Isotopes of molybdenum

"Mo-99" redirects here. For MO99 Freon mix R438A, see refrigerant.

Molybdenum (₄₂Mo) 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.^[5]

Isotopes of molybdenum (₄₂Mo)

Main isotopes[1] Decay abun­dance half-life (t1/2) mode pro­duct 92Mo 14.7% stable 93Mo synth 4839 y[2] ε 93Nb 94Mo 9.19% stable 95Mo 15.9% stable 96Mo 16.7% stable 97Mo 9.58% stable 98Mo 24.3% stable 99Mo synth 65.94 h β− 99mTc γ – 100Mo 9.74% 7.07×1018 y[1] β−β− 100Ru
Standard atomic weight Ar°(Mo)
	95.95±0.01[3] 95.95±0.01 (abridged)[4]
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Molybdenum-100, with a half-life of 7.07×10¹⁸ 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 [n 1]	Z	N	Isotopic mass (Da)[6] [n 2][n 3]	Half-life[1] [n 4]	Decay mode[1] [n 5]	Daughter isotope [n 6]	Spin and parity[1] [n 7][n 8]	Natural abundance (mole fraction)
	Excitation energy							Normal proportion[1]	Range of variation
81Mo	42	39	80.96623(54)#	1# ms [>400 ns]	β+?	81Nb	5/2+#
					β+, p?	80Zr
82Mo	42	40	81.95666(43)#	30# ms [>400 ns]	β+?	82Nb	0+
					β+, p?	81Zr
83Mo	42	41	82.95025(43)#	23(19) ms	β+	83Nb	3/2−#
					β+, p?	82Zr
84Mo	42	42	83.94185(32)#	2.3(3) s	β+	84Nb	0+
					β+, p?	83Zr
85Mo	42	43	84.938261(17)	3.2(2) s	β+ (99.86%)	85Nb	(1/2+)
					β+, p (0.14%)	84Zr
86Mo	42	44	85.931174(3)	19.1(3) s	β+	86Nb	0+
87Mo	42	45	86.928196(3)	14.1(3) s	β+ (85%)	87Nb	7/2+#
					β+, p (15%)	86Zr
88Mo	42	46	87.921968(4)	8.0(2) min	β+	88Nb	0+
89Mo	42	47	88.919468(4)	2.11(10) min	β+	89Nb	(9/2+)
89mMo	387.5(2) keV			190(15) ms	IT	89Mo	(1/2−)
90Mo	42	48	89.913931(4)	5.56(9) h	β+	90Nb	0+
90mMo	2874.73(15) keV			1.14(5) μs	IT	90Mo	8+
91Mo	42	49	90.911745(7)	15.49(1) min	β+	91Nb	9/2+
91mMo	653.01(9) keV			64.6(6) s	IT (50.0%)	91Mo	1/2−
					β+ (50.0%)	91Nb
92Mo	42	50	91.90680715(17)	Observationally Stable[n 9]			0+	0.14649(106)
92mMo	2760.52(14) keV			190(3) ns	IT	92Mo	8+
93Mo	42	51	92.90680877(19)	4839(63) y[2]	EC (95.7%)	93mNb	5/2+
					EC (4.3%)	93Nb
93m1Mo	2424.95(4) keV			6.85(7) h	IT (99.88%)	93Mo	21/2+
					β+ (0.12%)	93Nb
93m2Mo	9695(17) keV			1.8(10) μs	IT	93Mo	(39/2−)
94Mo	42	52	93.90508359(15)	Stable			0+	0.09187(33)
95Mo[n 10]	42	53	94.90583744(13)	Stable			5/2+	0.15873(30)
96Mo	42	54	95.90467477(13)	Stable			0+	0.16673(8)
97Mo[n 10]	42	55	96.90601690(18)	Stable			5/2+	0.09582(15)
98Mo[n 10]	42	56	97.90540361(19)	Observationally Stable[n 11]			0+	0.24292(80)
99Mo[n 10][n 12]	42	57	98.90770730(25)	65.932(5) h	β−	99mTc	1/2+
99m1Mo	97.785(3) keV			15.5(2) μs	IT	99Mo	5/2+
99m2Mo	684.10(19) keV			760(60) ns	IT	99Mo	11/2−
100Mo[n 13][n 10]	42	58	99.9074680(3)	7.07(14)×1018 y	β−β−	100Ru	0+	0.09744(65)
101Mo	42	59	100.9103376(3)	14.61(3) min	β−	101Tc	1/2+
101m1Mo	13.497(9) keV			226(7) ns	IT	101Mo	3/2+
101m2Mo	57.015(11) keV			133(70) ns	IT	101Mo	5/2+
102Mo	42	60	101.910294(9)	11.3(2) min	β−	102Tc	0+
103Mo	42	61	102.913092(10)	67.5(15) s	β−	103Tc	3/2+
104Mo	42	62	103.913747(10)	60(2) s	β−	104Tc	0+
105Mo	42	63	104.9169798(23)[7]	36.3(8) s	β−	105Tc	(5/2−)
106Mo	42	64	105.9182732(98)	8.73(12) s	β−	106Tc	0+
107Mo	42	65	106.9221198(99)	3.5(5) s	β−	107Tc	(1/2+)
107mMo	65.4(2) keV			445(21) ns	IT	107Mo	(5/2+)
108Mo	42	66	107.9240475(99)	1.105(10) s	β− (>99.5%)	108Tc	0+
					β−, n (<0.5%)	107Tc
109Mo	42	67	108.928438(12)	700(14) ms	β− (98.7%)	109Tc	(1/2+)
					β−, n (1.3%)	108Tc
109mMo	69.7(5) keV			210(60) ns	IT	109Mo	5/2+#
110Mo	42	68	109.930718(26)	292(7) ms	β− (98.0%)	110Tc	0+
					β−, n (2.0%)	109Tc
111Mo	42	69	110.935652(14)	193.6(44) ms	β− (>88%)	111Tc	1/2+#
					β−, n (<12%)	110Tc
111mMo	100(50)# keV			~200 ms	β−	111Tc	7/2−#
					β−, n?	110Tc
112Mo	42	70	111.93829(22)#	125(5) ms	β−	112Tc	0+
					β−, n?	111Tc
113Mo	42	71	112.94348(32)#	80(2) ms	β−	113Tc	5/2+#
					β−, n?	112Tc
114Mo	42	72	113.94667(32)#	58(2) ms	β−	114Tc	0+
					β−, n?	113Tc
115Mo	42	73	114.95217(43)#	45.5(20) ms	β−	115Tc	3/2+#
					β−, n?	114Tc
					β−, 2n?	113Tc
116Mo	42	74	115.95576(54)#	32(4) ms	β−	116Tc	0+
					β−, n?	115Tc
					β−, 2n?	114Tc
117Mo	42	75	116.96169(54)#	22(5) ms	β−	117Tc	3/2+#
					β−, n?	116Tc
					β−, 2n?	115Tc
118Mo	42	76	117.96525(54)#	21(6) ms	β−	118Tc	0+
					β−, n?	117Tc
					β−, 2n?	116Tc
119Mo	42	77	118.97147(32)#	12# ms [>550 ns]	β−?	119Tc	3/2+#
					β−, n?	118Tc
					β−, 2n?	117Tc
This table header & footer: view

1. ^mMb – Excited nuclear isomer.
2. ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
3. # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
4. Bold half-life – nearly stable, half-life longer than age of universe.
5. Modes of decay:

   EC:	Electron capture
   IT:	Isomeric transition
   n:	Neutron emission
   p:	Proton emission

6. Bold symbol as daughter – Daughter product is stable.
7. ( ) spin value – Indicates spin with weak assignment arguments.
8. # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
9. Believed to decay by β⁺β⁺ to ⁹²Zr with a half-life over 1.9×10²⁰ y
10. Fission product
11. Believed to decay by β⁻β⁻ to ⁹⁸Ru with a half-life of over 1×10¹⁴ years
12. Used to produce the medically useful radioisotope technetium-99m
13. Primordial radionuclide

Molybdenum-99

Molybdenum-99 is produced commercially by intense neutron-bombardment of a highly purified uranium-235 target, followed rapidly by extraction.^[8] 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.^[9] 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.^[10][11] 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 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 ⁹⁹Mo/^99mTc in the United States of America.^[12] 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.

References

1. Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
2. Kajan, I.; Heinitz, S.; Kossert, K.; Sprung, P.; Dressler, R.; Schumann, D. (2021-10-05). "First direct determination of the ⁹³Mo half-life". Scientific Reports. 11 (1). doi:10.1038/s41598-021-99253-5. ISSN 2045-2322. PMC 8492754. PMID 34611245.
3. "Standard Atomic Weights: Molybdenum". CIAAW. 2013.
4. Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
5. Lide, David R., ed. (2006). CRC Handbook of Chemistry and Physics (87th ed.). Boca Raton, Florida: CRC Press. Section 11. ISBN 978-0-8493-0487-3.
6. Wang, Meng; Huang, W.J.; Kondev, F.G.; Audi, G.; Naimi, S. (2021). "The AME 2020 atomic mass evaluation (II). Tables, graphs and references*". Chinese Physics C. 45 (3): 030003. doi:10.1088/1674-1137/abddaf.
7. Jaries, A.; Stryjczyk, M.; Kankainen, A.; Ayoubi, L. Al; Beliuskina, O.; Canete, L.; de Groote, R. P.; Delafosse, C.; Delahaye, P.; Eronen, T.; Flayol, M.; Ge, Z.; Geldhof, S.; Gins, W.; Hukkanen, M.; Imgram, P.; Kahl, D.; Kostensalo, J.; Kujanpää, S.; Kumar, D.; Moore, I. D.; Mougeot, M.; Nesterenko, D. A.; Nikas, S.; Patel, D.; Penttilä, H.; Pitman-Weymouth, D.; Pohjalainen, I.; Raggio, A.; Ramalho, M.; Reponen, M.; Rinta-Antila, S.; de Roubin, A.; Ruotsalainen, J.; Srivastava, P. C.; Suhonen, J.; Vilen, M.; Virtanen, V.; Zadvornaya, A. "Physical Review C - Accepted Paper: Isomeric states of fission fragments explored via Penning trap mass spectrometry at IGISOL". journals.aps.org. arXiv:2403.04710.
8. Frank N. Von Hippel; Laura H. Kahn (December 2006). "Feasibility of Eliminating the Use of Highly Enriched Uranium in the Production of Medical Radioisotopes". Science & Global Security. 14 (2 & 3): 151–162. Bibcode:2006S&GS...14..151V. doi:10.1080/08929880600993071. S2CID 122507063.
9. Ibrahim I, Zulkifli H, Bohari Y, Zakaria I, Wan Hamirul BWK. Minimizing Molybdenum-99 Contamination In Technetium-99m Pertechnetate From The Elution Of ⁹⁹Mo/^99mTc Generator (PDF) (Report).
10. Richards, P. (1989). Technetium-99m: The early days. 3rd International Symposium on Technetium in Chemistry and Nuclear Medicine, Padova, Italy, 5-8 Sep 1989. OSTI 5612212.
11. Richards, P. (1965-10-14). The Technetium-99m Generator (Report). doi:10.2172/4589063. OSTI 4589063.
12. "Emerging leader with new solutions in the field of nuclear medicine technology". NorthStar Medical Radioisotopes, LLC. Retrieved 2020-01-23.

• Isotopic compositions and standard atomic masses from:
  • de Laeter, John Robert; Böhlke, John Karl; De Bièvre, Paul; Hidaka, Hiroshi; Peiser, H. Steffen; Rosman, Kevin J. R.; Taylor, Philip D. P. (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry. 75 (6): 683–800. doi:10.1351/pac200375060683.
  • Wieser, Michael E. (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry. 78 (11): 2051–2066. doi:10.1351/pac200678112051.
• "News & Notices: Standard Atomic Weights Revised". International Union of Pure and Applied Chemistry. 19 October 2005.
• Half-life, spin, and isomer data selected from the following sources.
  • Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
  • National Nuclear Data Center. "NuDat 2.x database". Brookhaven National Laboratory.
  • Holden, Norman E. (2004). "11. Table of the Isotopes". In Lide, David R. (ed.). CRC Handbook of Chemistry and Physics (85th ed.). Boca Raton, Florida: CRC Press. ISBN 978-0-8493-0485-9.