Isotopes of lead

Lead (₈₂Pb) has four observationally stable isotopes: ²⁰⁴Pb, ²⁰⁶Pb, ²⁰⁷Pb, ²⁰⁸Pb. Lead-204 is entirely a primordial nuclide and is not a radiogenic nuclide. The three isotopes lead-206, lead-207, and lead-208 represent the ends of three decay chains: the uranium series (or radium series), the actinium series, and the thorium series, respectively; a fourth decay chain, the neptunium series, terminates with the thallium isotope ²⁰⁵Tl. The three series terminating in lead represent the decay chain products of long-lived primordial ²³⁸U, ²³⁵U, and ²³²Th. Each isotope also occurs, to some extent, as primordial isotopes that were made in supernovae, rather than radiogenically as daughter products. The fixed ratio of lead-204 to the primordial amounts of the other lead isotopes may be used as the baseline to estimate the extra amounts of radiogenic lead present in rocks as a result of decay from uranium and thorium. (See lead–lead dating and uranium–lead dating.)

Isotopes of lead (₈₂Pb)

Main isotopes[1] Decay abun­dance half-life (t1/2) mode pro­duct 202Pb synth 5.25×104 y ε 202Tl 204Pb 1.40% stable 205Pb trace 1.73×107 y ε 205Tl 206Pb 24.1% stable 207Pb 22.1% stable 208Pb 52.4% stable 209Pb trace 3.253 h β− 209Bi 210Pb trace 22.20 y β− 210Bi α 206Hg 211Pb trace 36.1 min β− 211Bi 212Pb trace 10.64 h β− 212Bi 214Pb trace 26.8 min β− 214Bi Isotopic abundances vary greatly by sample[2]
Standard atomic weight Ar°(Pb)
	[206.14, 207.94][3] 207.2±1.1 (abridged)[4]
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The longest-lived radioisotopes are ²⁰⁵Pb with a half-life of 17.3 million years and ²⁰²Pb with a half-life of 52,500 years. A shorter-lived naturally occurring radioisotope, ²¹⁰Pb with a half-life of 22.2 years, is useful for studying the sedimentation chronology of environmental samples on time scales shorter than 100 years.^[5]

The relative abundances of the four stable isotopes are approximately 1.5%, 24%, 22%, and 52.5%, combining to give a standard atomic weight (abundance-weighted average of the stable isotopes) of 207.2(1). Lead is the element with the heaviest stable isotope, ²⁰⁸Pb. (The more massive ²⁰⁹Bi, long considered to be stable, actually has a half-life of 2.01×10¹⁹ years.) ²⁰⁸Pb is also a doubly magic isotope, as it has 82 protons and 126 neutrons.^[6] It is the heaviest doubly magic nuclide known. A total of 43 lead isotopes are now known, including very unstable synthetic species.

The four primordial isotopes of lead are all observationally stable, meaning that they are predicted to undergo radioactive decay but no decay has been observed yet. These four isotopes are predicted to undergo alpha decay and become isotopes of mercury which are themselves radioactive or observationally stable.

In its fully ionized state, the beta decay of isotope ²¹⁰Pb does not release a free electron; the generated electron is instead captured by the atom's empty orbitals.^[7]

List of isotopes

Nuclide [n 1]	Historic name	Z	N	Isotopic mass (Da)[8] [n 2][n 3]	Half-life[1]	Decay mode[1] [n 4]	Daughter isotope [n 5][n 6]	Spin and parity[1] [n 7][n 8]	Natural abundance (mole fraction)
		Excitation energy[n 8]							Normal proportion[1]	Range of variation
178Pb		82	96	178.003836(25)	250(80) μs	α	174Hg	0+
						β+?	178Tl
179Pb		82	97	179.002(87)	2.7(2) ms	α	175Hg	(9/2−)
180Pb		82	98	179.997916(13)	4.1(3) ms	α	176Hg	0+
181Pb		82	99	180.996661(91)	39.0(8) ms	α	177Hg	(9/2−)
						β+?	181Tl
182Pb		82	100	181.992674(13)	55(5) ms	α	178Hg	0+
						β+?	182Tl
183Pb		82	101	182.991863(31)	535(30) ms	α	179Hg	3/2−
						β+?	183Tl
183mPb		94(8) keV			415(20) ms	α	179Hg	13/2+
						β+?	183Tl
						IT?	183Pb
184Pb		82	102	183.988136(14)	490(25) ms	α (80%)	180Hg	0+
						β+? (20%)	184Tl
185Pb		82	103	184.987610(17)	6.3(4) s	β+ (66%)	185Tl	3/2−
						α (34%)	181Hg
185mPb[n 9]		70(50) keV			4.07(15) s	α (50%)	181Hg	13/2+
						β+? (50%)	185Tl
186Pb		82	104	185.984239(12)	4.82(3) s	β+? (60%)	186Tl	0+
						α (40%)	182Hg
187Pb		82	105	186.9839108(55)	15.2(3) s	β+ (90.5%)	187Tl	3/2−
						α (9.5%)	183Hg
187mPb[n 9]		19(10) keV			18.3(3) s	β+ (88%)	187Tl	13/2+
						α (12%)	183Hg
188Pb		82	106	187.980879(11)	25.1(1) s	β+ (91.5%)	188Tl	0+
						α (8.5%)	184Hg
188m1Pb		2577.2(4) keV			800(20) ns	IT	188Pb	8−
188m2Pb		2709.8(5) keV			94(12) ns	IT	188Pb	12+
188m3Pb		4783.4(7) keV			440(60) ns	IT	188Pb	(19−)
189Pb		82	107	188.980844(15)	39(8) s	β+ (99.58%)	189Tl	3/2−
						α (0.42%)	185Hg
189m1Pb		40(4) keV			50.5(21) s	β+ (99.6%)	189Tl	13/2+
						α (0.4%)	185Hg
						IT?	189Pb
189m2Pb		2475(4) keV			26(5) μs	IT	189Pb	31/2−
190Pb		82	108	189.978082(13)	71(1) s	β+ (99.60%)	190Tl	0+
						α (0.40%)	186Hg
190m1Pb		2614.8(8) keV			150(14) ns	IT	190Pb	10+
190m2Pb		2665(50)# keV			24.3(21) μs	IT	190Pb	(12+)
190m3Pb		2658.2(8) keV			7.7(3) μs	IT	190Pb	11−
191Pb		82	109	190.9782165(71)	1.33(8) min	β+ (99.49%)	191Tl	3/2−
						α (0.51%)	187Hg
191m1Pb		58(10) keV			2.18(8) min	β+ (99.98%)	191Tl	13/2+
						α (0.02%)	187Hg
191m2Pb		2659(10) keV			180(80) ns	IT	191Pb	33/2+
192Pb		82	110	191.9757896(61)	3.5(1) min	β+ (99.99%)	192Tl	0+
						α (0.0059%)	188Hg
192m1Pb		2581.1(1) keV			166(6) ns	IT	192Pb	10+
192m2Pb		2625.1(11) keV			1.09(4) μs	IT	192Pb	12+
192m3Pb		2743.5(4) keV			756(14) ns	IT	192Pb	11−
193Pb		82	111	192.976136(11)	4# min	β+?	193Tl	3/2−#
193m1Pb		93(12) keV			5.8(2) min	β+	193Tl	13/2+
193m2Pb		2707(13) keV			180(15) ns	IT	193Pb	33/2+
194Pb		82	112	193.974012(19)	10.7(6) min	β+	194Tl	0+
						α (7.3×10−6%)	190Hg
194m1Pb		2628.1(4) keV			370(13) ns	IT	194Pb	12+
194m2Pb		2933.0(4) keV			133(7) ns	IT	194Pb	11−
195Pb		82	113	194.9745162(55)	15.0(14) min	β+	195Tl	3/2-
195m1Pb		202.9(7) keV			15.0(12) min	β+	195Tl	13/2+
						IT?	195Pb
195m2Pb		1759.0(7) keV			10.0(7) μs	IT	195Pb	21/2−
195m3Pb		2901.7(8) keV			95(20) ns	IT	195Pb	33/2+
196Pb		82	114	195.9727876(83)	37(3) min	β+	196Tl	0+
						α (<3×10−5%)	192Hg
196m1Pb		1797.51(14) keV			140(14) ns	IT	196Pb	5−
196m2Pb		2694.6(3) keV			270(4) ns	IT	196Pb	12+
197Pb		82	115	196.9734347(52)	8.1(17) min	β+	197Tl	3/2−
197m1Pb		319.31(11) keV			42.9(9) min	β+ (81%)	197Tl	13/2+
						IT (19%)	197Pb
197m2Pb		1914.10(25) keV			1.15(20) μs	IT	197Pb	21/2−
198Pb		82	116	197.9720155(94)	2.4(1) h	β+	198Tl	0+
198m1Pb		2141.4(4) keV			4.12(7) μs	IT	198Pb	7−
198m2Pb		2231.4(5) keV			137(10) ns	IT	198Pb	9−
198m3Pb		2821.7(6) keV			212(4) ns	IT	198Pb	12+
199Pb		82	117	198.9729126(73)	90(10) min	β+	199Tl	3/2−
199m1Pb		429.5(27) keV			12.2(3) min	IT	199Pb	(13/2+)
						β+?	199Tl
199m2Pb		2563.8(27) keV			10.1(2) μs	IT	199Pb	(29/2−)
200Pb		82	118	199.971819(11)	21.5(4) h	EC	200Tl	0+
200m1Pb		2183.3(11) keV			456(6) ns	IT	200Pb	(9−)
200m2Pb		3005.8(12) keV			198(3) ns	IT	200Pb	12+)
201Pb		82	119	200.972870(15)	9.33(3) h	β+	201Tl	5/2−
201m1Pb		629.1(3) keV			60.8(18) s	IT	201Pb	13/2+
						β+?	201Tl
201m2Pb		2953(20) keV			508(3) ns	IT	201Pb	(29/2−)
202Pb		82	120	201.9721516(41)	5.25(28)×104 y	EC	202Tl	0+
202m1Pb		2169.85(8) keV			3.54(2) h	IT (90.5%)	202Pb	9−
						β+ (9.5%)	202Tl
202m2Pb		4140(50)# keV			100(3) ns	IT	202Pb	16+
202m3Pb		5300(50)# keV			108(3) ns	IT	202Pb	19−
203Pb		82	121	202.9733906(70)	51.924(15) h	EC	203Tl	5/2−
203m1Pb		825.2(3) keV			6.21(8) s	IT	203Pb	13/2+
203m2Pb		2949.2(4) keV			480(7) ms	IT	203Pb	29/2−
203m3Pb		2970(50)# keV			122(4) ns	IT	203Pb	25/2−#
204Pb[n 10]		82	122	203.9730435(12)	Observationally stable[n 11]			0+	0.014(6)	0.0000–0.0158[10]
204m1Pb		1274.13(5) keV			265(6) ns	IT	204Pb	4+
204m2Pb		2185.88(8) keV			66.93(10) min	IT	204Pb	9−
204m3Pb		2264.42(6) keV			490(70) ns	IT	204Pb	7−
205Pb		82	123	204.9744817(12)	17.0(9)×107 y	EC	205Tl	5/2−
205m1Pb		2.329(7) keV			24.2(4) μs	IT	205Pb	1/2−
205m2Pb		1013.85(3) keV			5.55(2) ms	IT	205Pb	13/2+
205m3Pb		3195.8(6) keV			217(5) ns	IT	205Pb	25/2−
206Pb[n 10][n 12]	Radium G[11]	82	124	205.9744652(12)	Observationally stable[n 13]			0+	0.241(30)	0.0190–0.8673[10]
206m1Pb		2200.16(4) keV			125(2) μs	IT	206Pb	7−
206m2Pb		4027.3(7) keV			202(3) ns	IT	206Pb	12+
207Pb[n 10][n 14]	Actinium D	82	125	206.9758968(12)	Observationally stable[n 15]			1/2−	0.221(50)	0.0035–0.2351[10]
207mPb		1633.356(4) keV			806(5) ms	IT	207Pb	13/2+
208Pb[n 16]	Thorium D	82	126	207.9766520(12)	Observationally stable[n 17]			0+	0.524(70)	0.0338–0.9775[10]
208mPb		4895.23(5) keV			535(35) ns	IT	208Pb	10+
209Pb		82	127	208.9810900(19)	3.235(5) h	β−	209Bi	9/2+	Trace[n 18]
210Pb	Radium D Radiolead Radio-lead	82	128	209.9841884(16)	22.20(22) y	β− (100%)	210Bi	0+	Trace[n 19]
						α (1.9×10−6%)	206Hg
210m1Pb		1194.61(18) keV			92(10) ns	IT	210Pb	6+
210m2Pb		1274.8(3) keV			201(17) ns	IT	210Pb	8+
211Pb	Actinium B	82	129	210.9887353(24)	36.1628(25) min	β−	211Bi	9/2+	Trace[n 20]
211mPb		1719(23) keV			159(28) ns	IT	211Pb	(27/2+)
212Pb	Thorium B	82	130	211.9918959(20)	10.627(6) h	β−	212Bi	0+	Trace[n 21]
212mPb		1335(2) keV			6.0(8) μs	IT	212Pb	8+#
213Pb		82	131	212.9965608(75)	10.2(3) min	β−	213Bi	(9/2+)	Trace[n 18]
213mPb		1331.0(17) keV			260(20) ns	IT	213Pb	(21/2+)
214Pb	Radium B	82	132	213.9998035(21)	27.06(7) min	β−	214Bi	0+	Trace[n 19]
214mPb		1420(20) keV			6.2(3) μs	IT	214Pb	8+#
215Pb		82	133	215.004662(57)	142(11) s	β−	215Bi	9/2+#
216Pb		82	134	216.00806(22)#	1.66(20) min	β−	216Bi	0+
216mPb		1514(20) keV			400(40) ns	IT	216Pb	8+#
217Pb		82	135	217.01316(32)#	19.9(53) s	β−	217Bi	9/2+#
218Pb		82	136	218.01678(32)#	14.8(68) s	β−	218Bi	0+
219Pb		82	137	219.02214(43)#	3# s [>300 ns]	β−?	219Bi	11/2+#
220Pb		82	138	220.02591(43)#	1# s [>300 ns]	β−?	220Bi	0+
This table header & footer: view

1. ^mPb – 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. Modes of decay:

   EC:	Electron capture
   IT:	Isomeric transition

5. Bold italics symbol as daughter – Daughter product is nearly stable.
6. Bold symbol as daughter – Daughter product is stable.
7. ( ) spin value – Indicates spin with weak assignment arguments.
8. # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
9. Order of ground state and isomer is uncertain.
10. Used in lead–lead dating
11. Believed to undergo α decay to ²⁰⁰Hg with a half-life over 1.4×10²⁰ years; the theoretical lifetime is around ~10^35–37 years.^[9]
12. Final decay product of 4n+2 decay chain (the Radium or Uranium series)
13. Believed to undergo α decay to ²⁰²Hg with a half-life over 2.5×10²¹ years; the theoretical lifetime is ~10^65–68 years.^[9]
14. Final decay product of 4n+3 decay chain (the Actinium series)
15. Believed to undergo α decay to ²⁰³Hg with a half-life over 1.9×10²¹ years; the theoretical lifetime is ~10^152–189 years.^[9]
16. Heaviest observationally stable nuclide; final decay product of 4n decay chain (the Thorium series)
17. Believed to undergo α decay to ²⁰⁴Hg with a half-life over 2.6×10²¹ years; the theoretical lifetime is ~10^124–132 years.^[9]
18. Intermediate decay product of ²³⁷Np
19. Intermediate decay product of ²³⁸U
20. Intermediate decay product of ²³⁵U
21. Intermediate decay product of ²³²Th

Lead-206

See also: Decay chain

²⁰⁶Pb is the final step in the decay chain of ²³⁸U, the "radium series" or "uranium series". In a closed system, over time, a given mass of ²³⁸U will decay in a sequence of steps culminating in ²⁰⁶Pb. The production of intermediate products eventually reaches an equilibrium (though this takes a long time, as the half-life of ²³⁴U is 245,500 years). Once this stabilized system is reached, the ratio of ²³⁸U to ²⁰⁶Pb will steadily decrease, while the ratios of the other intermediate products to each other remain constant.

Like most radioisotopes found in the radium series, ²⁰⁶Pb was initially named as a variation of radium, specifically radium G. It is the decay product of both ²¹⁰Po (historically called radium F) by alpha decay, and the much rarer ²⁰⁶Tl (radium E^II) by beta decay.

Lead-206 has been proposed for use in fast breeder nuclear fission reactor coolant over the use of natural lead mixture (which also includes other stable lead isotopes) as a mechanism to improve neutron economy and greatly suppress unwanted production of highly radioactive byproducts.^[12]

Lead-204, -207, and -208

²⁰⁴Pb is entirely primordial, and is thus useful for estimating the fraction of the other lead isotopes in a given sample that are also primordial, since the relative fractions of the various primordial lead isotopes is constant everywhere.^[13] Any excess lead-206, -207, and -208 is thus assumed to be radiogenic in origin,^[13] allowing various uranium and thorium dating schemes to be used to estimate the age of rocks (time since their formation) based on the relative abundance of lead-204 to other isotopes. ²⁰⁷Pb is the end of the actinium series from ²³⁵U.

²⁰⁸Pb is the end of the thorium series from ²³²Th. While it only makes up approximately half of the composition of lead in most places on Earth, it can be found naturally enriched up to around 90% in thorium ores.^{[14] 208}Pb is the heaviest known stable nuclide and also the heaviest known doubly magic nucleus, as Z = 82 and N = 126 correspond to closed nuclear shells.^[15] As a consequence of this particularly stable configuration, its neutron capture cross section is very low (even lower than that of deuterium in the thermal spectrum), making it of interest for lead-cooled fast reactors.

Lead-212

²¹²Pb-containing radiopharmaceuticals have been trialed as therapeutic agents for the experimental cancer treatment targeted alpha-particle therapy.^[16]

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. Meija et al. 2016.
3. "Standard Atomic Weights: Lead". CIAAW. 2020.
4. 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.
5. Jeter, Hewitt W. (March 2000). "Determining the Ages of Recent Sediments Using Measurements of Trace Radioactivity" (PDF). Terra et Aqua (78): 21–28. Archived from the original (PDF) on March 4, 2016. Retrieved October 23, 2019.
6. Blank, B.; Regan, P.H. (2000). "Magic and doubly-magic nuclei". Nuclear Physics News. 10 (4): 20–27. doi:10.1080/10506890109411553. S2CID 121966707.
7. Takahashi, K; Boyd, R. N.; Mathews, G. J.; Yokoi, K. (October 1987). "Bound-state beta decay of highly ionized atoms". Physical Review C. 36 (4): 1522–1528. Bibcode:1987PhRvC..36.1522T. doi:10.1103/PhysRevC.36.1522. ISSN 0556-2813. OCLC 1639677. PMID 9954244. Retrieved 2016-11-20. As can be seen in Table I (¹⁸⁷Re, ²¹⁰Pb, ²²⁷Ac, and ²⁴¹Pu), some continuum-state decays are energetically forbidden when the atom is fully ionized. This is because the atomic binding energies liberated by ionization, i.e., the total electron binding in the neutral atom, B_n, increases with Z. If [the decay energy] Q_n<B_n(Z+1)-B_n(Z), the continuum-state β decay is energetically forbidden.
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.
9. Beeman, J.W.; et al. (2013). "New experimental limits on the alpha decays of lead isotopes". European Physical Journal A. 49 (4): 50. arXiv:1212.2422. Bibcode:2013EPJA...49...50B. doi:10.1140/epja/i2013-13050-7. S2CID 254111888.
10. "Standard Atomic Weights: Lead". CIAAW. 2020.
11. Kuhn, W. (1929). "LXVIII. Scattering of thorium C" γ-radiation by radium G and ordinary lead". The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science. 8 (52): 628. doi:10.1080/14786441108564923.
12. Khorasanov, G. L.; Ivanov, A. P.; Blokhin, A. I. (2002). Polonium Issue in Fast Reactor Lead Coolants and One of the Ways of Its Solution. 10th International Conference on Nuclear Engineering. pp. 711–717. doi:10.1115/ICONE10-22330.
13. Woods, G.D. (November 2014). Lead isotope analysis: Removal of 204Hg isobaric interference from 204Pb using ICP-QQQ in MS/MS mode (PDF) (Report). Stockport, UK: Agilent Technologies.
14. A. Yu. Smirnov; V. D. Borisevich; A. Sulaberidze (July 2012). "Evaluation of specific cost of obtainment of lead-208 isotope by gas centrifuges using various raw materials". Theoretical Foundations of Chemical Engineering. 46 (4): 373–378. doi:10.1134/S0040579512040161. S2CID 98821122.
15. Blank, B.; Regan, P.H. (2000). "Magic and doubly-magic nuclei". Nuclear Physics News. 10 (4): 20–27. doi:10.1080/10506890109411553. S2CID 121966707.
16. Kokov, K.V.; Egorova, B.V.; German, M.N.; Klabukov, I.D.; Krasheninnikov, M.E.; Larkin-Kondrov, A.A.; Makoveeva, K.A.; Ovchinnikov, M.V.; Sidorova, M.V.; Chuvilin, D.Y. (2022). "212Pb: Production Approaches and Targeted Therapy Applications". Pharmaceutics. 14 (1): 189. doi:10.3390/pharmaceutics14010189. ISSN 1999-4923. PMC 8777968. PMID 35057083.

Sources

• Meija, Juris; et al. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure and Applied Chemistry. 88 (3): 265–291. doi:10.1515/pac-2015-0305.

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

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.