Isotopes of tantalum
Natural tantalum (Ta) consists of two stable isotopes: 181Ta (99.988%) and 180mTa (0.012%).
The latter nuclide 180mTa (m denotes a metastable state) has sufficient energy to decay in three ways: isomeric transition to the ground state of 180Ta, beta decay to 180W, and electron capture to 180Hf. However, no radioactivity from any decay mode of this nuclear isomer has ever been observed. Only a lower limit on its half-life of over 1015 years has been set, by observation. The very slow decay of 180mTa 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.[1]
The very unusual nature of 180mTa is that the ground state of this isotope is less stable than the isomer. The same property is exhibited in americium-242m (242mAm). 180Ta has a half-life of only 8 hours. 180mTa is the only naturally occurring nuclear isomer (excluding radiogenic and cosmogenic short-living nuclides). It is also the rarest primordial nuclide in the Universe observed for any element that has any stable isotopes.
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.
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 182Ta 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.[2]
Tantalum has a relative atomic massof 180.94788(2).
Table
| nuclide symbol |
Z(p) | N(n) | isotopic mass (u) |
half-life | decay mode(s)[3][n 1] |
daughter isotope(s)[n 2] |
nuclear spin |
representative isotopic composition (mole fraction) |
range of natural variation (mole fraction) |
|---|---|---|---|---|---|---|---|---|---|
| excitation energy | |||||||||
| 155Ta | 73 | 82 | 154.97459(54)# | 13(4) µs [12(+4−3) µs] |
(11/2−) | ||||
| 156Ta | 73 | 83 | 155.97230(43)# | 144(24) ms | β+ (95.8%) | 156Hf | (2−) | ||
| p (4.2%) | 155Hf | ||||||||
| 156mTa | 102(7) keV | 0.36(4) s | p | 155Hf | 9+ | ||||
| 157Ta | 73 | 84 | 156.96819(22) | 10.1(4) ms | α (91%) | 153Lu | 1/2+ | ||
| β+ (9%) | 157Hf | ||||||||
| 157m1Ta | 22(5) keV | 4.3(1) ms | 11/2− | ||||||
| 157m2Ta | 1593(9) keV | 1.7(1) ms | α | 153Lu | (25/2−) | ||||
| 158Ta | 73 | 85 | 157.96670(22)# | 49(8) ms | α (96%) | 154Lu | (2−) | ||
| β+ (4%) | 158Hf | ||||||||
| 158mTa | 141(9) keV | 36.0(8) ms | α (93%) | 154Lu | (9+) | ||||
| IT | 158Ta | ||||||||
| β+ | 158Hf | ||||||||
| 159Ta | 73 | 86 | 158.963018(22) | 1.04(9) s | β+ (66%) | 159Hf | (1/2+) | ||
| α (34%) | 155Lu | ||||||||
| 159mTa | 64(5) keV | 514(9) ms | α (56%) | 155Lu | (11/2−) | ||||
| β+ (44%) | 159Hf | ||||||||
| 160Ta | 73 | 87 | 159.96149(10) | 1.70(20) s | α | 156Lu | (2#)− | ||
| β+ | 160Hf | ||||||||
| 160mTa | 310(90)# keV | 1.55(4) s | β+ (66%) | 160Hf | (9)+ | ||||
| α (34%) | 156Lu | ||||||||
| 161Ta | 73 | 88 | 160.95842(6)# | 3# s | β+ (95%) | 161Hf | 1/2+# | ||
| α (5%) | 157Lu | ||||||||
| 161mTa | 50(50)# keV | 2.89(12) s | 11/2−# | ||||||
| 162Ta | 73 | 89 | 161.95729(6) | 3.57(12) s | β+ (99.92%) | 162Hf | 3+# | ||
| α (.073%) | 158Lu | ||||||||
| 163Ta | 73 | 90 | 162.95433(4) | 10.6(18) s | β+ (99.8%) | 163Hf | 1/2+# | ||
| α (.2%) | 159Lu | ||||||||
| 164Ta | 73 | 91 | 163.95353(3) | 14.2(3) s | β+ | 164Hf | (3+) | ||
| 165Ta | 73 | 92 | 164.950773(19) | 31.0(15) s | β+ | 165Hf | 5/2−# | ||
| 165mTa | 60(30) keV | 9/2−# | |||||||
| 166Ta | 73 | 93 | 165.95051(3) | 34.4(5) s | β+ | 166Hf | (2)+ | ||
| 167Ta | 73 | 94 | 166.94809(3) | 1.33(7) min | β+ | 167Hf | (3/2+) | ||
| 168Ta | 73 | 95 | 167.94805(3) | 2.0(1) min | β+ | 168Hf | (2−,3+) | ||
| 169Ta | 73 | 96 | 168.94601(3) | 4.9(4) min | β+ | 169Hf | (5/2+) | ||
| 170Ta | 73 | 97 | 169.94618(3) | 6.76(6) min | β+ | 170Hf | (3)(+#) | ||
| 171Ta | 73 | 98 | 170.94448(3) | 23.3(3) min | β+ | 171Hf | (5/2−) | ||
| 172Ta | 73 | 99 | 171.94490(3) | 36.8(3) min | β+ | 172Hf | (3+) | ||
| 173Ta | 73 | 100 | 172.94375(3) | 3.14(13) h | β+ | 173Hf | 5/2− | ||
| 174Ta | 73 | 101 | 173.94445(3) | 1.14(8) h | β+ | 174Hf | 3+ | ||
| 175Ta | 73 | 102 | 174.94374(3) | 10.5(2) h | β+ | 175Hf | 7/2+ | ||
| 176Ta | 73 | 103 | 175.94486(3) | 8.09(5) h | β+ | 176Hf | (1)− | ||
| 176m1Ta | 103.0(10) keV | 1.1(1) ms | IT | 176Ta | (+) | ||||
| 176m2Ta | 1372.6(11)+X keV | 3.8(4) µs | (14−) | ||||||
| 176m3Ta | 2820(50) keV | 0.97(7) ms | (20−) | ||||||
| 177Ta | 73 | 104 | 176.944472(4) | 56.56(6) h | β+ | 177Hf | 7/2+ | ||
| 177m1Ta | 73.36(15) keV | 410(7) ns | 9/2− | ||||||
| 177m2Ta | 186.15(6) keV | 3.62(10) µs | 5/2− | ||||||
| 177m3Ta | 1355.01(19) keV | 5.31(25) µs | 21/2− | ||||||
| 177m4Ta | 4656.3(5) keV | 133(4) µs | 49/2− | ||||||
| 178Ta | 73 | 105 | 177.945778(16) | 9.31(3) min | β+ | 178Hf | 1+ | ||
| 178m1Ta | 100(50)# keV | 2.36(8) h | β+ | 178Hf | (7)− | ||||
| 178m2Ta | 1570(50)# keV | 59(3) ms | (15−) | ||||||
| 178m3Ta | 3000(50)# keV | 290(12) ms | (21−) | ||||||
| 179Ta | 73 | 106 | 178.9459295(23) | 1.82(3) a | EC | 179Hf | 7/2+ | ||
| 179m1Ta | 30.7(1) keV | 1.42(8) µs | (9/2)− | ||||||
| 179m2Ta | 520.23(18) keV | 335(45) ns | (1/2)+ | ||||||
| 179m3Ta | 1252.61(23) keV | 322(16) ns | (21/2−) | ||||||
| 179m4Ta | 1317.3(4) keV | 9.0(2) ms | IT | 179Ta | (25/2+) | ||||
| 179m5Ta | 1327.9(4) keV | 1.6(4) µs | (23/2−) | ||||||
| 179m6Ta | 2639.3(5) keV | 54.1(17) ms | (37/2+) | ||||||
| 180Ta | 73 | 107 | 179.9474648(24) | 8.152(6) h | EC (86%) | 180Hf | 1+ | ||
| β− (14%) | 180W | ||||||||
| 180m1Ta | 77.1(8) keV | Observationally stable[n 3] | 9− | 1.2(2)×10−4 | |||||
| 180m2Ta | 1452.40(18) keV | 31.2(14) µs | 15− | ||||||
| 180m3Ta | 3679.0(11) keV | 2.0(5) µs | (22−) | ||||||
| 180m4Ta | 4171.0+X keV | 17(5) µs | (23,24,25) | ||||||
| 181Ta | 73 | 108 | 180.9479958(20) | Observationally stable[n 4] | 7/2+ | 0.99988(2) | |||
| 181m1Ta | 6.238(20) keV | 6.05(12) µs | 9/2− | ||||||
| 181m2Ta | 615.21(3) keV | 18(1) µs | 1/2+ | ||||||
| 181m3Ta | 1485(3) keV | 25(2) µs | 21/2− | ||||||
| 181m4Ta | 2230(3) keV | 210(20) µs | 29/2− | ||||||
| 182Ta | 73 | 109 | 181.9501518(19) | 114.43(3) d | β− | 182W | 3− | ||
| 182m1Ta | 16.263(3) keV | 283(3) ms | IT | 182Ta | 5+ | ||||
| 182m2Ta | 519.572(18) keV | 15.84(10) min | 10− | ||||||
| 183Ta | 73 | 110 | 182.9513726(19) | 5.1(1) d | β− | 183W | 7/2+ | ||
| 183mTa | 73.174(12) keV | 107(11) ns | 9/2− | ||||||
| 184Ta | 73 | 111 | 183.954008(28) | 8.7(1) h | β− | 184W | (5−) | ||
| 185Ta | 73 | 112 | 184.955559(15) | 49.4(15) min | β− | 185W | (7/2+)# | ||
| 185mTa | 1308(29) keV | >1 ms | (21/2−) | ||||||
| 186Ta | 73 | 113 | 185.95855(6) | 10.5(3) min | β− | 186W | (2−,3−) | ||
| 186mTa | 1.54(5) min | ||||||||
| 187Ta | 73 | 114 | 186.96053(21)# | 2# min [>300 ns] |
β− | 187W | 7/2+# | ||
| 188Ta | 73 | 115 | 187.96370(21)# | 20# s [>300 ns] |
β− | 188W | |||
| 189Ta | 73 | 116 | 188.96583(32)# | 3# s [>300 ns] |
7/2+# | ||||
| 190Ta | 73 | 117 | 189.96923(43)# | 0.3# s | |||||
- ↑ Abbreviations:
EC: Electron capture
IT: Isomeric transition - ↑ Bold for stable isotopes, bold italics for nearly-stable isotopes (half-life longer than the age of the universe)
- ↑ 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 1.2×1015 years
- ↑ Believed to undergo α decay to 177Lu
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
- ↑ Quantum mechanics for engineers Leon van Dommelen, Florida State University
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
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- Isotope masses from:
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- Isotopic compositions and standard atomic masses from:
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- Half-life, spin, and isomer data selected from the following sources. See editing notes on this article's talk page.
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| Isotopes of hafnium | Isotopes of tantalum | Isotopes of tungsten |
| Table of nuclides | ||
| Isotopes of the chemical elements | |||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 H |
2 He |
||||||||||||||||
| 3 Li |
4 Be |
5 B |
6 C |
7 N |
8 O |
9 F |
10 Ne |
||||||||||
| 11 Na |
12 Mg |
13 Al |
14 Si |
15 P |
16 S |
17 Cl |
18 Ar |
||||||||||
| 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 |
||
|
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 |
||
