Isotopes of palladium

Natural palladium (46Pd) is composed of six stable isotopes, 102Pd, 104Pd, 105Pd, 106Pd, 108Pd, and 110Pd, although 102Pd and 110Pd are theoretically unstable. The most stable radioisotopes are 107Pd with a half-life of 6.5 million years, 103Pd with a half-life of 17 days, and 100Pd with a half-life of 3.63 days. Twenty-three other radioisotopes have been characterized with atomic weights ranging from 90.949 u (91Pd) to 128.96 u (129Pd). Most of these have half-lives that are less than a half an hour except 101Pd (half-life: 8.47 hours), 109Pd (half-life: 13.7 hours), and 112Pd (half-life: 21 hours).

Isotopes of palladium (46Pd)
Main isotopes[1] Decay
abun­dance half-life (t1/2) mode pro­duct
100Pd synth 3.63 d ε 100Rh
γ –
102Pd 1.02% stable
103Pd synth 16.991 d ε 103Rh
104Pd 11.1% stable
105Pd 22.3% stable
106Pd 27.3% stable
107Pd trace 6.5×106 y β− 107Ag
108Pd 26.5% stable
110Pd 11.7% stable
Standard atomic weight Ar°(Pd)

The primary decay mode before the most abundant stable isotope, 106Pd, is electron capture and the primary mode after is beta decay. The primary decay product before 106Pd is rhodium and the primary product after is silver.

Radiogenic 107Ag is a decay product of 107Pd and was first discovered in the Santa Clara meteorite of 1978.[4] The discoverers suggest that the coalescence and differentiation of iron-cored small planets may have occurred 10 million years after a nucleosynthetic event. 107Pd versus Ag correlations observed in bodies, which have clearly been melted since accretion of the Solar System, must reflect the presence of short-lived nuclides in the early Solar System.[5]

List of isotopes
Nuclide
[n 1]		 Z N Isotopic mass (Da)
[n 2][n 3]		 Half-life
[n 4]		 Decay
mode
[n 5]		 Daughter
isotope
[n 6]		 Spin and
parity
[n 7][n 4]		 Natural abundance (mole fraction)
Excitation energy[n 4] Normal proportion Range of variation
91Pd 46 45 90.94911(61)# 10# ms [>1.5 μs] β+ 91Rh 7/2+#
92Pd 46 46 91.94042(54)# 1.1(3) s [0.7(+4−2) s] β+ 92Rh 0+
93Pd 46 47 92.93591(43)# 1.07(12) s β+ 93Rh (9/2+)
93mPd 0+X keV 9.3(+25−17) s
94Pd 46 48 93.92877(43)# 9.0(5) s β+ 94Rh 0+
94mPd 4884.4(5) keV 530(10) ns (14+)
95Pd 46 49 94.92469(43)# 10# s β+ 95Rh 9/2+#
95mPd 1860(500)# keV 13.3(3) s β+ (94.1%) 95Rh (21/2+)
IT (5%) 95Pd
β+, p (.9%) 94Ru
96Pd 46 50 95.91816(16) 122(2) s β+ 96Rh 0+
96mPd 2530.8(1) keV 1.81(1) μs 8+
97Pd 46 51 96.91648(32) 3.10(9) min β+ 97Rh 5/2+#
98Pd 46 52 97.912721(23) 17.7(3) min β+ 98Rh 0+
99Pd 46 53 98.911768(16) 21.4(2) min β+ 99Rh (5/2)+
100Pd 46 54 99.908506(12) 3.63(9) d EC 100Rh 0+
101Pd 46 55 100.908289(19) 8.47(6) h β+ 101Rh 5/2+
102Pd 46 56 101.905609(3) Observationally Stable[n 8] 0+ 0.0102(1)
103Pd[n 9] 46 57 102.906087(3) 16.991(19) d EC 103Rh 5/2+
103mPd 784.79(10) keV 25(2) ns 11/2−
104Pd 46 58 103.904036(4) Stable 0+ 0.1114(8)
105Pd[n 10] 46 59 104.905085(4) Stable 5/2+ 0.2233(8)
106Pd[n 10] 46 60 105.903486(4) Stable 0+ 0.2733(3)
107Pd[n 11] 46 61 106.905133(4) 6.5(3)×106 y β− 107Ag 5/2+ trace[n 12]
107m1Pd 115.74(12) keV 0.85(10) μs 1/2+
107m2Pd 214.6(3) keV 21.3(5) s IT 107Pd 11/2−
108Pd[n 10] 46 62 107.903892(4) Stable 0+ 0.2646(9)
109Pd[n 10] 46 63 108.905950(4) 13.7012(24) h β− 109mAg 5/2+
109m1Pd 113.400(10) keV 380(50) ns 1/2+
109m2Pd 188.990(10) keV 4.696(3) min IT 109Pd 11/2−
110Pd[n 10] 46 64 109.905153(12) Observationally Stable[n 13] 0+ 0.1172(9)
111Pd 46 65 110.907671(12) 23.4(2) min β− 111mAg 5/2+
111mPd 172.18(8) keV 5.5(1) h IT 111Pd 11/2−
β− 111mAg
112Pd 46 66 111.907314(19) 21.03(5) h β− 112Ag 0+
113Pd 46 67 112.91015(4) 93(5) s β− 113mAg (5/2+)
113mPd 81.1(3) keV 0.3(1) s IT 113Pd (9/2−)
114Pd 46 68 113.910363(25) 2.42(6) min β− 114Ag 0+
115Pd 46 69 114.91368(7) 25(2) s β− 115mAg (5/2+)#
115mPd 89.18(25) keV 50(3) s β− (92%) 115Ag (11/2−)#
IT (8%) 115Pd
116Pd 46 70 115.91416(6) 11.8(4) s β− 116Ag 0+
117Pd 46 71 116.91784(6) 4.3(3) s β− 117mAg (5/2+)
117mPd 203.2(3) keV 19.1(7) ms IT 117Pd (11/2−)#
118Pd 46 72 117.91898(23) 1.9(1) s β− 118Ag 0+
119Pd 46 73 118.92311(32)# 0.92(13) s β− 119Ag
120Pd 46 74 119.92469(13) 0.5(1) s β− 120Ag 0+
121Pd 46 75 120.92887(54)# 285 ms β− 121Ag
122Pd 46 76 121.93055(43)# 175 ms [>300 ns] β− 122Ag 0+
123Pd 46 77 122.93493(64)# 108 ms β− 123Ag
124Pd 46 78 123.93688(54)# 38 ms β− 124Ag 0+
125Pd[6] 46 79 57 ms β− 125Ag
126Pd[7][8] 46 80 48.6 ms β− 126Ag 0+
126m1Pd 2023 keV 330 ns IT 126Pd 5−
126m2Pd 2110 keV 440 ns IT 126m1Pd 7−
127Pd 46 81 38 ms β− 127Ag
128Pd[7][8] 46 82 35 ms β− 128Ag 0+
128mPd 2151 keV 5.8 μs IT 128Pd 8+
129Pd 46 83 31 ms β− 129Ag
This table header & footer:
  1. mPd – 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. # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
  5. Modes of decay:
    EC:Electron capture
    IT:Isomeric transition
    p:Proton emission
  6. Bold symbol as daughter – Daughter product is stable.
  7. ( ) spin value – Indicates spin with weak assignment arguments.
  8. Believed to decay by β+β+ to 102Ru
  9. Used in medicine
  10. Fission product
  11. Long-lived fission product
  12. Cosmogenic nuclide, also found as nuclear contamination
  13. Believed to decay by β−β− to 110Cd with a half-life over 6×1017 years

Palladium-103

Palladium-103 is a radioisotope of the element palladium that has uses in radiation therapy for prostate cancer and uveal melanoma. Palladium-103 may be created from palladium-102 or from rhodium-103 using a cyclotron. Palladium-103 has a half-life of 16.99[9] days and decays by electron capture to rhodium-103, emitting characteristic x-rays with 21 keV of energy.

Palladium-107
Long-lived fission products
Nuclide t1⁄2 Yield Q[a 1] βγ
(Ma) (%)[a 2] (keV)
99Tc 0.2116.1385294 β
126Sn 0.2300.10844050[a 3] βγ
79Se 0.3270.0447151 β
135Cs 1.33 6.9110[a 4]269 β
93Zr 1.53 5.457591 βγ
107Pd 6.5  1.249933 β
129I 15.7  0.8410194 βγ
  1. Decay energy is split among β, neutrino, and γ if any.
  2. Per 65 thermal neutron fissions of 235U and 35 of 239Pu.
  3. Has decay energy 380 keV, but its decay product 126Sb has decay energy 3.67 MeV.
  4. Lower in thermal reactors because 135Xe, its predecessor, readily absorbs neutrons.

Palladium-107 is the second-longest lived (half-life of 6.5 million years[9]) and least radioactive (decay energy only 33 keV, specific activity 5×10−5 Ci/g) of the 7 long-lived fission products. It undergoes pure beta decay (without gamma radiation) to 107Ag, which is stable.

Its yield from thermal neutron fission of uranium-235 is 0.1629% per fission, only 1/4 that of iodine-129, and only 1/40 those of 99Tc, 93Zr, and 135Cs. Yield from 233U is slightly lower, but yield from 239Pu is much higher, 3.3%. Fast fission or fission of some heavier actinides[which?] will produce palladium-107 at higher yields.

One source[10] estimates that palladium produced from fission contains the isotopes 104Pd (16.9%),105Pd (29.3%), 106Pd (21.3%), 107Pd (17%), 108Pd (11.7%) and 110Pd (3.8%). According to another source, the proportion of 107Pd is 9.2% for palladium from thermal neutron fission of 235U, 11.8% for 233U, and 20.4% for 239Pu (and the 239Pu yield of palladium is about 10 times that of 235U).

Because of this dilution and because 105Pd has 11 times the neutron absorption cross section, 107Pd is not amenable to disposal by nuclear transmutation. However, as a noble metal, palladium is not as mobile in the environment as iodine or technetium.

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. "Standard Atomic Weights: Palladium". CIAAW. 1979.
  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.
  4. W. R. Kelly; G. J. Wasserburg (1978). "Evidence for the existence of 107Pd in the early solar system". Geophysical Research Letters. 5 (12): 1079–1082. Bibcode:1978GeoRL...5.1079K. doi:10.1029/GL005i012p01079.
  5. J. H. Chen; G. J. Wasserburg (1990). "The isotopic composition of Ag in meteorites and the presence of 107Pd in protoplanets". Geochimica et Cosmochimica Acta. 54 (6): 1729–1743. Bibcode:1990GeCoA..54.1729C. doi:10.1016/0016-7037(90)90404-9.
  6. Future Plan of the Experimental Program on Synthesizing the Heaviest Element at RIKEN, Kosuke Morita Archived September 17, 2012, at the Wayback Machine
  7. H. Watanabe; et al. (2013-10-08). "Isomers in 128Pd and 126Pd: Evidence for a Robust Shell Closure at the Neutron Magic Number 82 in Exotic Palladium Isotopes" (PDF). Physical Review Letters. 111 (15): 152501. Bibcode:2013PhRvL.111o2501W. doi:10.1103/PhysRevLett.111.152501. hdl:2437/215438. PMID 24160593.
  8. "Experiments on neutron-rich atomic nuclei could help scientists to understand nuclear reactions in exploding stars". phys.org. 2013-11-29.
  9. Winter, Mark. "Isotopes of palladium". WebElements. The University of Sheffield and WebElements Ltd, UK. Retrieved 4 March 2013.
  10. R. P. Bush (1991). "Recovery of Platinum Group Metals from High Level Radioactive Waste" (PDF). Platinum Metals Review. 35 (4): 202–208. Archived from the original (PDF) on 2015-09-24. Retrieved 2011-04-02.
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