Isotopes of molybdenum

Isotopes of molybdenum (₄₂Mo)
γ	–
Standard atomic weight Ar°(Mo)
	95.95±0.01; 95.95±0.01 (abridged);
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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]

Molybdenum-100, with a half-life of approximately 8.5×10¹⁸ y, 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. Molybdenum isotopes with mass numbers 111 and up all have half-lives of approximately .15 s.^[5]

List of isotopes

Nuclide ^{[n 1]}	Z	N	Isotopic mass (Da)^[6] ^{[n 2]}^{[n 3]}	Half-life ^{[n 4]}	Decay mode ^{[n 5]}	Daughter isotope ^{[n 6]}	Spin and parity ^{[n 7]}^{[n 8]}	Natural abundance (mole fraction)
Nuclide ^{[n 1]}	Excitation energy			Half-life ^{[n 4]}	Decay mode ^{[n 5]}	Daughter isotope ^{[n 6]}	Spin and parity ^{[n 7]}^{[n 8]}	Normal proportion	Range of variation
⁸¹Mo	42	39	80.96623(54)#	1# ms	β⁺?	⁸¹Nb	5/2+#
⁸¹Mo	42	39	80.96623(54)#	1# ms	β⁺, p?	⁸⁰Zr	5/2+#
⁸²Mo	42	40	81.95666(43)#	30# ms	β⁺?	⁸²Nb	0+
⁸²Mo	42	40	81.95666(43)#	30# ms	β⁺, p?	⁸¹Zr	0+
⁸³Mo	42	41	82.95025(43)#	23(19) ms [6(+30-3) ms]	β⁺	⁸³Nb	3/2−#
⁸³Mo	42	41	82.95025(43)#	23(19) ms [6(+30-3) ms]	β⁺, p	⁸²Zr	3/2−#
⁸⁴Mo	42	42	83.94185(32)#	3.8(9) ms [3.7(+10-8) s]	β⁺	⁸⁴Nb	0+
⁸⁵Mo	42	43	84.938261(17)	3.2(2) s	β⁺	⁸⁵Nb	(1/2−)#
⁸⁶Mo	42	44	85.931174(3)	19.6(11) s	β⁺	⁸⁶Nb	0+
⁸⁷Mo	42	45	86.928196(3)	14.05(23) s	β⁺ (85%)	⁸⁷Nb	7/2+#
⁸⁷Mo	42	45	86.928196(3)	14.05(23) s	β⁺, p (15%)	⁸⁶Zr	7/2+#
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			1.12(5) μs			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 (50.1%)	⁹¹Mo	1/2−
^91mMo	653.01(9) keV			64.6(6) s	β⁺ (49.9%)	⁹¹Nb	1/2−
⁹²Mo	42	50	91.90680715(17)	Observationally Stable^{[n 9]}			0+	0.14649(106)
^92mMo	2760.46(16) keV			190(3) ns			8+
⁹³Mo	42	51	92.90680877(19)	4839(63) y^[2]	EC	⁹³Nb	5/2+
^93mMo	2424.89(3) keV			6.85(7) h	IT (99.88%)	⁹³Mo	21/2+
^93mMo	2424.89(3) keV			6.85(7) h	β⁺ (.12%)	⁹³Nb	21/2+
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(30)
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)	2.7489(6) d	β⁻	^99mTc	1/2+
^99m1Mo	97.785(3) keV			15.5(2) μs			5/2+
^99m2Mo	684.5(4) keV			0.76(6) μs			11/2−
¹⁰⁰Mo^{[n 13]}^{[n 10]}	42	58	99.9074680(3)	7.07(14)×10¹⁸ a^[1]	β⁻β⁻	¹⁰⁰Ru	0+	0.09744(65)
¹⁰¹Mo	42	59	100.9103376(3)	14.61(3) min	β⁻	¹⁰¹Tc	1/2+
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	104.916982(10)	35.6(16) s	β⁻	¹⁰⁵Tc	(5/2−)
¹⁰⁶Mo	42	64	105.918273(10)	8.73(12) s	β⁻	¹⁰⁶Tc	0+
¹⁰⁷Mo	42	65	106.92212(1)	3.5(5) s	β⁻	¹⁰⁷Tc	(7/2−)
^107mMo	66.3(2) keV			470(30) ns			(5/2−)
¹⁰⁸Mo	42	66	107.924048(10)	1.09(2) s	β⁻	¹⁰⁸Tc	0+
¹⁰⁹Mo	42	67	108.928438(12)	0.53(6) s	β⁻	¹⁰⁹Tc	(7/2−)#
¹¹⁰Mo	42	68	109.930718(26)	0.27(1) s	β⁻ (>99.9%)	¹¹⁰Tc	0+
¹¹⁰Mo	42	68	109.930718(26)	0.27(1) s	β⁻, n (<.1%)	¹⁰⁹Tc	0+
¹¹¹Mo	42	69	110.935652(14)	200# ms [>300 ns]	β⁻	¹¹¹Tc
¹¹²Mo	42	70	111.93829(22)#	150# ms [>300 ns]	β⁻	¹¹²Tc	0+
¹¹³Mo	42	71	112.94348(32)#	100# ms [>300 ns]	β⁻	¹¹³Tc
¹¹⁴Mo	42	72	113.94667(32)#	80# ms [>300 ns]			0+
¹¹⁵Mo	42	73	114.95217(43)#	60# ms [>300 ns]
¹¹⁶Mo	42	74	115.95576(54)#	32(4) ms	β⁻	¹¹⁶Tc	0+
¹¹⁷Mo	42	75	116.96169(54)#	22(5) ms	β⁻	¹¹⁷Tc	3/2+#
¹¹⁸Mo	42	76	117.96525(54)#	21(6) ms	β⁻	¹¹⁸Tc	0+
¹¹⁹Mo	42	77	118.97147(32)#	12# ms	β⁻?	¹¹⁹Tc	3/2+#
					β⁻, n?	¹¹⁸Tc
					β⁻, 2n?	¹¹⁷Tc
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Molybdenum-99

Molybdenum-99 is produced commercially by intense neutron-bombardment of a highly purified uranium-235 target, followed rapidly by extraction.^[7] 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.^[8] 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.^[9]^[10] 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.^[11] 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

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.

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