Isotopes of ruthenium

Isotopes of ruthenium (₄₄Ru)
Standard atomic weight Ar°(Ru)
	101.07±0.02; 101.07±0.02 (abridged);
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Naturally occurring ruthenium (₄₄Ru) is composed of seven stable isotopes: 96, 98-102, 104 (of which the first and last may in the future be found radioactive). Additionally, 27 synthetic radioactive isotopes have been discovered. Of these radioisotopes, the most stable are ¹⁰⁶Ru with a half-life of 371.8 days or 1.018 years, ¹⁰³Ru, with a half-life of 39.245 days, and ⁹⁷Ru with a half-life of 2.837 days.

The other known isotopes run from ⁸⁷Ru to ¹²⁰Ru, and most of these have half-lives that are less than five minutes, except ⁹⁴Ru (51.8 minutes), ⁹⁵Ru (1.607 hours), and ¹⁰⁵Ru (4.44 hours).

The primary decay mode before the most abundant isotope, ¹⁰²Ru, is electron capture to isotopes of technetium, and after beta emission to isotopes of rhodium. Double beta decay is the allowed mode for the two observationally stable isotopes: ⁹⁶Ru and ¹⁰⁴Ru.

Because of the volatility of ruthenium tetroxide (RuO
₄), ruthenium isotopes with relatively short half-life are considered the next most hazardous airborne isotopes, after iodine-131, in case of release by a nuclear accident.^[4]^[5]^[6] The two most important isotopes of ruthenium so released are those with the longest half-life: ¹⁰³Ru ¹⁰⁶Ru.^[5]

List of isotopes

Nuclide ^{[n 1]}	Z	N	Isotopic mass (Da)^[7] ^{[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 4]}	Natural abundance (mole fraction)
Nuclide ^{[n 1]}	Excitation energy^{[n 4]}			Half-life^[1] ^{[n 4]}	Decay mode^[1] ^{[n 5]}	Daughter isotope ^{[n 6]}	Spin and parity^[1] ^{[n 7]}^{[n 4]}	Normal proportion^[1]	Range of variation
⁸⁵Ru	44	41	84.96712(54)#	1# ms [> 400 ns]			3/2−#
⁸⁶Ru	44	42	85.95731(43)#	50# ms [> 400 ns]			0+
⁸⁷Ru	44	43	86.95091(43)#	50# ms [> 1.5 μs]			1/2−#
⁸⁸Ru	44	44	87.94166(32)#	1.5(3) s	β⁺ (>96.4%)	⁸⁸Tc	0+
⁸⁸Ru	44	44	87.94166(32)#	1.5(3) s	β⁺, p (<3.6%)	⁸⁷Mo	0+
⁸⁹Ru	44	45	88.937338(26)	1.32(3) s	β⁺ (96.7%)	⁸⁹Tc	(9/2+)
⁸⁹Ru	44	45	88.937338(26)	1.32(3) s	β⁺, p (3.1%)	⁸⁸Mo	(9/2+)
⁹⁰Ru	44	46	89.9303444(40)	11.7(9) s	β⁺	⁹⁰Tc	0+
⁹¹Ru	44	47	90.9267415(24)	8.0(4) s	β⁺	⁹¹Tc	(9/2+)
^91mRu^{[n 8]}	−340(500) keV			7.6(8) s	β⁺ (>99.9%)	⁹¹Tc	(1/2−)
^91mRu^{[n 8]}	−340(500) keV			7.6(8) s	β⁺, p (?%)	⁹⁰Mo	(1/2−)
⁹²Ru	44	48	91.9202344(29)	3.65(5) min	β⁺	⁹²Tc	0+
^92mRu	2833.9(18) keV			100(8) ns	IT	⁹²Ru	(8+)
⁹³Ru	44	49	92.9171044(22)	59.7(6) s	β⁺	⁹³Tc	(9/2)+
^93m1Ru	734.40(10) keV			10.8(3) s	β⁺ (78.0%)	⁹³Tc	(1/2)−
					IT (22.0%)	⁹³Ru
					β⁺, p (0.027%)	⁹²Mo
^93m2Ru	2082.5(9) keV			2.30(7) μs	IT	⁹³Ru	(21/2)+
⁹⁴Ru	44	50	93.9113429(34)	51.8(6) min	β⁺	⁹⁴Tc	0+
^94mRu	2644.1(4) keV			67.5(28) μs	IT	⁹⁴Ru	8+
⁹⁵Ru	44	51	94.910404(10)	1.607(4) h	β⁺	⁹⁵Tc	5/2+
⁹⁶Ru	44	52	95.90758891(18)	Observationally Stable^{[n 9]}			0+	0.0554(14)
⁹⁷Ru	44	53	96.9075458(30)	2.8370(14) d	β⁺	⁹⁷Tc	5/2+
⁹⁸Ru	44	54	97.9052867(69)	Stable			0+	0.0187(3)
⁹⁹Ru	44	55	98.90593028(37)	Stable			5/2+	0.1276(14)
¹⁰⁰Ru	44	56	99.90421046(37)	Stable			0+	0.1260(7)
¹⁰¹Ru^{[n 10]}	44	57	100.90557309(44)	Stable			5/2+	0.1706(2)
^101mRu	527.56(10) keV			17.5(4) μs	IT	¹⁰¹Ru	11/2−
¹⁰²Ru^{[n 10]}	44	58	101.90434031(45)	Stable			0+	0.3155(14)
¹⁰³Ru^{[n 10]}	44	59	102.90631485(47)	39.245(8) d	β⁻	¹⁰³Rh	3/2+
^103mRu	238.2(7) keV			1.69(7) ms	IT	¹⁰³Ru	11/2−
¹⁰⁴Ru^{[n 10]}	44	60	103.9054253(27)	Observationally Stable^{[n 11]}			0+	0.1862(27)
¹⁰⁵Ru^{[n 10]}	44	61	104.9077455(27)	4.439(11) h	β⁻	¹⁰⁵Rh	3/2+
^105mRu	20.606(14) keV			340(15) ns	IT	¹⁰⁵Ru	5/2+
¹⁰⁶Ru^{[n 10]}	44	62	105.9073282(58)	371.8(18) d	β⁻	¹⁰⁶Rh	0+
¹⁰⁷Ru	44	63	106.9099698(93)	3.75(5) min	β⁻	¹⁰⁷Rh	(5/2)+
¹⁰⁸Ru	44	64	107.9101858(93)	4.55(5) min	β⁻	¹⁰⁸Rh	0+
¹⁰⁹Ru	44	65	108.9133237(96)	34.4(2) s	β⁻	¹⁰⁹Rh	(5/2+)
^109mRu	96.14(15) keV			680(30) ns	IT	¹⁰⁹Ru	(5/2−)
¹¹⁰Ru	44	66	109.9140385(96)	12.04(17) s	β⁻	¹¹⁰Rh	0+
¹¹¹Ru	44	67	110.917568(10)	2.12(7) s	β⁻	¹¹¹Rh	5/2+
¹¹²Ru	44	68	111.918807(10)	1.75(7) s	β⁻	¹¹²Rh	0+
¹¹³Ru	44	69	112.922847(41)	0.80(5) s	β⁻	¹¹³Rh	(1/2+)
^113mRu	131(33) keV			510(30) ms	β⁻ (?%)	¹¹³Rh	(7/2−)
^113mRu	131(33) keV			510(30) ms	IT (?%)	¹¹³Ru	(7/2−)
¹¹⁴Ru	44	70	113.9246144(38)	0.54(3) s	β⁻	¹¹⁴Rh	0+
¹¹⁵Ru	44	71	114.929033(27)	318(19) ms	β⁻	¹¹⁵Rh	(1/2+)
^115mRu	82(6) keV			76(6) ms	β⁻ (?%)	¹¹⁵Rh	(7/2−)
^115mRu	82(6) keV			76(6) ms	IT (?%)	¹¹⁵Ru	(7/2−)
¹¹⁶Ru	44	72	115.9312192(40)	204(6) ms	β⁻	¹¹⁶Rh	0+
¹¹⁷Ru	44	73	116.93614(47)	151(3) ms	β⁻	¹¹⁷Rh	3/2+#
^117mRu	185.0(4) keV			2.49(6) μs	IT	¹¹⁷Ru	7/2−#
¹¹⁸Ru	44	74	117.93881(22)#	99(3) ms	β⁻	¹¹⁸Rh	0+
¹¹⁹Ru	44	75	118.94409(32)#	69.5(20) ms	β⁻	¹¹⁹Rh	3/2+#
^119mRu	227.1(7) keV			384(22) ns	IT	¹¹⁹Ru
¹²⁰Ru	44	76	119.94662(43)#	45(2) ms	β⁻	¹²⁰Rh	0+
¹²¹Ru	44	77	120.95210(43)#	29(2) ms	β⁻	¹²¹Rh	3/2+#
¹²²Ru	44	78	121.95515(54)#	25(1) ms	β⁻	¹²²Rh	0+
¹²³Ru	44	79	122.96076(54)#	19(2) ms	β⁻	¹²³Rh	3/2+#
¹²⁴Ru	44	80	123.96394(64)#	15(3) ms	β⁻	¹²⁴Rh	0+
¹²⁵Ru	44	81	124.96954(32)#	12# ms [> 550 ns]			3/2+#
This table header & footer: view

^ ^mRu – 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).
^ ^a ^b ^c # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
^ Modes of decay:

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 ⁹⁶Mo with a half-life over 8×10¹⁹ years
^ ^a ^b ^c ^d ^e ^f Fission product
^ Believed to undergo β⁻β⁻ decay to ¹⁰⁴Pd

Alleged ruthenium-106 leak

In September 2017 an estimated amount of 100 to 300 TBq (0.3 to 1 g) of ¹⁰⁶Ru was released in Russia, probably in the Ural region. It was, after ruling out release from a reentering satellite, concluded that the source was either in nuclear fuel cycle facilities or radioactive source production. In France levels up to 0.036mBq/m³ of air were measured. It was estimated that for distances of the order of a few tens of kilometres, contamination levels may have exceeded the limits for non-dairy foodstuffs.^[8]

Asteroid that ended the Cretaceous period

The ratios of the amounts of ruthenium isotopes were used to determine the age of the asteroid which exterminated the dinosaurs at the end of the Cretaceous period, and to show that it originated beyond Jupiter in the outer solar system.^[9]

References

^ ^a ^b ^c ^d ^e 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.
^ "Standard Atomic Weights: Ruthenium". CIAAW. 1983.
^ 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.
^ Ronneau, C., Cara, J., & Rimski-Korsakov, A. (1995). Oxidation-enhanced emission of ruthenium from nuclear fuel. Journal of Environmental Radioactivity, 26(1), 63-70.
^ ^a ^b Backman, U., Lipponen, M., Auvinen, A., Jokiniemi, J., & Zilliacus, R. (2004). Ruthenium behaviour in severe nuclear accident conditions. Final report (No. NKS–100). Nordisk Kernesikkerhedsforskning.
^ Beuzet, E., Lamy, J. S., Perron, H., Simoni, E., & Ducros, G. (2012). Ruthenium release modelling in air and steam atmospheres under severe accident conditions using the MAAP4 code^{[dead link]}. Nuclear Engineering and Design, 246, 157-162.
^ 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.
^ [1] Detection of ruthenium 106 in France and in Europe, IRSN France (9 Nov 2017)
^ Dunham, Will (15 August 2024). "Asteroid that doomed the dinosaurs originated beyond Jupiter". The Globe and Mail. Retrieved 8 July 2025. ruthenium shows distinct isotopic compositions between inner and outer solar system materials

[7] Ru – Excited nuclear isomer.

[9] ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.

[TMS-10] # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).

[TNN-11] # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).

[12] Modes of decay:

IT: Isomeric transition

n: Neutron emission

p: Proton emission

[13] Bold symbol as daughter – Daughter product is stable.

[14] ( ) spin value – Indicates spin with weak assignment arguments.

[order-15] Order of ground state and isomer is uncertain.

[16] Believed to undergo β⁺β⁺ decay to ⁹⁶Mo with a half-life over 8×10¹⁹ years

[FP-17] ^ ^a ^b ^c ^d ^e ^f Fission product

[18] Believed to undergo β⁻β⁻ decay to ¹⁰⁴Pd

[NUBASE2020-1] 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.

[CIAAWruthenium-2] "Standard Atomic Weights: Ruthenium". CIAAW. 1983.

[CIAAW2021-3] 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.

[Ronneau_1995-4] Ronneau, C., Cara, J., & Rimski-Korsakov, A. (1995). Oxidation-enhanced emission of ruthenium from nuclear fuel. Journal of Environmental Radioactivity, 26(1), 63-70.

[Backman_2004-5] Backman, U., Lipponen, M., Auvinen, A., Jokiniemi, J., & Zilliacus, R. (2004). Ruthenium behaviour in severe nuclear accident conditions. Final report (No. NKS–100). Nordisk Kernesikkerhedsforskning.

[Beuzet_2012-6] Beuzet, E., Lamy, J. S., Perron, H., Simoni, E., & Ducros, G. (2012). Ruthenium release modelling in air and steam atmospheres under severe accident conditions using the MAAP4 code^{[dead link]}. Nuclear Engineering and Design, 246, 157-162.

[AME2020_II-8] 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.

[19] [1] Detection of ruthenium 106 in France and in Europe, IRSN France (9 Nov 2017)

[20] Dunham, Will (15 August 2024). "Asteroid that doomed the dinosaurs originated beyond Jupiter". The Globe and Mail. Retrieved 8 July 2025. ruthenium shows distinct isotopic compositions between inner and outer solar system materials

[1]

[2]

[3]

[4]

[5]

[6]

[n 1]

[7]

[n 2]

[n 3]

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[n 5]

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[9]

Isotopes of ruthenium

List of isotopes

Alleged ruthenium-106 leak

Asteroid that ended the Cretaceous period

See also

References