Isotopes of molybdenum

Molybdenum (₄₂Mo) has seven isotopes in nature, with atomic masses of 92, 94-98, and 100. All are stable except ¹⁰⁰Mo, which undergoes double beta decay with a half-life of 7.07 years (the shortest known for this mode) to ¹⁰⁰Ru. ⁹²Mo and ⁹⁸Mo are also energetically able to decay in this manner, to zirconium and ruthenium respectively; the others are theoretically stable. There are also a total of 32 synthetic isotopes known, and at least 13 metastable nuclear isomers, ranging in atomic mass from 81 to 119.

The isotopes with mass 93 or lower decay by electron capture or positron emission to niobium isotopes (or zirconium after delayed proton emission); those with mass 99 or higher by ordinary beta decay to technetium. The most stable of the former are ⁹³Mo, recently measured to have a half-life around 4800 years, and ⁹⁰Mo at 5.56 hours. The most stable of the latter is the medically important ⁹⁹Mo, half-life 65.932 hours, and whose decay leads to the chief isotope of technetium. By far the most stable isomer is ^93m1Mo at 6.85 hours, decaying to its ground state.

List of isotopes

|-id=Molybdenum-81 | rowspan=2|⁸¹Mo | rowspan=2 style="text-align:right" | 42 | rowspan=2 style="text-align:right" | 39 | rowspan=2|80.96623(54)# | rowspan=2|1#&nbsp;ms<br>[>400&nbsp;ns] | β⁺? | ⁸¹Nb | rowspan=2|5/2+# | rowspan=2| | rowspan=2| |- | β⁺, p? | ⁸⁰Zr |-id=Molybdenum-82 | rowspan=2|⁸²Mo | rowspan=2 style="text-align:right" | 42 | rowspan=2 style="text-align:right" | 40 | rowspan=2|81.95666(43)# | rowspan=2|30#&nbsp;ms<br>[>400&nbsp;ns] | β⁺? | ⁸²Nb | rowspan=2|0+ | rowspan=2| | rowspan=2| |- | β⁺, p? | ⁸¹Zr |-id=Molybdenum-83 | rowspan=2|⁸³Mo | rowspan=2 style="text-align:right" | 42 | rowspan=2 style="text-align:right" | 41 | rowspan=2|82.95025(43)# | rowspan=2|23(19)&nbsp;ms | β⁺ | ⁸³Nb | rowspan=2|3/2−# | rowspan=2| | rowspan=2| |- | β⁺, p? | ⁸²Zr |-id=Molybdenum-84 | rowspan=2|⁸⁴Mo | rowspan=2 style="text-align:right" | 42 | rowspan=2 style="text-align:right" | 42 | rowspan=2|83.941882(24) | rowspan=2|2.3(3)&nbsp;s | β⁺ | ⁸⁴Nb | rowspan=2|0+ | rowspan=2| | rowspan=2| |- | β⁺, p? | ⁸³Zr |-id=Molybdenum-85 | rowspan=2|⁸⁵Mo | rowspan=2 style="text-align:right" | 42 | rowspan=2 style="text-align:right" | 43 | rowspan=2|84.938261(17) | rowspan=2|3.2(2)&nbsp;s | β⁺ (99.86%) | ⁸⁵Nb | rowspan=2|(1/2+) | rowspan=2| | rowspan=2| |- | β⁺, p (0.14%) | ⁸⁴Zr |-id=Molybdenum-86 | ⁸⁶Mo | style="text-align:right" | 42 | style="text-align:right" | 44 | 85.931174(3) | 19.1(3)&nbsp;s | β⁺ | ⁸⁶Nb | 0+ | | |-id=Molybdenum-87 | rowspan=2|⁸⁷Mo | rowspan=2 style="text-align:right" | 42 | rowspan=2 style="text-align:right" | 45 | rowspan=2|86.928196(3) | rowspan=2|14.1(3)&nbsp;s | β⁺ (85%) | ⁸⁷Nb | rowspan=2|7/2+# | rowspan=2| | rowspan=2| |- | β⁺, p (15%) | ⁸⁶Zr |-id=Molybdenum-87m | style="text-indent:1em" | ^87mMo | colspan="3" style="text-indent:2em" | 310(30)&nbsp;keV | | | | (1/2−) | | |-id=Molybdenum-88 | ⁸⁸Mo | style="text-align:right" | 42 | style="text-align:right" | 46 | 87.921968(4) | 8.0(2)&nbsp;min | β⁺ | ⁸⁸Nb | 0+ | | |-id=Molybdenum-89 | ⁸⁹Mo | style="text-align:right" | 42 | style="text-align:right" | 47 | 88.919468(4) | 2.11(10)&nbsp;min | β⁺ | ⁸⁹Nb | (9/2+) | | |-id=Molybdenum-89m | style="text-indent:1em" | ^89mMo | colspan="3" style="text-indent:2em" | 387.5(2)&nbsp;keV | 190(15)&nbsp;ms | IT | ⁸⁹Mo | (1/2−) | | |-id=Molybdenum-90 | ⁹⁰Mo | style="text-align:right" | 42 | style="text-align:right" | 48 | 89.913931(4) | 5.56(9)&nbsp;h | β⁺ | ⁹⁰Nb | 0+ | | |-id=Molybdenum-90m | style="text-indent:1em" | ^90mMo | colspan="3" style="text-indent:2em" | 2874.73(15)&nbsp;keV | 1.14(5)&nbsp;μs | IT | ⁹⁰Mo | 8+ | | |-id=Molybdenum-91 | ⁹¹Mo | style="text-align:right" | 42 | style="text-align:right" | 49 | 90.911745(7) | 15.49(1)&nbsp;min | β⁺ | ⁹¹Nb | 9/2+ | | |-id=Molybdenum-91m | rowspan=2 style="text-indent:1em" | ^91mMo | rowspan=2 colspan="3" style="text-indent:2em" | 653.01(9)&nbsp;keV | rowspan=2|64.6(6)&nbsp;s | IT (50.0%) | ⁹¹Mo | rowspan=2|1/2− | rowspan=2| | rowspan=2| |- | β⁺ (50.0%) | ⁹¹Nb |-id=Molybdenum-92 | ⁹²Mo | style="text-align:right" | 42 | style="text-align:right" | 50 | 91.90680715(17) | colspan=3 align=center|Observationally Stable | 0+ | 0.14649(106) | |-id=Molybdenum-92m | style="text-indent:1em" | ^92mMo | colspan="3" style="text-indent:2em" | 2760.52(14)&nbsp;keV | 190(3)&nbsp;ns | IT | ⁹²Mo | 8+ | | |-id=Molybdenum-93 | rowspan=2|⁹³Mo | rowspan=2 style="text-align:right" | 42 | rowspan=2 style="text-align:right" | 51 | rowspan=2|92.90680877(19) | rowspan=2|4839(63)&nbsp;y | EC (95.7%) | ^93mNb | rowspan=2|5/2+ | rowspan=2| | rowspan=2| |- | EC (4.3%) | ⁹³Nb |-id=Molybdenum-93m1 | rowspan=2 style="text-indent:1em" | ^93m1Mo | rowspan=2 colspan="3" style="text-indent:2em" | 2424.95(4)&nbsp;keV | rowspan=2|6.85(7)&nbsp;h | IT (99.88%) | ⁹³Mo | rowspan=2|21/2+ | rowspan=2| | rowspan=2| |- | β⁺ (0.12%) | ⁹³Nb |-id=Molybdenum-93m2 | style="text-indent:1em" | ^93m2Mo | colspan="3" style="text-indent:2em" | 9695(17)&nbsp;keV | 1.8(10)&nbsp;μs | IT | ⁹³Mo | (39/2−) | | |-id=Molybdenum-94 | ⁹⁴Mo | style="text-align:right" | 42 | style="text-align:right" | 52 | 93.90508359(15) | colspan=3 align=center|Stable | 0+ | 0.09187(33) | |-id=Molybdenum-95 | ⁹⁵Mo | style="text-align:right" | 42 | style="text-align:right" | 53 | 94.90583744(13) | colspan=3 align=center|Stable | 5/2+ | 0.15873(30) | |-id=Molybdenum-96 | ⁹⁶Mo | style="text-align:right" | 42 | style="text-align:right" | 54 | 95.90467477(13) | colspan=3 align=center|Stable | 0+ | 0.16673(8) | |-id=Molybdenum-97 | ⁹⁷Mo | style="text-align:right" | 42 | style="text-align:right" | 55 | 96.90601690(18) | colspan=3 align=center|Stable | 5/2+ | 0.09582(15) | |-id=Molybdenum-98 | ⁹⁸Mo | style="text-align:right" | 42 | style="text-align:right" | 56 | 97.90540361(19) | colspan=3 align=center|Observationally Stable | 0+ | 0.24292(80) | |- | ⁹⁹Mo | style="text-align:right" | 42 | style="text-align:right" | 57 | 98.90770730(25) | 65.932(5)&nbsp;h | β^− | ^99mTc | 1/2+ | | |-id=Molybdenum-99m1 | style="text-indent:1em" | ^99m1Mo | colspan="3" style="text-indent:2em" | 97.785(3)&nbsp;keV | 15.5(2)&nbsp;μs | IT | ⁹⁹Mo | 5/2+ | | |-id=Molybdenum-99m2 | style="text-indent:1em" | ^99m2Mo | colspan="3" style="text-indent:2em" | 684.10(19)&nbsp;keV | 760(60)&nbsp;ns | IT | ⁹⁹Mo | 11/2− | | |-id=Molybdenum-100 | ¹⁰⁰Mo | style="text-align:right" | 42 | style="text-align:right" | 58 | 99.9074680(3) | 7.07(14)×10¹⁸&nbsp;y | β^−β^− | ¹⁰⁰Ru | 0+ | 0.09744(65) | |-id=Molybdenum-101 | ¹⁰¹Mo | style="text-align:right" | 42 | style="text-align:right" | 59 | 100.9103376(3) | 14.61(3)&nbsp;min | β^− | ¹⁰¹Tc | 1/2+ | | |-id=Molybdenum-101m1 | style="text-indent:1em" | ^101m1Mo | colspan="3" style="text-indent:2em" | 13.497(9)&nbsp;keV | 226(7)&nbsp;ns | IT | ¹⁰¹Mo | 3/2+ | | |-id=Molybdenum-101m2 | style="text-indent:1em" | ^101m2Mo | colspan="3" style="text-indent:2em" | 57.015(11)&nbsp;keV | 133(70)&nbsp;ns | IT | ¹⁰¹Mo | 5/2+ | | |-id=Molybdenum-102 | ¹⁰²Mo | style="text-align:right" | 42 | style="text-align:right" | 60 | 101.910294(9) | 11.3(2)&nbsp;min | β^− | ¹⁰²Tc | 0+ | | |-id=Molybdenum-103 | ¹⁰³Mo | style="text-align:right" | 42 | style="text-align:right" | 61 | 102.913092(10) | 67.5(15)&nbsp;s | β^− | ¹⁰³Tc | 3/2+ | | |-id=Molybdenum-104 | ¹⁰⁴Mo | style="text-align:right" | 42 | style="text-align:right" | 62 | 103.913747(10) | 60(2)&nbsp;s | β^− | ¹⁰⁴Tc | 0+ | | |-id=Molybdenum-105 | ¹⁰⁵Mo | style="text-align:right" | 42 | style="text-align:right" | 63 | 104.9169798(23) | 36.3(8)&nbsp;s | β^− | ¹⁰⁵Tc | (5/2−) | | |-id=Molybdenum-106 | ¹⁰⁶Mo | style="text-align:right" | 42 | style="text-align:right" | 64 | 105.9182732(98) | 8.73(12)&nbsp;s | β^− | ¹⁰⁶Tc | 0+ | | |-id=Molybdenum-107 | ¹⁰⁷Mo | style="text-align:right" | 42 | style="text-align:right" | 65 | 106.9221198(99) | 3.5(5)&nbsp;s | β^− | ¹⁰⁷Tc | (1/2+) | | |-id=Molybdenum-107m | style="text-indent:1em" | ^107mMo | colspan="3" style="text-indent:2em" | 65.4(2)&nbsp;keV | 445(21)&nbsp;ns | IT | ¹⁰⁷Mo | (5/2+) | | |-id=Molybdenum-108 | rowspan=2|¹⁰⁸Mo | rowspan=2 style="text-align:right" | 42 | rowspan=2 style="text-align:right" | 66 | rowspan=2|107.9240475(99) | rowspan=2|1.105(10)&nbsp;s | β^− (>99.5%) | ¹⁰⁸Tc | rowspan=2|0+ | rowspan=2| | rowspan=2| |- | β^−, n (<0.5%) | ¹⁰⁷Tc |-id=Molybdenum-109 | rowspan=2|¹⁰⁹Mo | rowspan=2 style="text-align:right" | 42 | rowspan=2 style="text-align:right" | 67 | rowspan=2|108.928438(12) | rowspan=2|700(14)&nbsp;ms | β^− (98.7%) | ¹⁰⁹Tc | rowspan=2|(1/2+) | rowspan=2| | rowspan=2| |- | β^−, n (1.3%) | ¹⁰⁸Tc |-id=Molybdenum-109m | style="text-indent:1em" | ^109mMo | colspan="3" style="text-indent:2em" | 69.7(5)&nbsp;keV | 210(60)&nbsp;ns | IT | ¹⁰⁹Mo | 5/2+# | | |-id=Molybdenum-110 | rowspan=2|¹¹⁰Mo | rowspan=2 style="text-align:right" | 42 | rowspan=2 style="text-align:right" | 68 | rowspan=2|109.930718(26) | rowspan=2|292(7)&nbsp;ms | β^− (98.0%) | ¹¹⁰Tc | rowspan=2|0+ | rowspan=2| | rowspan=2| |- | β^−, n (2.0%) | ¹⁰⁹Tc |-id=Molybdenum-111 | rowspan=2|¹¹¹Mo | rowspan=2 style="text-align:right" | 42 | rowspan=2 style="text-align:right" | 69 | rowspan=2|110.935652(14) | rowspan=2|193.6(44)&nbsp;ms | β^− (>88%) | ¹¹¹Tc | rowspan=2|1/2+# | rowspan=2| | rowspan=2| |- | β^−, n (<12%) | ¹¹⁰Tc |-id=Molybdenum-111m | rowspan=2 style="text-indent:1em" | ^111mMo | rowspan=2 colspan="3" style="text-indent:2em" | 100(50)#&nbsp;keV | rowspan=2|~200&nbsp;ms | β^− | ¹¹¹Tc | rowspan=2|7/2−# | rowspan=2| | rowspan=2| |- | β^−, n? | ¹¹⁰Tc |-id=Molybdenum-112 | rowspan=2|¹¹²Mo | rowspan=2 style="text-align:right" | 42 | rowspan=2 style="text-align:right" | 70 | rowspan=2|111.93829(22)# | rowspan=2|125(5)&nbsp;ms | β^− | ¹¹²Tc | rowspan=2|0+ | rowspan=2| | rowspan=2| |- | β^−, n? | ¹¹¹Tc |-id=Molybdenum-113 | rowspan=2|¹¹³Mo | rowspan=2 style="text-align:right" | 42 | rowspan=2 style="text-align:right" | 71 | rowspan=2|112.94348(32)# | rowspan=2|80(2)&nbsp;ms | β^− | ¹¹³Tc | rowspan=2|5/2+# | rowspan=2| | rowspan=2| |- | β^−, n? | ¹¹²Tc |-id=Molybdenum-114 | rowspan=2|¹¹⁴Mo | rowspan=2 style="text-align:right" | 42 | rowspan=2 style="text-align:right" | 72 | rowspan=2|113.94667(32)# | rowspan=2|58(2)&nbsp;ms | β^− | ¹¹⁴Tc | rowspan=2|0+ | rowspan=2| | rowspan=2| |- | β^−, n? | ¹¹³Tc |-id=Molybdenum-115 | rowspan=3|¹¹⁵Mo | rowspan=3 style="text-align:right" | 42 | rowspan=3 style="text-align:right" | 73 | rowspan=3|114.95217(43)# | rowspan=3|45.5(20)&nbsp;ms | β^− | ¹¹⁵Tc | rowspan=3|3/2+# | rowspan=3| | rowspan=3| |- | β^−, n? | ¹¹⁴Tc |- | β^−, 2n? | ¹¹³Tc |-id=Molybdenum-116 | rowspan=3|¹¹⁶Mo | rowspan=3 style="text-align:right" | 42 | rowspan=3 style="text-align:right" | 74 | rowspan=3|115.95576(54)# | rowspan=3|32(4)&nbsp;ms | β^− | ¹¹⁶Tc | rowspan=3|0+ | rowspan=3| | rowspan=3| |- | β^−, n? | ¹¹⁵Tc |- | β^−, 2n? | ¹¹⁴Tc |-id=Molybdenum-117 | rowspan=3|¹¹⁷Mo | rowspan=3 style="text-align:right" | 42 | rowspan=3 style="text-align:right" | 75 | rowspan=3|116.96169(54)# | rowspan=3|22(5)&nbsp;ms | β^− | ¹¹⁷Tc | rowspan=3|3/2+# | rowspan=3| | rowspan=3| |- | β^−, n? | ¹¹⁶Tc |- | β^−, 2n? | ¹¹⁵Tc |-id=Molybdenum-118 | rowspan=3|¹¹⁸Mo | rowspan=3 style="text-align:right" | 42 | rowspan=3 style="text-align:right" | 76 | rowspan=3|117.96525(54)# | rowspan=3|21(6)&nbsp;ms | β^− | ¹¹⁸Tc | rowspan=3|0+ | rowspan=3| | rowspan=3| |- | β^−, n? | ¹¹⁷Tc |- | β^−, 2n? | ¹¹⁶Tc |-id=Molybdenum-119 |rowspan=3| ¹¹⁹Mo |rowspan=3 style="text-align:right" | 42 |rowspan=3 style="text-align:right" | 77 |rowspan=3|118.97147(32)# |rowspan=3| 12#&nbsp;ms<br>[>550&nbsp;ns] | β^−? | ¹¹⁹Tc |rowspan=3|3/2+# |rowspan=3| |rowspan=3| |- | β^−, n? | ¹¹⁸Tc |- | β^−, 2n? | ¹¹⁷Tc

Molybdenum-99

Molybdenum-99 is produced commercially by intense neutron-bombardment (i.e. fission) 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 ⁹⁹Mo is used in these diagnostic medical scans, when actually it has no role in the imaging agent or the scan itself. In fact, ⁹⁹Mo co-eluted with the ^99mTc (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 ⁹⁹Mo concentrations exceeding more than 0.15 μCi/mCi ^99mTc or 0.015% should not be administered for usage in humans. Typically, quantification of ⁹⁹Mo breakthrough is performed for every elution when using a ⁹⁹Mo/^99mTc generator during QA-QC testing of the final product.

There are alternative routes for generating ⁹⁹Mo 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 ¹⁰⁰Mo targets. Historically, ⁹⁹Mo generated by neutron capture on natural isotopic molybdenum or enriched ⁹⁸Mo targets was used for the development of commercial ⁹⁹Mo/^99mTc generators. The neutron-capture process was eventually superseded by fission-based ⁹⁹Mo that could be generated with much higher specific activities. Implementing feed-stocks of high specific activity ⁹⁹Mo solutions thus allowed for higher quality production and better separations of ^99mTc from ⁹⁹Mo on small alumina column using chromatography. Employing low-specific activity ⁹⁹Mo under similar conditions is particularly problematic in that either higher Mo loading capacities or larger columns are required for accommodating equivalent amounts of ⁹⁹Mo. Chemically speaking, this phenomenon occurs due to other Mo isotopes present aside from ⁹⁹Mo that compete for surface site interactions on the column substrate. In turn, low-specific activity ⁹⁹Mo usually requires much larger column sizes and longer separation times, and usually yields ^99mTc accompanied by unsatisfactory amounts of the parent radioisotope when using γ-alumina as the column substrate. Ultimately, the inferior end-product ^99mTc generated under these conditions makes it essentially incompatible with the current supply chain.

In the last decade, cooperative agreements between the US government and private capital entities have resurrected neutron capture production for commercially distributed ⁹⁹Mo/^99mTc in the United States of America. The return to neutron-capture-based ⁹⁹Mo has also been accompanied by the implementation of novel separation methods that allow for low-specific activity ⁹⁹Mo to be utilized.

See also

Daughter products other than molybdenum

• Isotopes of technetium
• Isotopes of niobium
• Isotopes of zirconium

References