# Isotopes of tellurium

There are 39 known isotopes and 17 nuclear isomers of tellurium ($_{52}$Te), with atomic masses that range from 104 to 142. These are listed in the table below.
Naturally-occurring tellurium on Earth consists of eight isotopes. Two of these have been found to be radioactive: $^{128}$Te and $^{130}$Te undergo double beta decay with half-lives of, respectively, 2.2×10$^{24}$ (2.2 septillion) years (the longest half-life of all nuclides proven to be radioactive) and 8.2×10$^{20}$ (820 quintillion) years. The longest-lived artificial radioisotope of tellurium is $^{121}$Te with a half-life of about 19 days. Several nuclear isomers have longer half-lives, the longest being $^{121m}$Te with a half-life of 154 days.
The very-long-lived radioisotopes $^{128}$Te and $^{130}$Te are the two most common isotopes of tellurium. Of elements with at least one stable isotope, only indium and rhenium likewise have a radioisotope in greater abundance than a stable one.
It has been claimed that electron capture of $^{123}$Te was observed, but more recent measurements of the same team have disproved this. The half-life of $^{123}$Te is longer than 9.2 × 10$^{16}$ years, and probably much longer.
$^{124}$Te can be used as a starting material in the production of radionuclides by a cyclotron or other particle accelerators. Some common radionuclides that can be produced from tellurium-124 are iodine-123 and iodine-124.
The short-lived isotope $^{135}$Te (half-life 19 seconds) is produced as a fission product in nuclear reactors. It decays, via two beta decays, to $^{135}$Xe, the most powerful known neutron absorber, and the cause of the iodine pit phenomenon.
With the exception of beryllium, tellurium is the second lightest element observed to have isotopes capable of undergoing alpha decay, with isotopes $^{104}$Te to $^{109}$Te being seen to undergo this mode of decay. Some lighter elements, namely those in the vicinity of $^8$Be, have isotopes with delayed alpha emission (following proton or beta emission) as a rare branch.

## List of isotopes

| Nuclide | Z | N | Isotopic mass (Da) | Half-life | Decay mode | Daughter isotope | Spin and parity | Natural abundance (mole fraction) | Natural abundance (mole fraction) |
| Nuclide | Excitation energy | Excitation energy | Excitation energy | Half-life | Decay mode | Daughter isotope | Spin and parity | Normal proportion | Range of variation |
| $^{104}$Te | 52 | 52 | 103.94672(34) | <4 ns | α | $^{100}$Sn | 0+ | | |
| $^{105}$Te | 52 | 53 | 104.94330(32) | 633(66) ns | α | $^{101}$Sn | (7/2+) | | |
| $^{106}$Te | 52 | 54 | 105.93750(11) | 78(11) μs | α | $^{102}$Sn | 0+ | | |
| $^{107}$Te | 52 | 55 | 106.93488(11)# | 3.22(9) ms | α (70%) | $^{103}$Sn | 5/2+# | | |
| $^{107}$Te | 52 | 55 | 106.93488(11)# | 3.22(9) ms | β$^+$ (30%) | $^{107}$Sb | 5/2+# | | |
| $^{108}$Te | 52 | 56 | 107.9293805(58) | 2.1(1) s | α (49%) | $^{104}$Sn | 0+ | | |
| $^{108}$Te | 52 | 56 | 107.9293805(58) | 2.1(1) s | β$^+$ (48.6%) | $^{108}$Sb | 0+ | | |
| $^{108}$Te | 52 | 56 | 107.9293805(58) | 2.1(1) s | β$^+$, p (2.4%) | $^{107}$Sn | 0+ | | |
| $^{108}$Te | 52 | 56 | 107.9293805(58) | 2.1(1) s | β$^+$, α (<0.065%) | $^{104}$In | 0+ | | |
| $^{109}$Te | 52 | 57 | 108.9273045(47) | 4.4(2) s | β$^+$ (86.7%) | $^{109}$Sb | (5/2+) | | |
| $^{109}$Te | 52 | 57 | 108.9273045(47) | 4.4(2) s | β$^+$, p (9.4%) | $^{108}$Sn | (5/2+) | | |
| $^{109}$Te | 52 | 57 | 108.9273045(47) | 4.4(2) s | α (3.9%) | $^{105}$Sn | (5/2+) | | |
| $^{109}$Te | 52 | 57 | 108.9273045(47) | 4.4(2) s | β$^+$, α (<0.0049%) | $^{105}$In | (5/2+) | | |
| $^{110}$Te | 52 | 58 | 109.9224581(71) | 18.6(8) s | β$^+$ | $^{110}$Sb | 0+ | | |
| $^{111}$Te | 52 | 59 | 110.9210006(69) | 26.2(6) s | β$^+$ | $^{111}$Sb | (5/2)+ | | |
| $^{111}$Te | 52 | 59 | 110.9210006(69) | 26.2(6) s | β$^+$, p (?%) | $^{110}$Sn | (5/2)+ | | |
| $^{112}$Te | 52 | 60 | 111.9167278(90) | 2.0(2) min | β$^+$ | $^{112}$Sb | 0+ | | |
| $^{113}$Te | 52 | 61 | 112.915891(30) | 1.7(2) min | β$^+$ | $^{113}$Sb | (7/2+) | | |
| $^{114}$Te | 52 | 62 | 113.912088(26) | 15.2(7) min | β$^+$ | $^{114}$Sb | 0+ | | |
| $^{115}$Te | 52 | 63 | 114.911902(30) | 5.8(2) min | β$^+$ | $^{115}$Sb | 7/2+ | | |
| $^{115m1}$Te | 10(6) keV | 10(6) keV | 10(6) keV | 6.7(4) min | β$^+$ | $^{115}$Sb | (1/2+) | | |
| $^{115m2}$Te | 280.05(20) keV | 280.05(20) keV | 280.05(20) keV | 7.5(2) μs | IT | $^{115}$Te | 11/2− | | |
| $^{116}$Te | 52 | 64 | 115.908466(26) | 2.49(4) h | β$^+$ | $^{116}$Sb | 0+ | | |
| $^{117}$Te | 52 | 65 | 116.908646(14) | 62(2) min | EC (75%) | $^{117}$Sb | 1/2+ | | |
| $^{117}$Te | 52 | 65 | 116.908646(14) | 62(2) min | β$^+$ | $^{117}$Sb | 1/2+ | | |
| $^{117m}$Te | 296.1(5) keV | 296.1(5) keV | 296.1(5) keV | 103(3) ms | IT | $^{117}$Te | (11/2−) | |
| $^{118}$Te | 52 | 66 | 117.905860(20) | 6.00(2) d | EC | $^{118}$Sb | 0+ | | |
| $^{119}$Te | 52 | 67 | 118.9064057(78) | 16.05(5) h | EC (97.94%) | $^{119}$Sb | 1/2+ | | |
| $^{119}$Te | 52 | 67 | 118.9064057(78) | 16.05(5) h | β$^+$ (2.06%) | $^{119}$Sb | 1/2+ | | |
| $^{119m}$Te | 260.96(5) keV | 260.96(5) keV | 260.96(5) keV | 4.70(4) d | EC (99.59%) | $^{119}$Sb | 11/2− | | |
| $^{119m}$Te | 260.96(5) keV | 260.96(5) keV | 260.96(5) keV | 4.70(4) d | β$^+$ (0.41%) | $^{119}$Sb | 11/2− | | |
| $^{120}$Te | 52 | 68 | 119.9040658(19) | Observationally Stable | Observationally Stable | Observationally Stable | 0+ | 9(1)×10$^{−4}$ | |
| $^{121}$Te | 52 | 69 | 120.904945(28) | 19.31(7) d | β$^+$ | $^{121}$Sb | 1/2+ | | |
| $^{121m}$Te | 293.974(22) keV | 293.974(22) keV | 293.974(22) keV | 164.7(5) d | IT (88.6%) | $^{121}$Te | 11/2− | | |
| $^{121m}$Te | 293.974(22) keV | 293.974(22) keV | 293.974(22) keV | 164.7(5) d | β$^+$ (11.4%) | $^{121}$Sb | 11/2− | | |
| $^{122}$Te | 52 | 70 | 121.9030447(15) | Stable | Stable | Stable | 0+ | 0.0255(12) | |
| $^{123}$Te | 52 | 71 | 122.9042710(15) | Observationally Stable | Observationally Stable | Observationally Stable | 1/2+ | 0.0089(3) | |
| $^{123m}$Te | 247.47(4) keV | 247.47(4) keV | 247.47(4) keV | 119.2(1) d | IT | $^{123}$Te | 11/2− | | |
| $^{124}$Te | 52 | 72 | 123.9028183(15) | Stable | Stable | Stable | 0+ | 0.0474(14) | |
| $^{125}$Te | 52 | 73 | 124.9044312(15) | Stable | Stable | Stable | 1/2+ | 0.0707(15) | |
| $^{125m}$Te | 144.775(8) keV | 144.775(8) keV | 144.775(8) keV | 57.40(15) d | IT | $^{125}$Te | 11/2− | | |
| $^{126}$Te | 52 | 74 | 125.9033121(15) | Stable | Stable | Stable | 0+ | 0.1884(25) | |
| $^{127}$Te | 52 | 75 | 126.9052270(15) | 9.35(7) h | β$^−$ | $^{127}$I | 3/2+ | | |
| $^{127m}$Te | 88.23(7) keV | 88.23(7) keV | 88.23(7) keV | 106.1(7) d | IT (97.86%) | $^{127}$Te | 11/2− | | |
| $^{127m}$Te | 88.23(7) keV | 88.23(7) keV | 88.23(7) keV | 106.1(7) d | β$^−$ (2.14%) | $^{127}$I | 11/2− | | |
| $^{128}$Te | 52 | 76 | 127.90446124(76) | 2.25(9)×10$^{24}$ y | β$^−$β$^−$ | $^{128}$Xe | 0+ | 0.3174(8) | |
| $^{128m}$Te | 2790.8(3) keV | 2790.8(3) keV | 2790.8(3) keV | 363(27) ns | IT | $^{128}$Te | (10+) | | |
| $^{129}$Te | 52 | 77 | 128.90659642(76) | 69.6(3) min | β$^−$ | $^{129}$I | 3/2+ | | |
| $^{129m}$Te | 105.51(3) keV | 105.51(3) keV | 105.51(3) keV | 33.6(1) d | IT (64%) | $^{129}$Te | 11/2− | | |
| $^{129m}$Te | 105.51(3) keV | 105.51(3) keV | 105.51(3) keV | 33.6(1) d | β$^−$ (36%) | $^{129}$I | 11/2− | | |
| $^{130}$Te | 52 | 78 | 129.906222745(11) | 7.91(21)×10$^{20}$ y | β$^−$β$^−$ | $^{130}$Xe | 0+ | 0.3408(62) | |
| $^{130m1}$Te | 2146.41(4) keV | 2146.41(4) keV | 2146.41(4) keV | 186(11) ns | IT | $^{130}$Te | 7− | | |
| $^{130m2}$Te | 2667.2(8) keV | 2667.2(8) keV | 2667.2(8) keV | 1.90(8) μs | IT | $^{130}$Te | (10+) | | |
| $^{130m3}$Te | 4373.9(9) keV | 4373.9(9) keV | 4373.9(9) keV | 53(8) ns | IT | $^{130}$Te | (15−) | | |
| $^{131}$Te | 52 | 79 | 130.908522210(65) | 25.0(1) min | β$^−$ | $^{131}$I | 3/2+ | | |
| $^{131m1}$Te | 182.258(18) keV | 182.258(18) keV | 182.258(18) keV | 32.48(11) h | β$^−$ (74.1%) | $^{131}$I | 11/2− | | |
| $^{131m1}$Te | 182.258(18) keV | 182.258(18) keV | 182.258(18) keV | 32.48(11) h | IT (25.9%) | $^{131}$Te | 11/2− | | |
| $^{131m2}$Te | 1940.0(4) keV | 1940.0(4) keV | 1940.0(4) keV | 93(12) ms | IT | $^{131}$Te | (23/2+) | | |
| $^{132}$Te | 52 | 80 | 131.9085467(37) | 3.204(13) d | β$^−$ | $^{132}$I | 0+ | | |
| $^{132m1}$Te | 1774.80(9) keV | 1774.80(9) keV | 1774.80(9) keV | 145(8) ns | IT | $^{132}$Te | 6+ | | |
| $^{132m2}$Te | 1925.47(9) keV | 1925.47(9) keV | 1925.47(9) keV | 28.5(9) μs | IT | $^{132}$Te | 7− | | |
| $^{132m3}$Te | 2723.3(8) keV | 2723.3(8) keV | 2723.3(8) keV | 3.62(6) μs | IT | $^{132}$Te | (10+) | | |
| $^{133}$Te | 52 | 81 | 132.9109633(22) | 12.5(3) min | β$^−$ | $^{133}$I | 3/2+# | | |
| $^{133m1}$Te | 334.26(4) keV | 334.26(4) keV | 334.26(4) keV | 55.4(4) min | β$^−$ (83.5%) | $^{133}$I | (11/2−) | | |
| $^{133m1}$Te | 334.26(4) keV | 334.26(4) keV | 334.26(4) keV | 55.4(4) min | IT (16.5%) | $^{133}$Te | (11/2−) | | |
| $^{133m2}$Te | 1610.4(5) keV | 1610.4(5) keV | 1610.4(5) keV | 100(5) ns | IT | $^{133}$Te | (19/2−) | | |
| $^{134}$Te | 52 | 82 | 133.9113964(29) | 41.8(8) min | β$^−$ | $^{134}$I | 0+ | | |
| $^{134m}$Te | 1691.34(16) keV | 1691.34(16) keV | 1691.34(16) keV | 164.5(7) ns | IT | $^{134}$Te | 6+ | | |
| $^{135}$Te | 52 | 83 | 134.9165547(18) | 19.0(2) s | β$^−$ | $^{135}$I | (7/2−) | | |
| $^{135m}$Te | 1554.89(16) keV | 1554.89(16) keV | 1554.89(16) keV | 511(20) ns | IT | $^{135}$Te | (19/2−) | | |
| $^{136}$Te | 52 | 84 | 135.9201012(24) | 17.63(9) s | β$^−$ (98.63%) | $^{136}$I | 0+ | | |
| $^{136}$Te | 52 | 84 | 135.9201012(24) | 17.63(9) s | β$^−$, n (1.37%) | $^{135}$I | 0+ | | |
| $^{137}$Te | 52 | 85 | 136.9255994(23) | 2.49(5) s | β$^−$ (97.06%) | $^{137}$I | 3/2−# | | |
| $^{137}$Te | 52 | 85 | 136.9255994(23) | 2.49(5) s | β$^−$, n (2.94%) | $^{136}$I | 3/2−# | | |
| $^{138}$Te | 52 | 86 | 137.9294725(41) | 1.46(25) s | β$^−$ (95.20%) | $^{138}$I | 0+ | | |
| $^{138}$Te | 52 | 86 | 137.9294725(41) | 1.46(25) s | β$^−$, n (4.80%) | $^{137}$I | 0+ | | |
| $^{139}$Te | 52 | 87 | 138.9353672(38) | 724(81) ms | β$^−$ | $^{139}$I | 5/2−# | | |
| $^{140}$Te | 52 | 88 | 139.939487(15) | 351(5) ms | β$^−$ (?%) | $^{140}$I | 0+ | | |
| $^{140}$Te | 52 | 88 | 139.939487(15) | 351(5) ms | β$^−$, n (?%) | $^{139}$I | 0+ | | |
| $^{141}$Te | 52 | 89 | 140.94560(43)# | 193(16) ms | β$^−$ | $^{141}$I | 5/2−# | | |
| $^{142}$Te | 52 | 90 | 141.95003(54)# | 147(8) ms | β$^−$ | $^{142}$I | 0+ | | |
| $^{143}$Te | 52 | 91 | 142.95649(54)# | 120(8) ms | β$^−$ | $^{143}$I | 7/2+# | | |
| $^{144}$Te | 52 | 92 | 143.96112(32)# | 93(60) ms | β$^−$ | $^{144}$I | 0+ | | |
| $^{145}$Te | 52 | 93 | 144.96778(32)# | 75# ms [>550 ns] | β$^−$ | $^{145}$I | | | |
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* ↑ $^m$Te – Excited nuclear isomer.
* ↑ ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
* ↑ # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
* ↑ Bold half-life – nearly stable, half-life longer than age of universe.
* 1 2 # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
* ↑ Modes of decay: EC:Electron capture IT:Isomeric transition n:Neutron emission p:Proton emission
* ↑ Bold symbol as daughter – Daughter product is stable.
* ↑ ( ) spin value – Indicates spin with weak assignment arguments.
* ↑ Order of ground state and isomer is uncertain.
* ↑ Believed to undergo β$^+$β$^+$ decay to $^{120}$Sn with a half-life over 1.6×10$^{21}$ years
* ↑ Believed to undergo electron capture to $^{123}$Sb with a half-life over 9.2×10$^{16}$ years
* 1 2 3 4 5 6 7 Fission product
* 1 2 Primordial radionuclide
* ↑ Longest measured half-life of any nuclide
* ↑ Very short-lived fission product, responsible for the iodine pit as precursor of $^{135}$Xe via $^{135}$I