Isotopes of tantalum

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Main isotopes of tantalum
Iso­tope Decay
abun­dance half-life (t1/2) mode pro­duct
177Ta syn 56.56 h ε 177Hf
178Ta syn 2.36 h ε 178Hf
179Ta syn 1.82 y ε 179Hf
180Ta syn 8.125 h ε 180Hf
β 180W
180mTa 0.012% stable
181Ta 99.988% stable
182Ta syn 114.43 d β 182W
183Ta syn 5.1 d β 183W
Standard atomic weight (Ar, standard)
  • 180.94788(2)[1]

Natural tantalum (73Ta) consists of two stable isotopes: 181Ta (99.988%) and 180m
Ta
(0.012%).

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 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.[2]

Tantalum-180m[edit]

The nuclide 180m
Ta
(m denotes a metastable state) has sufficient energy to decay in three ways: isomeric transition to the ground state of 180
Ta
, beta decay to 180
W
, and electron capture to 180
Hf
. 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 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.[3]

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). 180
Ta
has a half-life of only 8 hours. 180m
Ta
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.

As of October 3, 2016 the half life of 180mTa is calculated to be least 45x1015 (45 million billion) years.[4][5]

List of isotopes[edit]

nuclide
symbol
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
155
Ta
73 82 154.97459(54)# 13(4) µs
[12(+4−3) µs]
(11/2−)
156
Ta
73 83 155.97230(43)# 144(24) ms β+ (95.8%) 156Hf (2−)
p (4.2%) 155Hf
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) a 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 3] 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 4] 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
  1. ^ Abbreviations:
    EC: Electron capture
    IT: Isomeric transition
  2. ^ Bold for stable isotopes, bold italics for nearly-stable isotopes (half-life longer than the age of the universe)
  3. ^ 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 2.0×1016 years
  4. ^ Believed to undergo α decay to 177Lu

Notes[edit]

  • 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[edit]

  1. ^ Meija, J.; et al. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure Appl. Chem. 88 (3): 265–91. doi:10.1515/pac-2015-0305. 
  2. ^ D. T. Win; M. Al Masum (2003). "Weapons of Mass Destruction" (PDF). Assumption University Journal of Technology. 6 (4): 199–219. 
  3. ^ Quantum mechanics for engineers Leon van Dommelen, Florida State University
  4. ^ Conover, Emily (2016-10-03). "Rarest nucleus reluctant to decay". Retrieved 2016-10-05. 
  5. ^ Lehnert, Björn; Hult, Mikael; Lutter, Guillaume; Zuber, Kai (2016-09-13). "Search for the decay of nature's rarest isotope 180mTa". Physical Review C. 95. Bibcode:2017PhRvC..95d4306L. arXiv:1609.03725Freely accessible [nucl-ex]. doi:10.1103/PhysRevC.95.044306. 
  6. ^ "Universal Nuclide Chart". nucleonica. (Registration required (help)). 


Isotopes of hafnium Isotopes of tantalum Isotopes of tungsten
Table of nuclides