# Isotopes of molybdenum

Molybdenum ($_{42}$Mo) has 39 known isotopes, ranging in atomic mass from 81 to 119, as well as four metastable nuclear isomers. Seven isotopes occur naturally, with atomic masses of 92, 94, 95, 96, 97, 98, and 100. All unstable isotopes of molybdenum decay into isotopes of zirconium, niobium, technetium, and ruthenium.
Molybdenum-100, with a half-life of 7.07×10$^{18}$ years, is the only naturally occurring radioisotope. It undergoes double beta decay into ruthenium-100. Molybdenum-98 is the most common isotope, comprising 24.14% of all molybdenum on Earth.

## 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 |
| $^{81}$Mo | 42 | 39 | 80.96623(54)# | 1# ms [>400 ns] | β$^+$? | $^{81}$Nb | 5/2+# | | |
| $^{81}$Mo | 42 | 39 | 80.96623(54)# | 1# ms [>400 ns] | β$^+$, p? | $^{80}$Zr | 5/2+# | | |
| $^{82}$Mo | 42 | 40 | 81.95666(43)# | 30# ms [>400 ns] | β$^+$? | $^{82}$Nb | 0+ | | |
| $^{82}$Mo | 42 | 40 | 81.95666(43)# | 30# ms [>400 ns] | β$^+$, p? | $^{81}$Zr | 0+ | | |
| $^{83}$Mo | 42 | 41 | 82.95025(43)# | 23(19) ms | β$^+$ | $^{83}$Nb | 3/2−# | | |
| $^{83}$Mo | 42 | 41 | 82.95025(43)# | 23(19) ms | β$^+$, p? | $^{82}$Zr | 3/2−# | | |
| $^{84}$Mo | 42 | 42 | 83.94185(32)# | 2.3(3) s | β$^+$ | $^{84}$Nb | 0+ | | |
| $^{84}$Mo | 42 | 42 | 83.94185(32)# | 2.3(3) s | β$^+$, p? | $^{83}$Zr | 0+ | | |
| $^{85}$Mo | 42 | 43 | 84.938261(17) | 3.2(2) s | β$^+$ (99.86%) | $^{85}$Nb | (1/2+) | | |
| $^{85}$Mo | 42 | 43 | 84.938261(17) | 3.2(2) s | β$^+$, p (0.14%) | $^{84}$Zr | (1/2+) | | |
| $^{86}$Mo | 42 | 44 | 85.931174(3) | 19.1(3) s | β$^+$ | $^{86}$Nb | 0+ | | |
| $^{87}$Mo | 42 | 45 | 86.928196(3) | 14.1(3) s | β$^+$ (85%) | $^{87}$Nb | 7/2+# | | |
| $^{87}$Mo | 42 | 45 | 86.928196(3) | 14.1(3) s | β$^+$, p (15%) | $^{86}$Zr | 7/2+# | | |
| $^{88}$Mo | 42 | 46 | 87.921968(4) | 8.0(2) min | β$^+$ | $^{88}$Nb | 0+ | | |
| $^{89}$Mo | 42 | 47 | 88.919468(4) | 2.11(10) min | β$^+$ | $^{89}$Nb | (9/2+) | | |
| $^{89m}$Mo | 387.5(2) keV | 387.5(2) keV | 387.5(2) keV | 190(15) ms | IT | $^{89}$Mo | (1/2−) | | |
| $^{90}$Mo | 42 | 48 | 89.913931(4) | 5.56(9) h | β$^+$ | $^{90}$Nb | 0+ | | |
| $^{90m}$Mo | 2874.73(15) keV | 2874.73(15) keV | 2874.73(15) keV | 1.14(5) μs | IT | $^{90}$Mo | 8+ | | |
| $^{91}$Mo | 42 | 49 | 90.911745(7) | 15.49(1) min | β$^+$ | $^{91}$Nb | 9/2+ | | |
| $^{91m}$Mo | 653.01(9) keV | 653.01(9) keV | 653.01(9) keV | 64.6(6) s | IT (50.0%) | $^{91}$Mo | 1/2− | | |
| $^{91m}$Mo | 653.01(9) keV | 653.01(9) keV | 653.01(9) keV | 64.6(6) s | β$^+$ (50.0%) | $^{91}$Nb | 1/2− | | |
| $^{92}$Mo | 42 | 50 | 91.90680715(17) | Observationally Stable | Observationally Stable | Observationally Stable | 0+ | 0.14649(106) | |
| $^{92m}$Mo | 2760.52(14) keV | 2760.52(14) keV | 2760.52(14) keV | 190(3) ns | IT | $^{92}$Mo | 8+ | | |
| $^{93}$Mo | 42 | 51 | 92.90680877(19) | 4839(63) y | EC (95.7%) | $^{93m}$Nb | 5/2+ | | |
| $^{93}$Mo | 42 | 51 | 92.90680877(19) | 4839(63) y | EC (4.3%) | $^{93}$Nb | 5/2+ | | |
| $^{93m1}$Mo | 2424.95(4) keV | 2424.95(4) keV | 2424.95(4) keV | 6.85(7) h | IT (99.88%) | $^{93}$Mo | 21/2+ | | |
| $^{93m1}$Mo | 2424.95(4) keV | 2424.95(4) keV | 2424.95(4) keV | 6.85(7) h | β$^+$ (0.12%) | $^{93}$Nb | 21/2+ | | |
| $^{93m2}$Mo | 9695(17) keV | 9695(17) keV | 9695(17) keV | 1.8(10) μs | IT | $^{93}$Mo | (39/2−) | | |
| $^{94}$Mo | 42 | 52 | 93.90508359(15) | Stable | Stable | Stable | 0+ | 0.09187(33) | |
| $^{95}$Mo | 42 | 53 | 94.90583744(13) | Stable | Stable | Stable | 5/2+ | 0.15873(30) | |
| $^{96}$Mo | 42 | 54 | 95.90467477(13) | Stable | Stable | Stable | 0+ | 0.16673(8) | |
| $^{97}$Mo | 42 | 55 | 96.90601690(18) | Stable | Stable | Stable | 5/2+ | 0.09582(15) | |
| $^{98}$Mo | 42 | 56 | 97.90540361(19) | Observationally Stable | Observationally Stable | Observationally Stable | 0+ | 0.24292(80) | |
| $^{99}$Mo | 42 | 57 | 98.90770730(25) | 65.932(5) h | β$^−$ | $^{99m}$Tc | 1/2+ | | |
| $^{99m1}$Mo | 97.785(3) keV | 97.785(3) keV | 97.785(3) keV | 15.5(2) μs | IT | $^{99}$Mo | 5/2+ | | |
| $^{99m2}$Mo | 684.10(19) keV | 684.10(19) keV | 684.10(19) keV | 760(60) ns | IT | $^{99}$Mo | 11/2− | | |
| $^{100}$Mo | 42 | 58 | 99.9074680(3) | 7.07(14)×10$^{18}$ y | β$^−$β$^−$ | $^{100}$Ru | 0+ | 0.09744(65) | |
| $^{101}$Mo | 42 | 59 | 100.9103376(3) | 14.61(3) min | β$^−$ | $^{101}$Tc | 1/2+ | | |
| $^{101m1}$Mo | 13.497(9) keV | 13.497(9) keV | 13.497(9) keV | 226(7) ns | IT | $^{101}$Mo | 3/2+ | | |
| $^{101m2}$Mo | 57.015(11) keV | 57.015(11) keV | 57.015(11) keV | 133(70) ns | IT | $^{101}$Mo | 5/2+ | | |
| $^{102}$Mo | 42 | 60 | 101.910294(9) | 11.3(2) min | β$^−$ | $^{102}$Tc | 0+ | | |
| $^{103}$Mo | 42 | 61 | 102.913092(10) | 67.5(15) s | β$^−$ | $^{103}$Tc | 3/2+ | | |
| $^{104}$Mo | 42 | 62 | 103.913747(10) | 60(2) s | β$^−$ | $^{104}$Tc | 0+ | | |
| $^{105}$Mo | 42 | 63 | 104.9169798(23) | 36.3(8) s | β$^−$ | $^{105}$Tc | (5/2−) | | |
| $^{106}$Mo | 42 | 64 | 105.9182732(98) | 8.73(12) s | β$^−$ | $^{106}$Tc | 0+ | | |
| $^{107}$Mo | 42 | 65 | 106.9221198(99) | 3.5(5) s | β$^−$ | $^{107}$Tc | (1/2+) | | |
| $^{107m}$Mo | 65.4(2) keV | 65.4(2) keV | 65.4(2) keV | 445(21) ns | IT | $^{107}$Mo | (5/2+) | | |
| $^{108}$Mo | 42 | 66 | 107.9240475(99) | 1.105(10) s | β$^−$ (>99.5%) | $^{108}$Tc | 0+ | | |
| $^{108}$Mo | 42 | 66 | 107.9240475(99) | 1.105(10) s | β$^−$, n (<0.5%) | $^{107}$Tc | 0+ | | |
| $^{109}$Mo | 42 | 67 | 108.928438(12) | 700(14) ms | β$^−$ (98.7%) | $^{109}$Tc | (1/2+) | | |
| $^{109}$Mo | 42 | 67 | 108.928438(12) | 700(14) ms | β$^−$, n (1.3%) | $^{108}$Tc | (1/2+) | | |
| $^{109m}$Mo | 69.7(5) keV | 69.7(5) keV | 69.7(5) keV | 210(60) ns | IT | $^{109}$Mo | 5/2+# | | |
| $^{110}$Mo | 42 | 68 | 109.930718(26) | 292(7) ms | β$^−$ (98.0%) | $^{110}$Tc | 0+ | | |
| $^{110}$Mo | 42 | 68 | 109.930718(26) | 292(7) ms | β$^−$, n (2.0%) | $^{109}$Tc | 0+ | | |
| $^{111}$Mo | 42 | 69 | 110.935652(14) | 193.6(44) ms | β$^−$ (>88%) | $^{111}$Tc | 1/2+# | | |
| $^{111}$Mo | 42 | 69 | 110.935652(14) | 193.6(44) ms | β$^−$, n (<12%) | $^{110}$Tc | 1/2+# | | |
| $^{111m}$Mo | 100(50)# keV | 100(50)# keV | 100(50)# keV | ~200 ms | β$^−$ | $^{111}$Tc | 7/2−# | | |
| $^{111m}$Mo | 100(50)# keV | 100(50)# keV | 100(50)# keV | ~200 ms | β$^−$, n? | $^{110}$Tc | 7/2−# | | |
| $^{112}$Mo | 42 | 70 | 111.93829(22)# | 125(5) ms | β$^−$ | $^{112}$Tc | 0+ | | |
| $^{112}$Mo | 42 | 70 | 111.93829(22)# | 125(5) ms | β$^−$, n? | $^{111}$Tc | 0+ | | |
| $^{113}$Mo | 42 | 71 | 112.94348(32)# | 80(2) ms | β$^−$ | $^{113}$Tc | 5/2+# | | |
| $^{113}$Mo | 42 | 71 | 112.94348(32)# | 80(2) ms | β$^−$, n? | $^{112}$Tc | 5/2+# | | |
| $^{114}$Mo | 42 | 72 | 113.94667(32)# | 58(2) ms | β$^−$ | $^{114}$Tc | 0+ | | |
| $^{114}$Mo | 42 | 72 | 113.94667(32)# | 58(2) ms | β$^−$, n? | $^{113}$Tc | 0+ | | |
| $^{115}$Mo | 42 | 73 | 114.95217(43)# | 45.5(20) ms | β$^−$ | $^{115}$Tc | 3/2+# | | |
| $^{115}$Mo | 42 | 73 | 114.95217(43)# | 45.5(20) ms | β$^−$, n? | $^{114}$Tc | 3/2+# | | |
| $^{115}$Mo | 42 | 73 | 114.95217(43)# | 45.5(20) ms | β$^−$, 2n? | $^{113}$Tc | 3/2+# | | |
| $^{116}$Mo | 42 | 74 | 115.95576(54)# | 32(4) ms | β$^−$ | $^{116}$Tc | 0+ | | |
| $^{116}$Mo | 42 | 74 | 115.95576(54)# | 32(4) ms | β$^−$, n? | $^{115}$Tc | 0+ | | |
| $^{116}$Mo | 42 | 74 | 115.95576(54)# | 32(4) ms | β$^−$, 2n? | $^{114}$Tc | 0+ | | |
| $^{117}$Mo | 42 | 75 | 116.96169(54)# | 22(5) ms | β$^−$ | $^{117}$Tc | 3/2+# | | |
| $^{117}$Mo | 42 | 75 | 116.96169(54)# | 22(5) ms | β$^−$, n? | $^{116}$Tc | 3/2+# | | |
| $^{117}$Mo | 42 | 75 | 116.96169(54)# | 22(5) ms | β$^−$, 2n? | $^{115}$Tc | 3/2+# | | |
| $^{118}$Mo | 42 | 76 | 117.96525(54)# | 21(6) ms | β$^−$ | $^{118}$Tc | 0+ | | |
| $^{118}$Mo | 42 | 76 | 117.96525(54)# | 21(6) ms | β$^−$, n? | $^{117}$Tc | 0+ | | |
| $^{118}$Mo | 42 | 76 | 117.96525(54)# | 21(6) ms | β$^−$, 2n? | $^{116}$Tc | 0+ | | |
| $^{119}$Mo | 42 | 77 | 118.97147(32)# | 12# ms [>550 ns] | β$^−$? | $^{119}$Tc | 3/2+# | | |
| $^{119}$Mo | 42 | 77 | 118.97147(32)# | 12# ms [>550 ns] | β$^−$, n? | $^{118}$Tc | 3/2+# | | |
| $^{119}$Mo | 42 | 77 | 118.97147(32)# | 12# ms [>550 ns] | β$^−$, 2n? | $^{117}$Tc | 3/2+# | | |
| This table header & footer: view ||||||||||
* ↑ $^m$Mb – 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.
* ↑ 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.
* ↑ # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
* ↑ Believed to decay by β$^+$β$^+$ to $^{92}$Zr with a half-life over 1.9×10$^{20}$ y
* 1 2 3 4 5 Fission product
* ↑ Believed to decay by β$^−$β$^−$ to $^{98}$Ru with a half-life of over 1×10$^{14}$ years
* ↑ Used to produce the medically useful radioisotope technetium-99m
* ↑ Primordial radionuclide

## Molybdenum-99

Molybdenum-99 is produced commercially by intense neutron-bombardment of a highly purified uranium-235 target, followed rapidly by extraction. It is used as a parent radioisotope in technetium-99m generators to produce the even shorter-lived daughter isotope technetium-99m, which is used in approximately 40 million medical procedures annually. A common misunderstanding or misnomer is that $^{99}$Mo is used in these diagnostic medical scans, when actually it has no role in the imaging agent or the scan itself. In fact, $^{99}$Mo co-eluted with the $^{99m}$Tc (also known as breakthrough) is considered a contaminant and is minimised to adhere to the appropriate USP (or equivalent) regulations and standards. The IAEA recommends that $^{99}$Mo concentrations exceeding more than 0.15 μCi/mCi $^{99m}$Tc or 0.015% should not be administered for usage in humans. Typically, quantification of $^{99}$Mo breakthrough is performed for every elution when using a $^{99}$Mo/$^{99m}$Tc generator during QA-QC testing of the final product.
There are alternative routes for generating $^{99}$Mo that do not require a fissionable target, such as high or low enriched uranium (i.e., HEU or LEU). Some of these include accelerator-based methods, such as proton bombardment or photoneutron reactions on enriched $^{100}$Mo targets. Historically, $^{99}$Mo generated by neutron capture on natural isotopic molybdenum or enriched $^{98}$Mo targets was used for the development of commercial $^{99}$Mo/$^{99m}$Tc generators. The neutron-capture process was eventually superseded by fission-based $^{99}$Mo that could be generated with much higher specific activities. Implementing feed-stocks of high specific activity $^{99}$Mo solutions thus allowed for higher quality production and better separations of $^{99m}$Tc from $^{99}$Mo on small alumina column using chromatography. Employing low-specific activity $^{99}$Mo under similar conditions is particularly problematic in that either higher Mo loading capacities or larger columns are required for accommodating equivalent amounts of $^{99}$Mo. Chemically speaking, this phenomenon occurs due to other Mo isotopes present aside from $^{99}$Mo that compete for surface site interactions on the column substrate. In turn, low-specific activity $^{99}$Mo usually requires much larger column sizes and longer separation times, and usually yields $^{99m}$Tc accompanied by unsatisfactory amounts of the parent radioisotope when using γ-alumina as the column substrate. Ultimately, the inferior end-product $^{99m}$Tc generated under these conditions makes it essentially incompatible with the commercial supply-chain.
In the last decade, cooperative agreements between the US government and private capital entities have resurrected neutron capture production for commercially distributed $^{99}$Mo/$^{99m}$Tc in the United States of America. The return to neutron-capture-based $^{99}$Mo has also been accompanied by the implementation of novel separation methods that allow for low-specific activity $^{99}$Mo to be utilized.