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 is ...
(
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 numbers) ...
s:
181Ta (99.988%) and (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. 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 ha ...
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 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 bom ...
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, pr ...
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 ato ...
of 114.43 days and produce approximately 1.12
MeV
In physics, an electronvolt (symbol eV, also written electron-volt and electron volt) is the measure of an amount of kinetic energy gained by a single electron accelerating from rest through an Voltage, electric potential difference of one volt i ...
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 harmf ...
(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
, -
,
, 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[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 years][One of the few (observationally) stable ]odd-odd nuclei
In nuclear physics, properties of a nucleus depend on evenness or oddness of its atomic number (proton number) ''Z'', neutron number ''N'' and, consequently, of their sum, the mass number ''A''. Most importantly, oddness of both ''Z'' and ''N'' ...
, 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 stable
[Believed 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 ha ...
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. Thi ...
to
. However, no radioactivity from any decay mode of this
nuclear isomer has ever been observed. Only a lower limit on its
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 ato ...
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 (
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 approximat ...
stellar environment with a thermal energy
kBT = 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:
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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.
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{{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 is ...