Natural

tantalum Tantalum is a chemical element with the symbol Ta and atomic number 73. Previously known as ''tantalium'', it is named after Tantalus, a villain in Greek mythology. Tantalum is a very hard, ductile, lustrous, blue-gray transition metal that ...

(₇₃Ta) consists of two stable

isotope Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers ( mass num ...

s: ¹⁸¹Ta (99.988%) and (0.012%). There are also 35 known artificial

radioisotope A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation; transferr ...

s, 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 A nuclear isomer is a metastable state of an atomic nucleus, in which one or more nucleons (protons or neutrons) occupy higher energy levels than in the ground state of the same nucleus. "Metastable" describes nuclei whose excited states have h ...

of tantalum are either radioactive or

observationally stable Stable nuclides are nuclides that are not radioactive and so (unlike radionuclides) do not spontaneously undergo radioactive decay. When such nuclides are referred to in relation to specific elements, they are usually termed stable isotopes. Th ...

, 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 weapon A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission (fission bomb) or a combination of fission and fusion reactions ( thermonuclear bomb), producing a nuclear explosion. Both bomb ...

s (

cobalt Cobalt is a chemical element with the symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. The free element, p ...

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 with a

half-life Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable ...

of 114.43 days and produce approximately 1.12 MeV of

gamma radiation A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically s ...

, significantly increasing the radioactivity of the weapon's

fallout Nuclear fallout is the residual radioactive material propelled into the upper atmosphere following a nuclear blast, so called because it "falls out" of the sky after the explosion and the shock wave has passed. It commonly refers to the radioac ...

for several months. Such a weapon is not known to have ever been built, tested, or used. While the conversion factor from

absorbed dose Absorbed dose is a dose quantity which is the measure of the energy deposited in matter by ionizing radiation per unit mass. Absorbed dose is used in the calculation of dose uptake in living tissue in both radiation protection (reduction of har ...

(measured in Grays) to effective dose (measured in

Sievert The sievert (symbol: SvNot be confused with the sverdrup or the svedberg, two non-SI units that sometimes use the same symbol.) is a unit in the International System of Units (SI) intended to represent the stochastic health risk of ionizing rad ...

) 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 Radioactive contamination, also called radiological pollution, is the deposition of, or presence of radioactive substances on surfaces or within solids, liquids, or gases (including the human body), where their presence is unintended or undesirab ...

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

, - , , style="text-align:right" , 73 , style="text-align:right" , 82 , 154.97459(54)# , 13(4) µs
2(+4−3) µs, , , (11/2−) , , , - , rowspan=2, , rowspan=2 style="text-align:right" , 73 , rowspan=2 style="text-align:right" , 83 , rowspan=2, 155.97230(43)# , rowspan=2, 144(24) ms , β⁺ (95.8%) , ¹⁵⁶Hf , rowspan=2, (2−) , rowspan=2, , rowspan=2, , - , p (4.2%) , ¹⁵⁵Hf , - , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , 102(7) keV , 0.36(4) s , p , ¹⁵⁵Hf , 9+ , , , - , rowspan=2, , rowspan=2 style="text-align:right" , 73 , rowspan=2 style="text-align:right" , 84 , rowspan=2, 156.96819(22) , rowspan=2, 10.1(4) ms , α (91%) , ¹⁵³Lu , rowspan=2, 1/2+ , rowspan=2, , rowspan=2, , - , β⁺ (9%) , ¹⁵⁷Hf , - , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , 22(5) keV , 4.3(1) ms , , , 11/2− , , , - , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , 1593(9) keV , 1.7(1) ms , α , ¹⁵³Lu , (25/2−) , , , - , rowspan=2, , rowspan=2 style="text-align:right" , 73 , rowspan=2 style="text-align:right" , 85 , rowspan=2, 157.96670(22)# , rowspan=2, 49(8) ms , α (96%) , ¹⁵⁴Lu , rowspan=2, (2−) , rowspan=2, , rowspan=2, , - , β⁺ (4%) , ¹⁵⁸Hf , - , rowspan=3 style="text-indent:1em" , , rowspan=3 colspan="3" style="text-indent:2em" , 141(9) keV , rowspan=3, 36.0(8) ms , α (93%) , ¹⁵⁴Lu , rowspan=3, (9+) , rowspan=3, , rowspan=3, , - , IT , ¹⁵⁸Ta , - , β⁺ , ¹⁵⁸Hf , - , rowspan=2, , rowspan=2 style="text-align:right" , 73 , rowspan=2 style="text-align:right" , 86 , rowspan=2, 158.963018(22) , rowspan=2, 1.04(9) s , β⁺ (66%) , ¹⁵⁹Hf , rowspan=2, (1/2+) , rowspan=2, , rowspan=2, , - , α (34%) , ¹⁵⁵Lu , - , rowspan=2 style="text-indent:1em" , , rowspan=2 colspan="3" style="text-indent:2em" , 64(5) keV , rowspan=2, 514(9) ms , α (56%) , ¹⁵⁵Lu , rowspan=2, (11/2−) , rowspan=2, , rowspan=2, , - , β⁺ (44%) , ¹⁵⁹Hf , - , rowspan=2, , rowspan=2 style="text-align:right" , 73 , rowspan=2 style="text-align:right" , 87 , rowspan=2, 159.96149(10) , rowspan=2, 1.70(20) s , α , ¹⁵⁶Lu , rowspan=2, (2#)− , rowspan=2, , rowspan=2, , - , β⁺ , ¹⁶⁰Hf , - , rowspan=2 style="text-indent:1em" , , rowspan=2 colspan="3" style="text-indent:2em" , 310(90)# keV , rowspan=2, 1.55(4) s , β⁺ (66%) , ¹⁶⁰Hf , rowspan=2, (9)+ , rowspan=2, , rowspan=2, , - , α (34%) , ¹⁵⁶Lu , - , rowspan=2, , rowspan=2 style="text-align:right" , 73 , rowspan=2 style="text-align:right" , 88 , rowspan=2, 160.95842(6)# , rowspan=2, 3# s , β⁺ (95%) , ¹⁶¹Hf , rowspan=2, 1/2+# , rowspan=2, , rowspan=2, , - , α (5%) , ¹⁵⁷Lu , - , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , 50(50)# keV , 2.89(12) s , , , 11/2−# , , , - , rowspan=2, , rowspan=2 style="text-align:right" , 73 , rowspan=2 style="text-align:right" , 89 , rowspan=2, 161.95729(6) , rowspan=2, 3.57(12) s , β⁺ (99.92%) , ¹⁶²Hf , rowspan=2, 3+# , rowspan=2, , rowspan=2, , - , α (.073%) , ¹⁵⁸Lu , - , rowspan=2, , rowspan=2 style="text-align:right" , 73 , rowspan=2 style="text-align:right" , 90 , rowspan=2, 162.95433(4) , rowspan=2, 10.6(18) s , β⁺ (99.8%) , ¹⁶³Hf , rowspan=2, 1/2+# , rowspan=2, , rowspan=2, , - , α (.2%) , ¹⁵⁹Lu , - , , style="text-align:right" , 73 , style="text-align:right" , 91 , 163.95353(3) , 14.2(3) s , β⁺ , ¹⁶⁴Hf , (3+) , , , - , , style="text-align:right" , 73 , style="text-align:right" , 92 , 164.950773(19) , 31.0(15) s , β⁺ , ¹⁶⁵Hf , 5/2−# , , , - , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , 60(30) keV , , , , 9/2−# , , , - , , style="text-align:right" , 73 , style="text-align:right" , 93 , 165.95051(3) , 34.4(5) s , β⁺ , ¹⁶⁶Hf , (2)+ , , , - , , style="text-align:right" , 73 , style="text-align:right" , 94 , 166.94809(3) , 1.33(7) min , β⁺ , ¹⁶⁷Hf , (3/2+) , , , - , , style="text-align:right" , 73 , style="text-align:right" , 95 , 167.94805(3) , 2.0(1) min , β⁺ , ¹⁶⁸Hf , (2−,3+) , , , - , , style="text-align:right" , 73 , style="text-align:right" , 96 , 168.94601(3) , 4.9(4) min , β⁺ , ¹⁶⁹Hf , (5/2+) , , , - , , style="text-align:right" , 73 , style="text-align:right" , 97 , 169.94618(3) , 6.76(6) min , β⁺ , ¹⁷⁰Hf , (3)(+#) , , , - , , style="text-align:right" , 73 , style="text-align:right" , 98 , 170.94448(3) , 23.3(3) min , β⁺ , ¹⁷¹Hf , (5/2−) , , , - , , style="text-align:right" , 73 , style="text-align:right" , 99 , 171.94490(3) , 36.8(3) min , β⁺ , ¹⁷²Hf , (3+) , , , - , , style="text-align:right" , 73 , style="text-align:right" , 100 , 172.94375(3) , 3.14(13) h , β⁺ , ¹⁷³Hf , 5/2− , , , - , , style="text-align:right" , 73 , style="text-align:right" , 101 , 173.94445(3) , 1.14(8) h , β⁺ , ''¹⁷⁴Hf'' , 3+ , , , - , , style="text-align:right" , 73 , style="text-align:right" , 102 , 174.94374(3) , 10.5(2) h , β⁺ , ¹⁷⁵Hf , 7/2+ , , , - , , style="text-align:right" , 73 , style="text-align:right" , 103 , 175.94486(3) , 8.09(5) h , β⁺ , ¹⁷⁶Hf , (1)− , , , - , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , 103.0(10) keV , 1.1(1) ms , IT , ¹⁷⁶Ta , (+) , , , - , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , 1372.6(11)+X keV , 3.8(4) µs , , , (14−) , , , - , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , 2820(50) keV , 0.97(7) ms , , , (20−) , , , - , , style="text-align:right" , 73 , style="text-align:right" , 104 , 176.944472(4) , 56.56(6) h , β⁺ , ¹⁷⁷Hf , 7/2+ , , , - , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , 73.36(15) keV , 410(7) ns , , , 9/2− , , , - , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , 186.15(6) keV , 3.62(10) µs , , , 5/2− , , , - , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , 1355.01(19) keV , 5.31(25) µs , , , 21/2− , , , - , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , 4656.3(5) keV , 133(4) µs , , , 49/2− , , , - , , style="text-align:right" , 73 , style="text-align:right" , 105 , 177.945778(16) , 9.31(3) min , β⁺ , ¹⁷⁸Hf , 1+ , , , - , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , 100(50)# keV , 2.36(8) h , β⁺ , ¹⁷⁸Hf , (7)− , , , - , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , 1570(50)# keV , 59(3) ms , , , (15−) , , , - , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , 3000(50)# keV , 290(12) ms , , , (21−) , , , - , , style="text-align:right" , 73 , style="text-align:right" , 106 , 178.9459295(23) , 1.82(3) y , EC , ¹⁷⁹Hf , 7/2+ , , , - , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , 30.7(1) keV , 1.42(8) µs , , , (9/2)− , , , - , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , 520.23(18) keV , 335(45) ns , , , (1/2)+ , , , - , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , 1252.61(23) keV , 322(16) ns , , , (21/2−) , , , - , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , 1317.3(4) keV , 9.0(2) ms , IT , ¹⁷⁹Ta , (25/2+) , , , - , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , 1327.9(4) keV , 1.6(4) µs , , , (23/2−) , , , - , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , 2639.3(5) keV , 54.1(17) ms , , , (37/2+) , , , - , rowspan=2, , rowspan=2 style="text-align:right" , 73 , rowspan=2 style="text-align:right" , 107 , rowspan=2, 179.9474648(24) , rowspan=2, 8.152(6) h , EC (86%) , ¹⁸⁰Hf , rowspan=2, 1+ , rowspan=2, , rowspan=2, , - , β⁻ (14%) , ''¹⁸⁰W'' , - , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , 77.1(8) keV , colspan=3 align=center,

Observationally stable Stable nuclides are nuclides that are not radioactive and so (unlike radionuclides) do not spontaneously undergo radioactive decay. When such nuclides are referred to in relation to specific elements, they are usually termed stable isotopes. Th ...

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 4.5×10¹⁶ yearsOne of the few (observationally) stable odd-odd nuclei , 9− , 1.2(2)×10⁻⁴ , , - , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , 1452.40(18) keV , 31.2(14) µs , , , 15− , , , - , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , 3679.0(11) keV , 2.0(5) µs , , , (22−) , , , - , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , 4171.0+X keV , 17(5) µs , , , (23, 24, 25) , , , - , , style="text-align:right" , 73 , style="text-align:right" , 108 , 180.9479958(20) , colspan=3 align=center, Observationally stableBelieved to undergo α decay to ¹⁷⁷Lu , 7/2+ , 0.99988(2) , , - , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , 6.238(20) keV , 6.05(12) µs , , , 9/2− , , , - , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , 615.21(3) keV , 18(1) µs , , , 1/2+ , , , - , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , 1485(3) keV , 25(2) µs , , , 21/2− , , , - , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , 2230(3) keV , 210(20) µs , , , 29/2− , , , - , , style="text-align:right" , 73 , style="text-align:right" , 109 , 181.9501518(19) , 114.43(3) d , β⁻ , ¹⁸²W , 3− , , , - , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , 16.263(3) keV , 283(3) ms , IT , ¹⁸²Ta , 5+ , , , - , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , 519.572(18) keV , 15.84(10) min , , , 10− , , , - , , style="text-align:right" , 73 , style="text-align:right" , 110 , 182.9513726(19) , 5.1(1) d , β⁻ , ¹⁸³W , 7/2+ , , , - , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , 73.174(12) keV , 107(11) ns , , , 9/2− , , , - , , style="text-align:right" , 73 , style="text-align:right" , 111 , 183.954008(28) , 8.7(1) h , β⁻ , ¹⁸⁴W , (5−) , , , - , , style="text-align:right" , 73 , style="text-align:right" , 112 , 184.955559(15) , 49.4(15) min , β⁻ , ¹⁸⁵W , (7/2+)# , , , - , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , 1308(29) keV , >1 ms , , , (21/2−) , , , - , , style="text-align:right" , 73 , style="text-align:right" , 113 , 185.95855(6) , 10.5(3) min , β⁻ , ¹⁸⁶W , (2−,3−) , , , - , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , , 1.54(5) min , , , , , , - , , style="text-align:right" , 73 , style="text-align:right" , 114 , 186.96053(21)# , 2# min
300 ns, β⁻ , ¹⁸⁷W , 7/2+# , , , - , , style="text-align:right" , 73 , style="text-align:right" , 115 , 187.96370(21)# , 20# s
300 ns, β⁻ , ¹⁸⁸W , , , , - , , style="text-align:right" , 73 , style="text-align:right" , 116 , 188.96583(32)# , 3# s
300 ns, , , 7/2+# , , , - , , style="text-align:right" , 73 , style="text-align:right" , 117 , 189.96923(43)# , 0.3# s , , , , ,

Tantalum-180m

The nuclide (''m'' denotes a metastable state) has sufficient energy to decay in three ways:

isomeric transition A nuclear isomer is a metastable state of an atomic nucleus, in which one or more nucleons (protons or neutrons) occupy higher energy levels than in the ground state of the same nucleus. "Metastable" describes nuclei whose excited states have ...

to the

ground state The ground state of a quantum-mechanical system is its stationary state of lowest energy; the energy of the ground state is known as the zero-point energy of the system. An excited state is any state with energy greater than the ground state. ...

of ,

beta decay In nuclear physics, beta decay (β-decay) is a type of radioactive decay in which a beta particle (fast energetic electron or positron) is emitted from an atomic nucleus, transforming the original nuclide to an isobar of that nuclide. For ...

to , and

electron capture Electron capture (K-electron capture, also K-capture, or L-electron capture, L-capture) is a process in which the proton-rich nucleus of an electrically neutral atom absorbs an inner atomic electron, usually from the K or L electron shells. ...

to . However, no radioactivity from any decay mode of this nuclear isomer has ever been observed. Only a lower limit on its

of over 10¹⁵ years has been set, by observation. 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. The very unusual nature of ^180mTa is that the ground state of this isotope is less stable than the isomer. This phenomenon is exhibited in

bismuth-210m Bismuth (83Bi) has 41 known isotopes, ranging from 184Bi to 224Bi. Bismuth has no stable isotopes, but does have one very long-lived isotope; thus, the standard atomic weight can be given as . Although bismuth-209 is now known to be unstable, it h ...

(^210mBi) and americium-242m (^242mAm), among other nuclides. has a half-life of only 8 hours. is the only naturally occurring nuclear isomer (excluding radiogenic and cosmogenic short-living nuclides). It is also the rarest

primordial nuclide In geochemistry, geophysics and nuclear physics, primordial nuclides, also known as primordial isotopes, are nuclides found on Earth that have existed in their current form since before Earth was formed. Primordial nuclides were present in the ...

in the Universe observed for any element that has any stable isotopes. In an

s-process The slow neutron-capture process, or ''s''-process, is a series of reactions in nuclear astrophysics that occur in stars, particularly asymptotic giant branch stars. The ''s''-process is responsible for the creation ( nucleosynthesis) of approxim ...

stellar environment with a thermal energy k_BT = 26 k eV (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. As of October 3, 2016 the half life of ^180mTa is calculated from experimental observation to be at least (45 quadrillion) years.

References

* Isotope masses from: ** * Isotopic compositions and standard atomic masses from: ** ** * Half-life, spin, and isomer data selected from the following sources. ** ** ** {{Navbox element isotopes Tantalum

Tantalum Tantalum is a chemical element with the symbol Ta and atomic number 73. Previously known as ''tantalium'', it is named after Tantalus, a villain in Greek mythology. Tantalum is a very hard, ductile, lustrous, blue-gray transition metal that ...