Isotopes of palladium

Naturally occurring 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).

Main isotopes of palladium (₄₆Pd)

Iso­tope Decay abun­dance half-life (t1/2) mode pro­duct ^100Pd syn 3.63 d ε ^100Rh γ – ^102Pd 1.02% stable ^103Pd syn 16.991 d ε ^103Rh ^104Pd 11.14% stable ^105Pd 22.33% stable ^106Pd 27.33% stable ^107Pd trace 6.5×10^6 y β^− ^107Ag ^108Pd 26.46% stable ^110Pd 11.72% stable
Standard atomic weight Ar, standard(Pd)	106.42(1)[1]

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.[2] 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.[3]

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)×10^6 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[4]	46	79		57 ms	β^−	^125Ag
^126Pd[5][6]	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[5][6]	46	82		35 ms	β^−	^128Ag	0+
^128mPd	2151 keV			5.8 µs	IT	^128Pd	8+
^129Pd	46	83		31 ms	β^−	^129Ag

1. ^mPa – 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[7] 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	t​^1⁄2	Yield	Decay energy[a 1]	Decay mode
	(Ma)	(%)[a 2]	(keV)
^99Tc	0.211	6.1385	294	β
^126Sn	0.230	0.1084	4050[a 3]	βγ
^79Se	0.327	0.0447	151	β
^93Zr	1.53	5.4575	91	βγ
^135Cs	2.3	6.9110[a 4]	269	β
^107Pd	6.5	1.2499	33	β
^129I	15.7	0.8410	194	βγ
Decay energy is split among β, neutrino, and γ if any. Per 65 thermal-neutron fissions of U-235 and 35 of Pu-239. Has decay energy 380 keV, but decay product Sb-126 has decay energy 3.67 MeV. Lower in thermal reactor because predecessor absorbs neutrons.

Palladium-107 is the second-longest lived (half-life of 6.5 million years[7]) 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[8] 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

• Patent application for Palladium-103 implantable radiation-delivery device (accessed 12/7/05)

1. Meija, Juris; et al. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure and Applied Chemistry. 88 (3): 265–91. doi:10.1515/pac-2015-0305.
2. 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.
3. 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.
4. Future Plan of the Experimental Program on Synthesizing the Heaviest Element at RIKEN, Kosuke Morita Archived September 17, 2012, at the Wayback Machine
5. 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.
6. "Experiments on neutron-rich atomic nuclei could help scientists to understand nuclear reactions in exploding stars". phys.org. 2013-11-29.
7. Winter, Mark. "Isotopes of palladium". WebElements. The University of Sheffield and WebElements Ltd, UK. Retrieved 4 March 2013.
8. R. P. Bush (1991). "Recovery of Platinum Group Metals from High Level Radioactive Waste" (PDF). Platinum Metals Review. 35 (4): 202–208.

• Isotope masses from:
  • 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
• 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. Lay summary.
• 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.