# Isotopes of ruthenium

Naturally occurring ruthenium ($_{44}$Ru) is composed of seven stable isotopes (of which two may in the future be found radioactive). Additionally, 27 radioactive isotopes have been discovered. Of these radioisotopes, the most stable are $^{106}$Ru, with a half-life of 373.59 days; $^{103}$Ru, with a half-life of 39.26 days and $^{97}$Ru, with a half-life of 2.9 days.
Twenty-four other radioisotopes have been characterized with atomic weights ranging from 86.95 u ($^{87}$Ru) to 119.95 u ($^{120}$Ru). Most of these have half-lives that are less than five minutes, except $^{94}$Ru (half-life: 51.8 minutes), $^{95}$Ru (half-life: 1.643 hours), and $^{105}$Ru (half-life: 4.44 hours).
The primary decay mode before the most abundant isotope, $^{102}$Ru, is electron capture and the primary mode after is beta emission. The primary decay product before $^{102}$Ru is technetium and the primary product after is rhodium.
Because of the very high volatility of ruthenium tetroxide (RuO $_4$) ruthenium radioactive isotopes with their relative short half-life are considered as the second most hazardous gaseous isotopes after iodine-131 in case of release by a nuclear accident. The two most important isotopes of ruthenium in case of nuclear accident are these with the longest half-life: $^{103}$Ru (39.26 days) and $^{106}$Ru (373.59 days).

## 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 |
| $^{85}$Ru | 44 | 41 | 84.96712(54)# | 1# ms [>400 ns] | | | 3/2−# | | |
| $^{86}$Ru | 44 | 42 | 85.95731(43)# | 50# ms [>400 ns] | | | 0+ | | |
| $^{87}$Ru | 44 | 43 | 86.95091(43)# | 50# ms [>1.5 μs] | | | 1/2−# | | |
| $^{88}$Ru | 44 | 44 | 87.94166(32)# | 1.5(3) s | β$^+$ (>96.4%) | $^{88}$Tc | 0+ | | |
| $^{88}$Ru | 44 | 44 | 87.94166(32)# | 1.5(3) s | β$^+$, p (<3.6%) | $^{87}$Mo | 0+ | | |
| $^{89}$Ru | 44 | 45 | 88.937338(26) | 1.32(3) s | β$^+$ (96.7%) | $^{89}$Tc | (9/2+) | | |
| $^{89}$Ru | 44 | 45 | 88.937338(26) | 1.32(3) s | β$^+$, p (3.1%) | $^{88}$Mo | (9/2+) | | |
| $^{90}$Ru | 44 | 46 | 89.9303444(40) | 11.7(9) s | β$^+$ | $^{90}$Tc | 0+ | | |
| $^{91}$Ru | 44 | 47 | 90.9267415(24) | 8.0(4) s | β$^+$ | $^{91}$Tc | (9/2+) | | |
| $^{91m}$Ru | −340(500) keV | −340(500) keV | −340(500) keV | 7.6(8) s | β$^+$ (>99.9%) | $^{91}$Tc | (1/2−) | | |
| $^{91m}$Ru | −340(500) keV | −340(500) keV | −340(500) keV | 7.6(8) s | β$^+$, p (?%) | $^{90}$Mo | (1/2−) | | |
| $^{92}$Ru | 44 | 48 | 91.9202344(29) | 3.65(5) min | β$^+$ | $^{92}$Tc | 0+ | | |
| $^{92m}$Ru | 2833.9(18) keV | 2833.9(18) keV | 2833.9(18) keV | 100(8) ns | IT | $^{92}$Ru | (8+) | | |
| $^{93}$Ru | 44 | 49 | 92.9171044(22) | 59.7(6) s | β$^+$ | $^{93}$Tc | (9/2)+ | | |
| $^{93m1}$Ru | 734.40(10) keV | 734.40(10) keV | 734.40(10) keV | 10.8(3) s | β$^+$ (78.0%) | $^{93}$Tc | (1/2)− | | |
| $^{93m1}$Ru | 734.40(10) keV | 734.40(10) keV | 734.40(10) keV | 10.8(3) s | IT (22.0%) | $^{93}$Ru | (1/2)− | | |
| $^{93m1}$Ru | 734.40(10) keV | 734.40(10) keV | 734.40(10) keV | 10.8(3) s | β$^+$, p (0.027%) | $^{92}$Mo | (1/2)− | | |
| $^{93m2}$Ru | 2082.5(9) keV | 2082.5(9) keV | 2082.5(9) keV | 2.30(7) μs | IT | $^{93}$Ru | (21/2)+ | | |
| $^{94}$Ru | 44 | 50 | 93.9113429(34) | 51.8(6) min | β$^+$ | $^{94}$Tc | 0+ | | |
| $^{94m}$Ru | 2644.1(4) keV | 2644.1(4) keV | 2644.1(4) keV | 67.5(28) μs | IT | $^{94}$Ru | 8+ | | |
| $^{95}$Ru | 44 | 51 | 94.910404(10) | 1.607(4) h | β$^+$ | $^{95}$Tc | 5/2+ | | |
| $^{96}$Ru | 44 | 52 | 95.90758891(18) | Observationally Stable | Observationally Stable | Observationally Stable | 0+ | 0.0554(14) | |
| $^{97}$Ru | 44 | 53 | 96.9075458(30) | 2.8370(14) d | β$^+$ | $^{97}$Tc | 5/2+ | | |
| $^{98}$Ru | 44 | 54 | 97.9052867(69) | Stable | Stable | Stable | 0+ | 0.0187(3) | |
| $^{99}$Ru | 44 | 55 | 98.90593028(37) | Stable | Stable | Stable | 5/2+ | 0.1276(14) | |
| $^{100}$Ru | 44 | 56 | 99.90421046(37) | Stable | Stable | Stable | 0+ | 0.1260(7) | |
| $^{101}$Ru | 44 | 57 | 100.90557309(44) | Stable | Stable | Stable | 5/2+ | 0.1706(2) | |
| $^{101m}$Ru | 527.56(10) keV | 527.56(10) keV | 527.56(10) keV | 17.5(4) μs | IT | $^{101}$Ru | 11/2− | | |
| $^{102}$Ru | 44 | 58 | 101.90434031(45) | Stable | Stable | Stable | 0+ | 0.3155(14) | |
| $^{103}$Ru | 44 | 59 | 102.90631485(47) | 39.245(8) d | β$^−$ | $^{103}$Rh | 3/2+ | | |
| $^{103m}$Ru | 238.2(7) keV | 238.2(7) keV | 238.2(7) keV | 1.69(7) ms | IT | $^{103}$Ru | 11/2− | | |
| $^{104}$Ru | 44 | 60 | 103.9054253(27) | Observationally Stable | Observationally Stable | Observationally Stable | 0+ | 0.1862(27) | |
| $^{105}$Ru | 44 | 61 | 104.9077455(27) | 4.439(11) h | β$^−$ | $^{105}$Rh | 3/2+ | | |
| $^{105m}$Ru | 20.606(14) keV | 20.606(14) keV | 20.606(14) keV | 340(15) ns | IT | $^{105}$Ru | 5/2+ | | |
| $^{106}$Ru | 44 | 62 | 105.9073282(58) | 371.8(18) d | β$^−$ | $^{106}$Rh | 0+ | | |
| $^{107}$Ru | 44 | 63 | 106.9099698(93) | 3.75(5) min | β$^−$ | $^{107}$Rh | (5/2)+ | | |
| $^{108}$Ru | 44 | 64 | 107.9101858(93) | 4.55(5) min | β$^−$ | $^{108}$Rh | 0+ | | |
| $^{109}$Ru | 44 | 65 | 108.9133237(96) | 34.4(2) s | β$^−$ | $^{109}$Rh | (5/2+) | | |
| $^{109m}$Ru | 96.14(15) keV | 96.14(15) keV | 96.14(15) keV | 680(30) ns | IT | $^{109}$Ru | (5/2−) | | |
| $^{110}$Ru | 44 | 66 | 109.9140385(96) | 12.04(17) s | β$^−$ | $^{110}$Rh | 0+ | | |
| $^{111}$Ru | 44 | 67 | 110.917568(10) | 2.12(7) s | β$^−$ | $^{111}$Rh | 5/2+ | | |
| $^{112}$Ru | 44 | 68 | 111.918807(10) | 1.75(7) s | β$^−$ | $^{112}$Rh | 0+ | | |
| $^{113}$Ru | 44 | 69 | 112.922847(41) | 0.80(5) s | β$^−$ | $^{113}$Rh | (1/2+) | | |
| $^{113m}$Ru | 131(33) keV | 131(33) keV | 131(33) keV | 510(30) ms | β$^−$ (?%) | $^{113}$Rh | (7/2−) | | |
| $^{113m}$Ru | 131(33) keV | 131(33) keV | 131(33) keV | 510(30) ms | IT (?%) | $^{113}$Ru | (7/2−) | | |
| $^{114}$Ru | 44 | 70 | 113.9246144(38) | 0.54(3) s | β$^−$ | $^{114}$Rh | 0+ | | |
| $^{115}$Ru | 44 | 71 | 114.929033(27) | 318(19) ms | β$^−$ | $^{115}$Rh | (1/2+) | | |
| $^{115m}$Ru | 82(6) keV | 82(6) keV | 82(6) keV | 76(6) ms | β$^−$ (?%) | $^{115}$Rh | (7/2−) | | |
| $^{115m}$Ru | 82(6) keV | 82(6) keV | 82(6) keV | 76(6) ms | IT (?%) | $^{115}$Ru | (7/2−) | | |
| $^{116}$Ru | 44 | 72 | 115.9312192(40) | 204(6) ms | β$^−$ | $^{116}$Rh | 0+ | | |
| $^{117}$Ru | 44 | 73 | 116.93614(47) | 151(3) ms | β$^−$ | $^{117}$Rh | 3/2+# | | |
| $^{117m}$Ru | 185.0(4) keV | 185.0(4) keV | 185.0(4) keV | 2.49(6) μs | IT | $^{117}$Ru | 7/2−# | | |
| $^{118}$Ru | 44 | 74 | 117.93881(22)# | 99(3) ms | β$^−$ | $^{118}$Rh | 0+ | | |
| $^{119}$Ru | 44 | 75 | 118.94409(32)# | 69.5(20) ms | β$^−$ | $^{119}$Rh | 3/2+# | | |
| $^{119m}$Ru | 227.1(7) keV | 227.1(7) keV | 227.1(7) keV | 384(22) ns | IT | $^{119}$Ru | | | |
| $^{120}$Ru | 44 | 76 | 119.94662(43)# | 45(2) ms | β$^−$ | $^{120}$Rh | 0+ | | |
| $^{121}$Ru | 44 | 77 | 120.95210(43)# | 29(2) ms | β$^−$ | $^{121}$Rh | 3/2+# | | |
| $^{122}$Ru | 44 | 78 | 121.95515(54)# | 25(1) ms | β$^−$ | $^{122}$Rh | 0+ | | |
| $^{123}$Ru | 44 | 79 | 122.96076(54)# | 19(2) ms | β$^−$ | $^{123}$Rh | 3/2+# | | |
| $^{124}$Ru | 44 | 80 | 123.96394(64)# | 15(3) ms | β$^−$ | $^{124}$Rh | 0+ | | |
| $^{125}$Ru | 44 | 81 | 124.96954(32)# | 12# ms [>550 ns] | | | 3/2+# | | |
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* ↑ $^m$Ru – 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).
* 1 2 3 # – 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 $^{96}$Mo with a half-life over 8×10$^{19}$ years
* 1 2 3 4 5 6 Fission product
* ↑ Believed to undergo β$^−$β$^−$ decay to $^{104}$Pd
* In September 2017 an estimated amount of 100 to 300 TBq (0.3 to 1 g) of $^{106}$Ru was released in Russia, probably in the Ural region. It was, after ruling out release from a reentering satellite, concluded that the source is to be found either in nuclear fuel cycle facilities or radioactive source production. In France levels up to 0.036mBq/m$^3$ of air were measured. It is estimated that over distances of the order of a few tens of kilometres around the location of the release levels may exceed the limits for non-dairy foodstuffs.