Isotopes of tantalum

Natural tantalum (₇₃Ta) consists of two stable isotopes: ¹⁸¹Ta (99.988%) and ^180mTa (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 114.74 days, ¹⁸³Ta with a half-life of 5.1 days, and ¹⁷⁷Ta with a half-life of 56.46 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 ^182m2Ta with a half-life of 15.8 minutes. 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 tantalum, irradiated by the intense high-energy neutron flux of the weapon, would be transmuted into the radioactive isotope , producing about 1.12 MeV of gamma radiation per decay and significantly increasing the radioactivity of the weapon's fallout for months. Such a weapon is not known to have ever been built, tested, or used.

List of isotopes

|-id=Tantalum-155 | ¹⁵⁵Ta | style="text-align:center;" rowspan=103 | 73 | style="text-align:right" | 82 | 154.97425(32)# | | p | ¹⁵⁴Hf | 11/2− | | |-id=Tantalum-156 | rowspan=2|¹⁵⁶Ta | rowspan=2 style="text-align:right" | 83 | rowspan=2|155.97209(32)# | rowspan=2| | p (71%) | ¹⁵⁵Hf | rowspan=2|(2−) | rowspan=2| | rowspan=2| |- | β⁺ (29%) | ¹⁵⁶Hf |-id=Tantalum-156m | rowspan=2 style="text-indent:1em" | ^156mTa | rowspan=2 colspan="2" style="text-indent:2em" | | rowspan=2| | β⁺ (95.8%) | ¹⁵⁶Hf | rowspan=2|(9+) | rowspan=2| | rowspan=2| |- | p (4.2%) | ¹⁵⁵Hf |-id=Tantalum-157 | rowspan=2|¹⁵⁷Ta | rowspan=2 style="text-align:right" | 84 | rowspan=2|156.96823(16) | rowspan=2| | α (96.6%) | ¹⁵³Lu | rowspan=2|1/2+ | rowspan=2| | rowspan=2| |- | p (3.4%) | ¹⁵⁶Hf |-id=Tantalum-157m1 | style="text-indent:1em" | ^157m1Ta | colspan="2" style="text-indent:2em" | | | α | ¹⁵³Lu | 11/2− | | |-id=Tantalum-157m2 | style="text-indent:1em" | ^157m2Ta | colspan="2" style="text-indent:2em" | | | α | ¹⁵³Lu | 25/2−# | | |-id=Tantalum-158 | ¹⁵⁸Ta | style="text-align:right" | 85 | 157.96659(22)# | | α | ¹⁵⁴Lu | (2)− | | |-id=Tantalum-158m1 | style="text-indent:1em" | ^158m1Ta | colspan="2" style="text-indent:2em" | | | α (95%) | ¹⁵⁴Lu | (9)+ | | |-id=Tantalum-158m2 | rowspan=2 style="text-indent:1em" | ^158m2Ta | rowspan=2 colspan="2" style="text-indent:2em" | | rowspan=2| | IT (98.6%) | ¹⁵⁸Ta | rowspan=2|(19−) | rowspan=2| | rowspan=2| |- | α (1.4%) | ¹⁵⁴Lu |-id=Tantalum-159 | rowspan=2|¹⁵⁹Ta | rowspan=2 style="text-align:right" | 86 | rowspan=2|158.963028(21) | rowspan=2| | β⁺ (66%) | ¹⁵⁹Hf | rowspan=2|1/2+ | rowspan=2| | rowspan=2| |- | α (34%) | ¹⁵⁵Lu |-id=Tantalum-159m | rowspan=2 style="text-indent:1em" | ^159mTa | rowspan=2 colspan="2" style="text-indent:2em" | | rowspan=2| | α (55%) | ¹⁵⁵Lu | rowspan=2|11/2− | rowspan=2| | rowspan=2| |- | β⁺ (45%) | ¹⁵⁹Hf |-id=Tantalum-160 | ¹⁶⁰Ta | style="text-align:right" | 87 | 159.961542(58) | | α | ¹⁵⁶Lu | (2)− | | |-id=Tantalum-160m | style="text-indent:1em" | ^160mTa | colspan="2" style="text-indent:2em" | | | α | ¹⁵⁶Lu | (9,10)+ | | |-id=Tantalum-161 | ¹⁶¹Ta | style="text-align:right" | 88 | 160.958369(26) | | | | (1/2+) | | |-id=Tantalum-161m | rowspan=2 style="text-indent:1em" | ^161mTa | rowspan=2 colspan="2" style="text-indent:2em" | | rowspan=2| | β⁺ (93%) | ¹⁶¹Hf | rowspan=2|(11/2−) | rowspan=2| | rowspan=2| |- | α (7%) | ¹⁵⁷Lu |-id=Tantalum-162 | rowspan=2|¹⁶²Ta | rowspan=2 style="text-align:right" | 89 | rowspan=2|161.957293(68) | rowspan=2| | β⁺ (99.93%) | ¹⁶²Hf | rowspan=2|3−# | rowspan=2| | rowspan=2| |- | α (0.074%) | ¹⁵⁸Lu |-id=Tantalum-162m | style="text-indent:1em" | ^162mTa | colspan="2" style="text-indent:2em" | 120(50)#&nbsp;keV | | | | 7+# | | |-id=Tantalum-163 | ¹⁶³Ta | style="text-align:right" | 90 | 162.954337(41) | | β⁺ (99.8%) | ¹⁶³Hf | 1/2+ | | |-id=Tantalum-163m | style="text-indent:1em" | ^163mTa | colspan="2" style="text-indent:2em" | 138(18)#&nbsp;keV | | | | 9/2− | | |-id=Tantalum-164 | ¹⁶⁴Ta | style="text-align:right" | 91 | 163.953534(30) | | β⁺ | ¹⁶⁴Hf | (3+) | | |-id=Tantalum-165 | ¹⁶⁵Ta | style="text-align:right" | 92 | 164.950780(15) | | β⁺ | ¹⁶⁵Hf | (1/2+,3/2+) | | |-id=Tantalum-165m | style="text-indent:1em" | ^165mTa | colspan="2" style="text-indent:2em" | | | | | (9/2−) | | |-id=Tantalum-166 | ¹⁶⁶Ta | style="text-align:right" | 93 | 165.950512(30) | | β⁺ | ¹⁶⁶Hf | (2)+ | | |-id=Tantalum-167 | ¹⁶⁷Ta | style="text-align:right" | 94 | 166.948093(30) | | β⁺ | ¹⁶⁷Hf | (3/2+) | | |-id=Tantalum-168 | ¹⁶⁸Ta | style="text-align:right" | 95 | 167.948047(30) | | β⁺ | ¹⁶⁸Hf | (3+) | | |-id=Tantalum-169 | ¹⁶⁹Ta | style="text-align:right" | 96 | 168.946011(30) | | β⁺ | ¹⁶⁹Hf | (5/2+) | | |-id=Tantalum-170 | ¹⁷⁰Ta | style="text-align:right" | 97 | 169.946175(30) | | β⁺ | ¹⁷⁰Hf | (3+) | | |-id=Tantalum-171 | ¹⁷¹Ta | style="text-align:right" | 98 | 170.944476(30) | | β⁺ | ¹⁷¹Hf | (5/2+) | | |-id=Tantalum-172 | ¹⁷²Ta | style="text-align:right" | 99 | 171.944895(30) | | β⁺ | ¹⁷²Hf | (3+) | | |-id=Tantalum-173 | ¹⁷³Ta | style="text-align:right" | 100 | 172.943750(30) | | β⁺ | ¹⁷³Hf | 5/2− | | |-id=Tantalum-173m1 | style="text-indent:1em" | ^173m1Ta | colspan="2" style="text-indent:2em" | | | IT | ¹⁷³Ta | 9/2− | | |-id=Tantalum-173m2 | style="text-indent:1em" | ^173m2Ta | colspan="2" style="text-indent:2em" | | | IT | ¹⁷³Ta | 21/2− | | |-id=Tantalum-174 | ¹⁷⁴Ta | style="text-align:right" | 101 | 173.944454(30) | | β⁺ | ¹⁷⁴Hf | 3+ | | |-id=Tantalum-175 | ¹⁷⁵Ta | style="text-align:right" | 102 | 174.943737(30) | | β⁺ | ¹⁷⁵Hf | 7/2+ | | |-id=Tantalum-175m1 | style="text-indent:1em" | ^175m1Ta | colspan="2" style="text-indent:2em" | | | IT | ¹⁷⁵Ta | 9/2− | | |-id=Tantalum-175m2 | style="text-indent:1em" | ^175m2Ta | colspan="2" style="text-indent:2em" | | | IT | ¹⁷⁵Ta | (1/2+) | | |-id=Tantalum-175m3 | style="text-indent:1em" | ^175m3Ta | colspan="2" style="text-indent:2em" | | | IT | ¹⁷⁵Ta | 21/2− | | |-id=Tantalum-176 | ¹⁷⁶Ta | style="text-align:right" | 103 | 175.944857(33) | | β⁺ | ¹⁷⁶Hf | (1)− | | |-id=Tantalum-176m1 | style="text-indent:1em" | ^176m1Ta | colspan="2" style="text-indent:2em" | | | IT | ¹⁷⁶Ta | 7+ | | |-id=Tantalum-176m2 | style="text-indent:1em" | ^176m2Ta | colspan="2" style="text-indent:2em" | | | IT | ¹⁷⁶Ta | 14− | | |-id=Tantalum-176m3 | style="text-indent:1em" | ^176m3Ta | colspan="2" style="text-indent:2em" | | | IT | ¹⁷⁶Ta | 20− | | |-id=Tantalum-177 | ¹⁷⁷Ta | style="text-align:right" | 104 | 176.9444819(36) | | β⁺ | ¹⁷⁷Hf | 7/2+ | | |-id=Tantalum-177m1 | style="text-indent:1em" | ^177m1Ta | colspan="2" style="text-indent:2em" | | | IT | ¹⁷⁷Ta | 9/2− | | |-id=Tantalum-177m2 | style="text-indent:1em" | ^177m2Ta | colspan="2" style="text-indent:2em" | | | IT | ¹⁷⁷Ta | 5/2− | | |-id=Tantalum-177m3 | style="text-indent:1em" | ^177m3Ta | colspan="2" style="text-indent:2em" | | | IT | ¹⁷⁷Ta | 21/2− | | |-id=Tantalum-177m4 | style="text-indent:1em" | ^177m4Ta | colspan="2" style="text-indent:2em" | | | IT | ¹⁷⁷Ta | 49/2− | | |-id=Tantalum-178 | ¹⁷⁸Ta | style="text-align:right" | 105 | 177.945680(56)# | | β⁺ | ¹⁷⁸Hf | 7− | | |-id=Tantalum-178m1 | style="text-indent:1em" | ^178m1Ta | colspan="2" style="text-indent:2em" | 100(50)#&nbsp;keV | | β⁺ | ¹⁷⁸Hf | (1+) | | |-id=Tantalum-178m2 | style="text-indent:1em" | ^178m2Ta | colspan="2" style="text-indent:2em" | | | IT | ¹⁷⁸Ta | 15− | | |-id=Tantalum-178m3 | style="text-indent:1em" | ^178m3Ta | colspan="2" style="text-indent:2em" | | | IT | ¹⁷⁸Ta | 21− | | |-id=Tantalum-179 | ¹⁷⁹Ta | style="text-align:right" | 106 | 178.9459391(16) | | EC | ¹⁷⁹Hf | 7/2+ | | |-id=Tantalum-179m1 | style="text-indent:1em" | ^179m1Ta | colspan="2" style="text-indent:2em" | | | IT | ¹⁷⁹Ta | 9/2− | | |-id=Tantalum-179m2 | style="text-indent:1em" | ^179m2Ta | colspan="2" style="text-indent:2em" | | | IT | ¹⁷⁹Ta | 1/2+ | | |-id=Tantalum-179m3 | style="text-indent:1em" | ^179m3Ta | colspan="2" style="text-indent:2em" | | | IT | ¹⁷⁹Ta | 21/2− | | |-id=Tantalum-179m4 | style="text-indent:1em" | ^179m4Ta | colspan="2" style="text-indent:2em" | | | IT | ¹⁷⁹Ta | 25/2+ | | |-id=Tantalum-179m5 | style="text-indent:1em" | ^179m5Ta | colspan="2" style="text-indent:2em" | | | IT | ¹⁷⁹Ta | 23/2− | | |-id=Tantalum-179m6 | style="text-indent:1em" | ^179m6Ta | colspan="2" style="text-indent:2em" | | | IT | ¹⁷⁹Ta | 37/2+ | | |-id=Tantalum-180 | rowspan=2|¹⁸⁰Ta | rowspan=2 style="text-align:right" | 107 | rowspan=2|179.9474676(22) | rowspan=2| | EC (85%) | ¹⁸⁰Hf | rowspan=2|1+ | rowspan=2| | rowspan=2| |- | β^− (15%) | ¹⁸⁰W |-id=Tantalum-180m1 | style="text-indent:1em" | ^180m1Ta | colspan="2" style="text-indent:2em" | | colspan=3 style="text-align:center;" data-sort-value=999999999999999999999999|Observationally stable | 9− | 1.201(32)×10^{−4} | |-id=Tantalum-180m2 | style="text-indent:1em" | ^180m2Ta | colspan="2" style="text-indent:2em" | | | IT | | 15− | | |-id=Tantalum-180m3 | style="text-indent:1em" | ^180m3Ta | colspan="2" style="text-indent:2em" | | | IT | | (22−) | | |-id=Tantalum-180m4 | style="text-indent:1em" | ^180m4Ta | colspan="2" style="text-indent:2em" | | | IT | | (24+) | | |-id=Tantalum-181 | ¹⁸¹Ta | style="text-align:right" | 108 | 180.9479985(17) | colspan=3 style="text-align:center;" data-sort-value=999999999999999999999999|Observationally stable | 7/2+ | 0.9998799(32) | |-id=Tantalum-181m1 | style="text-indent:1em" | ^181m1Ta | colspan="2" style="text-indent:2em" | | | IT | ¹⁸¹Ta | 9/2− | | |-id=Tantalum-181m2 | style="text-indent:1em" | ^181m2Ta | colspan="2" style="text-indent:2em" | | | IT | ¹⁸¹Ta | 1/2+ | | |-id=Tantalum-181m3 | style="text-indent:1em" | ^181m3Ta | colspan="2" style="text-indent:2em" | | | IT | ¹⁸¹Ta | 19/2+# | | |-id=Tantalum-181m4 | style="text-indent:1em" | ^181m4Ta | colspan="2" style="text-indent:2em" | | | IT | ¹⁸¹Ta | 21/2− | | |-id=Tantalum-181m5 | style="text-indent:1em" | ^181m5Ta | colspan="2" style="text-indent:2em" | | | IT | ¹⁸¹Ta | 29/2− | | |-id=Tantalum-182 | ¹⁸²Ta | style="text-align:right" | 109 | 181.9501546(17) | | β^− | ¹⁸²W | 3− | | |-id=Tantalum-182m1 | style="text-indent:1em" | ^182m1Ta | colspan="2" style="text-indent:2em" | | | IT | ¹⁸²Ta | 5+ | | |-id=Tantalum-182m2 | style="text-indent:1em" | ^182m2Ta | colspan="2" style="text-indent:2em" | | | IT | ¹⁸²Ta | 10− | | |-id=Tantalum-183 | ¹⁸³Ta | style="text-align:right" | 110 | 182.9513754(17) | | β^− | ¹⁸³W | 7/2+ | | |-id=Tantalum-183m1 | style="text-indent:1em" | ^183m1Ta | colspan="2" style="text-indent:2em" | | | IT | ¹⁸³Ta | 9/2− | | |-id=Tantalum-183m2 | style="text-indent:1em" | ^183m2Ta | colspan="2" style="text-indent:2em" | | | IT | ¹⁸³Ta | (19/2+) | | |-id=Tantalum-184 | ¹⁸⁴Ta | style="text-align:right" | 111 | 183.954010(28) | | β^− | ¹⁸⁴W | (5−) | | |-id=Tantalum-185 | ¹⁸⁵Ta | style="text-align:right" | 112 | 184.955561(15) | | β^− | ¹⁸⁵W | (7/2+) | | |-id=Tantalum-185m1 | style="text-indent:1em" | ^185m1Ta | colspan="2" style="text-indent:2em" | | | IT | ¹⁸⁵Ta | (3/2+) | | |-id=Tantalum-185m2 | style="text-indent:1em" | ^185m2Ta | colspan="2" style="text-indent:2em" | | | IT | ¹⁸⁵Ta | 21/2− | | |-id=Tantalum-186 | ¹⁸⁶Ta | style="text-align:right" | 113 | 185.958553(64) | | β^− | ¹⁸⁶W | 3# | | |-id=Tantalum-186m | style="text-indent:1em" | ^186mTa | colspan="2" style="text-indent:2em" | | | | | 9+# | | |-id=Tantalum-187 | ¹⁸⁷Ta | style="text-align:right" | 114 | 186.960391(60) | | β^− | ¹⁸⁷W | (7/2+) | | |-id=Tantalum-187m1 | style="text-indent:1em" | ^187m1Ta | colspan="2" style="text-indent:2em" | | | IT | ¹⁸⁷Ta | (25/2−) | | |-id=Tantalum-187m2 | rowspan=2 style="text-indent:1em" | ^187m2Ta | rowspan=2 colspan="2" style="text-indent:2em" | | rowspan=2| | β^− | ^187mW | rowspan=2| 41/2+#<br/>[≥35/2] | rowspan=2| | rowspan=2| |- | IT | ^187m1Ta |-id=Tantalum-188 | ¹⁸⁸Ta | style="text-align:right" | 115 | 187.96360(22)# | | β^− | ¹⁸⁸W | (1−) | | |-id=Tantalum-188m1 | style="text-indent:1em" | ^188m1Ta | colspan="2" style="text-indent:2em" | | | | | (7−) | | |-id=Tantalum-188m2 | style="text-indent:1em" | ^188m2Ta | colspan="2" style="text-indent:2em" | | | IT | ¹⁸⁸Ta | 10+# | | |-id=Tantalum-189 | ¹⁸⁹Ta | style="text-align:right" | 116 | 188.96569(22)# | [>300&nbsp;ns] | β^− | ¹⁸⁹W | 7/2+# | | |-id=Tantalum-189m | style="text-indent:1em" | ^189mTa | colspan="2" style="text-indent:2em" | 1650(100)#&nbsp;keV | | IT | ¹⁸⁹Ta | 21/2−# | | |-id=Tantalum-190 | ¹⁹⁰Ta | style="text-align:right" | 117 | 189.96917(22)# | | β^− | ¹⁹⁰W | (3) | | |-id=Tantalum-191 | ¹⁹¹Ta | style="text-align:right" | 118 | 190.97153(32)# | [>300&nbsp;ns] | | | 7/2+# | | |-id=Tantalum-192 | ¹⁹²Ta | style="text-align:right" | 119 | 191.97520(43)# | | β^− | ¹⁹²W | (2) | | |-id=Tantalum-193 | ¹⁹³Ta | style="text-align:right" | 120 | 192.97766(43)# | [>300&nbsp;ns] | | | 7/2+# | | |-id=Tantalum-194 | ¹⁹⁴Ta | style="text-align:right" | 121 | 193.98161(54)# | [>300&nbsp;ns] | | | | |

Tantalum-180m

The nuclide (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 has a half-life of only 8 hours.

has sufficient energy to decay in three ways: isomeric transition to the ground state of , beta decay to , or electron capture to . 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 (290 quadrillion) years. The very slow decay of 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. Similar suppression of gamma or beta decay occurs for ^210mBi, a rather short-lived alpha emitter.

Because of this stability, is a primordial nuclide, the only naturally occurring nuclear isomer (excluding short-lived radiogenic and cosmogenic nuclides). It presents one of two apparent violations of the Mattauch isobar rule, the other involving tellurium-123. 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 k_BT = (i.e. a temperature of 300 million kelvin), the nuclear isomers are expected to be fully thermalized, meaning that ¹⁸⁰Ta is equilibrated between spin states and its overall half-life is predicted to be 11 hours.

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.

See also

Daughter products other than tantalum

• Isotopes of tungsten
• Isotopes of hafnium
• Isotopes of lutetium

References