Ta |
73 | 114 | 186.96053(21)# | 2# min [>300 ns] |
β− | 187W | 7/2+# | ||||||||||||
188 Ta |
73 | 115 | 187.96370(21)# | 20# s [>300 ns] |
β− | 188W | |||||||||||||
189 Ta |
73 | 116 | 188.96583(32)# | 3# s [>300 ns] |
7/2+# | ||||||||||||||
190 Ta |
73 | 117 | 189.96923(43)# | 0.3# s | |||||||||||||||
This table header & footer: |
- mTa – Excited nuclear isomer.
- ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
- # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
- # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
-
Modes of decay:
EC: Electron capture IT: Isomeric transition p: Proton emission - Bold italics symbol as daughter – Daughter product is nearly stable.
- Bold symbol as daughter – Daughter product is stable.
- ( ) spin value – Indicates spin with weak assignment arguments.
- Only known observationally stable nuclear isomer, believed to decay by isomeric transition to 180Ta, β− decay to 180W, or electron capture to 180Hf with a half-life over 2.9×1017 years;[8] also theorized to undergo α decay to 176Lu
- One of the few (observationally) stable odd-odd nuclei
- Believed to undergo α decay to 177Lu
Tantalum-180m
The nuclide 180m
Ta
(m denotes a metastable state) is one of a very few nuclear isomers which are more stable than their ground states. Although it is not unique in this regard (this property is shared by bismuth-210m (210mBi) and americium-242m (242mAm), among other nuclides), it is exceptional in that it is observationally stable: no decay has ever been observed. In contrast, the ground state nuclide 180
Ta
has a half-life of only 8 hours.
180m
Ta
has sufficient energy to decay in three ways: isomeric transition to the ground state of 180
Ta
, beta decay to 180
W
, or electron capture to 180
Hf
. However, no radioactivity from any of these theoretically possible decay modes has ever been observed. As of 2023, the half-life of 180mTa is calculated from experimental observation to be at least 2.9×1017 (290 quadrillion) years.[8][9][10] The very slow decay of 180m
Ta
is attributed to its high spin (9 units) and the low spin of lower-lying states. Gamma or beta decay would require many units of angular momentum to be removed in a single step, so that the process would be very slow.[11]
Because of this stability, 180m
Ta
is a primordial nuclide, the only naturally occurring nuclear isomer (excluding short-lived radiogenic and cosmogenic nuclides). It is also the rarest primordial nuclide in the Universe observed for any element which has any stable isotopes. In an s-process stellar environment with a thermal energy kBT = 26 keV (i.e. a temperature of 300 million kelvin), the nuclear isomers are expected to be fully thermalized, meaning that 180Ta rapidly transitions between spin states and its overall half-life is predicted to be 11 hours.[12]
It is one of only five stable nuclides to have both an odd number of protons and an odd number of neutrons, the other four stable odd-odd nuclides being 2H, 6Li, 10B and 14N.[13]
References
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- Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
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- Uusitalo, J.; Davids, C. N.; Woods, P. J.; Seweryniak, D.; Sonzogni, A. A.; Batchelder, J. C.; Bingham, C. R.; Davinson, T.; deBoer, J.; Henderson, D. J.; Maier, H. J.; Ressler, J. J.; Slinger, R.; Walters, W. B. (1 June 1999). "Proton emission from the closed neutron shell nucleus 155 Ta". Physical Review C. 59 (6): R2975–R2978. Bibcode:1999PhRvC..59.2975U. doi:10.1103/PhysRevC.59.R2975. ISSN 0556-2813. Retrieved 12 June 2023.
- Darby, I. G.; Page, R. D.; Joss, D. T.; Bianco, L.; Grahn, T.; Judson, D. S.; Simpson, J.; Eeckhaudt, S.; Greenlees, P. T.; Jones, P. M.; Julin, R.; Juutinen, S.; Ketelhut, S.; Leino, M.; Leppänen, A.-P.; Nyman, M.; Rahkila, P.; Sarén, J.; Scholey, C.; Steer, A. N.; Uusitalo, J.; Venhart, M.; Ertürk, S.; Gall, B.; Hadinia, B. (20 June 2011). "Precision measurements of proton emission from the ground states of Ta 156 and Re 160". Physical Review C. 83 (6): 064320. Bibcode:2011PhRvC..83f4320D. doi:10.1103/PhysRevC.83.064320. ISSN 0556-2813. Retrieved 21 June 2023.
- Arnquist, I. J.; Avignone III, F. T.; Barabash, A. S.; Barton, C. J.; Bhimani, K. H.; Blalock, E.; Bos, B.; Busch, M.; Buuck, M.; Caldwell, T. S.; Christofferson, C. D.; Chu, P.-H.; Clark, M. L.; Cuesta, C.; Detwiler, J. A.; Efremenko, Yu.; Ejiri, H.; Elliott, S. R.; Giovanetti, G. K.; Goett, J.; Green, M. P.; Gruszko, J.; Guinn, I. S.; Guiseppe, V. E.; Haufe, C. R.; Henning, R.; Aguilar, D. Hervas; Hoppe, E. W.; Hostiuc, A.; Kim, I.; Kouzes, R. T.; Lannen V., T. E.; Li, A.; López-Castaño, J. M.; Massarczyk, R.; Meijer, S. J.; Meijer, W.; Oli, T. K.; Paudel, L. S.; Pettus, W.; Poon, A. W. P.; Radford, D. C.; Reine, A. L.; Rielage, K.; Rouyer, A.; Ruof, N. W.; Schaper, D. C.; Schleich, S. J.; Smith-Gandy, T. A.; Tedeschi, D.; Thompson, J. D.; Varner, R. L.; Vasilyev, S.; Watkins, S. L.; Wilkerson, J. F.; Wiseman, C.; Xu, W.; Yu, C.-H. (13 October 2023). "Constraints on the Decay of 180mTa". Phys. Rev. Lett. 131 (15) 152501. arXiv:2306.01965. doi:10.1103/PhysRevLett.131.152501.
- Conover, Emily (2016-10-03). "Rarest nucleus reluctant to decay". Science News. Retrieved 2016-10-05.
- Lehnert, Björn; Hult, Mikael; Lutter, Guillaume; Zuber, Kai (2017). "Search for the decay of nature's rarest isotope 180mTa". Physical Review C. 95 (4) 044306. arXiv:1609.03725. Bibcode:2017PhRvC..95d4306L. doi:10.1103/PhysRevC.95.044306. S2CID 118497863.
- Quantum mechanics for engineers Leon van Dommelen, Florida State University
- P. Mohr; F. Kaeppeler; R. Gallino (2007). "Survival of Nature's Rarest Isotope 180Ta under Stellar Conditions". Phys. Rev. C. 75 012802. arXiv:astro-ph/0612427. doi:10.1103/PhysRevC.75.012802. S2CID 44724195.
- Lide, David R., ed. (2002). Handbook of Chemistry & Physics (88th ed.). CRC. ISBN 978-0-8493-0486-6. OCLC 179976746. Archived from the original on 24 July 2017. Retrieved 2008-05-23.
- Isotope masses from:
- Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
- Isotopic compositions and standard atomic masses from:
- de Laeter, John Robert; Böhlke, John Karl; De Bièvre, Paul; Hidaka, Hiroshi; Peiser, H. Steffen; Rosman, Kevin J. R.; Taylor, Philip D. P. (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry. 75 (6): 683–800. doi:10.1351/pac200375060683.
- Wieser, Michael E. (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry. 78 (11): 2051–2066. doi:10.1351/pac200678112051.
- "News & Notices: Standard Atomic Weights Revised". International Union of Pure and Applied Chemistry. 19 October 2005.
- Half-life, spin, and isomer data selected from the following sources.
- Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
- National Nuclear Data Center. "NuDat 2.x database". Brookhaven National Laboratory.
- Holden, Norman E. (2004). "11. Table of the Isotopes". In Lide, David R. (ed.). CRC Handbook of Chemistry and Physics (85th ed.). Boca Raton, Florida: CRC Press. ISBN 978-0-8493-0485-9.