Isotopes of lead

Lead (Pb) has four 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. These series represent the decay chain products of long-lived primordial U-238, U-235, and Th-232, respectively. However, each of them 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).

The longest-lived radioisotopes are ²⁰⁵Pb with a half-life of ~15.3 million years and ²⁰²Pb with a half-life of ~53,000 years. Of naturally-occurring radioisotopes, the shortest half-life is 22.20 years for ²¹⁰Pb, which is useful for studying the sedimentation chronology of environmental samples on time scales shorter than 100 years.^[1]

The relative atomic mass (abundance-weighted average of the stable isotopes) is 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 1.9×10¹⁹ years). A total of 38 Pb isotopes are now known, including very unstable synthetic species.

In its fully ionized state the isotope ²⁰⁵Pb also becomes stable.^[2]

Lead-206

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 more rare ²⁰⁶Tl (radium E^II) by beta decay.

Lead 207, 208, and 204

²⁰⁷Pb is the end of the Actinium series from ²³⁵U.

²⁰⁸Pb is the end of the Thorium series from ²³²Th. It is notable for its unusually low neutron capture cross section (even lower than that of deuterium in the thermal spectrum), making it of interest for lead-cooled fast reactors. 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.^[3] It is notable as the heaviest known stable isotope of any element.

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). Any excess lead 206, 207, and 208 is thus assumed to be radiogenic in origin, allowing various uranium and thorium dating schemes to be used to estimate the age of rocks (time since their formation).

Table

nuclide symbol	historic name	Z(p)	N(n)	isotopic mass (u)	half-life	decay mode(s)[4][n 1]	daughter isotope(s)[n 2]	nuclear spin	representative isotopic composition (mole fraction)	range of natural variation (mole fraction)
		excitation energy
^178Pb		82	96	178.003830(26)	0.23(15) ms			0+
^179Pb		82	97	179.00215(21)#	3# ms			5/2−#
^180Pb		82	98	179.997918(22)	4.5(11) ms			0+
^181Pb		82	99	180.99662(10)	45(20) ms	α (98%)	^177Hg	5/2−#
						β^+ (2%)	^181Tl
^182Pb		82	100	181.992672(15)	60(40) ms [55(+40−35) ms]	α (98%)	^178Hg	0+
						β^+ (2%)	^182Tl
^183Pb		82	101	182.99187(3)	535(30) ms	α (94%)	^179Hg	(3/2−)
						β^+ (6%)	^183Tl
^183mPb		94(8) keV			415(20) ms	α	^179Hg	(13/2+)
						β^+ (rare)	^183Tl
^184Pb		82	102	183.988142(15)	490(25) ms	α	^180Hg	0+
						β^+ (rare)	^184Tl
^185Pb		82	103	184.987610(17)	6.3(4) s	α	^181Hg	3/2−
						β^+ (rare)	^185Tl
^185mPb		60(40)# keV			4.07(15) s	α	^181Hg	13/2+
						β^+ (rare)	^185Tl
^186Pb		82	104	185.984239(12)	4.82(3) s	α (56%)	^182Hg	0+
						β^+ (44%)	^186Tl
^187Pb		82	105	186.983918(9)	15.2(3) s	β^+	^187Tl	(3/2−)
						α	^183Hg
^187mPb		11(11) keV			18.3(3) s	β^+ (98%)	^187Tl	(13/2+)
						α (2%)	^183Hg
^188Pb		82	106	187.980874(11)	25.5(1) s	β^+ (91.5%)	^188Tl	0+
						α (8.5%)	^184Hg
^188m1Pb		2578.2(7) keV			830(210) ns			(8−)
^188m2Pb		2800(50) keV			797(21) ns
^189Pb		82	107	188.98081(4)	51(3) s	β^+	^189Tl	(3/2−)
^189mPb		40(30)# keV			1# min	β^+ (99.6%)	^189Tl	(13/2+)
						α (.4%)	^185Hg
^190Pb		82	108	189.978082(13)	71(1) s	β^+ (99.1%)	^190Tl	0+
						α (.9%)	^186Hg
^190m1Pb		2614.8(8) keV			150 ns			(10)+
^190m2Pb		2618(20) keV			25 µs			(12+)
^190m3Pb		2658.2(8) keV			7.2(6) µs			(11)−
^191Pb		82	109	190.97827(4)	1.33(8) min	β^+ (99.987%)	^191Tl	(3/2−)
						α (.013%)	^187Hg
^191mPb		20(50) keV			2.18(8) min	β^+ (99.98%)	^191Tl	13/2(+)
						α (.02%)	^187Hg
^192Pb		82	110	191.975785(14)	3.5(1) min	β^+ (99.99%)	^192Tl	0+
						α (.0061%)	^188Hg
^192m1Pb		2581.1(1) keV			164(7) ns			(10)+
^192m2Pb		2625.1(11) keV			1.1(5) µs			(12+)
^192m3Pb		2743.5(4) keV			756(21) ns			(11)−
^193Pb		82	111	192.97617(5)	5# min	β^+	^193Tl	(3/2−)
^193m1Pb		130(80)# keV			5.8(2) min	β^+	^193Tl	13/2(+)
^193m2Pb		2612.5(5)+X keV			135(+25−15) ns			(33/2+)
^194Pb		82	112	193.974012(19)	12.0(5) min	β^+ (100%)	^194Tl	0+
						α (7.3×10^−6%)	^190Hg
^195Pb		82	113	194.974542(25)	~15 min	β^+	^195Tl	3/2#-
^195m1Pb		202.9(7) keV			15.0(12) min	β^+	^195Tl	13/2+
^195m2Pb		1759.0(7) keV			10.0(7) µs			21/2−
^196Pb		82	114	195.972774(15)	37(3) min	β^+	^196Tl	0+
						α (3×10^−5%)	^192Hg
^196m1Pb		1049.20(9) keV			<100 ns			2+
^196m2Pb		1738.27(12) keV			<1 µs			4+
^196m3Pb		1797.51(14) keV			140(14) ns			5−
^196m4Pb		2693.5(5) keV			270(4) ns			(12+)
^197Pb		82	115	196.973431(6)	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
						α (3×10^−4%)	^193Hg
^197m2Pb		1914.10(25) keV			1.15(20) µs			21/2−
^198Pb		82	116	197.972034(16)	2.4(1) h	β^+	^198Tl	0+
^198m1Pb		2141.4(4) keV			4.19(10) µs			(7)−
^198m2Pb		2231.4(5) keV			137(10) ns			(9)−
^198m3Pb		2820.5(7) keV			212(4) ns			(12)+
^199Pb		82	117	198.972917(28)	90(10) min	β^+	^199Tl	3/2−
^199m1Pb		429.5(27) keV			12.2(3) min	IT (93%)	^199Pb	(13/2+)
						β^+ (7%)	^199Tl
^199m2Pb		2563.8(27) keV			10.1(2) µs			(29/2−)
^200Pb		82	118	199.971827(12)	21.5(4) h	β^+	^200Tl	0+
^201Pb		82	119	200.972885(24)	9.33(3) h	EC (99%)	^201Pb	5/2−
						β^+ (1%)	^201Tl
^201m1Pb		629.14(17) keV			61(2) s			13/2+
^201m2Pb		2718.5+X keV			508(5) ns			(29/2−)
^202Pb		82	120	201.972159(9)	52.5(28)×10^3 y	EC (99%)	^202Tl	0+
						α (1%)	^198Hg
^202m1Pb		2169.83(7) keV			3.53(1) h	IT (90.5%)	^202Pb	9−
						EC (9.5%)	^202Tl
^202m2Pb		4142.9(11) keV			110(5) ns			(16+)
^202m3Pb		5345.9(13) keV			107(5) ns			(19−)
^203Pb		82	121	202.973391(7)	51.873(9) h	EC	^203Tl	5/2−
^203m1Pb		825.20(9) keV			6.21(8) s	IT	^203Pb	13/2+
^203m2Pb		2949.47(22) keV			480(7) ms			29/2−
^203m3Pb		2923.4+X keV			122(4) ns			(25/2−)
^204Pb[n 3]		82	122	203.9730436(13)	Observationally Stable[n 4]			0+	0.014(1)	0.0104–0.0165
^204m1Pb		1274.00(4) keV			265(10) ns			4+
^204m2Pb		2185.79(5) keV			67.2(3) min			9−
^204m3Pb		2264.33(4) keV			0.45(+10−3) µs			7−
^205Pb		82	123	204.9744818(13)	15.3(7)×10^6 y	EC	^205Tl	5/2−
^205m1Pb		2.329(7) keV			24.2(4) µs			1/2−
^205m2Pb		1013.839(13) keV			5.55(2) ms			13/2+
^205m3Pb		3195.7(5) keV			217(5) ns			25/2−
^206Pb[n 3][n 5]	Radium G	82	124	205.9744653(13)	Observationally Stable[n 6]			0+	0.241(1)	0.2084–0.2748
^206m1Pb		2200.14(4) keV			125(2) µs			7−
^206m2Pb		4027.3(7) keV			202(3) ns			12+
^207Pb[n 3][n 7]	Actinium D	82	125	206.9758969(13)	Observationally Stable[n 8]			1/2−	0.221(1)	0.1762–0.2365
^207mPb		1633.368(5) keV			806(6) ms	IT	^207Pb	13/2+
^208Pb[n 9]	Thorium D	82	126	207.9766521(13)	Observationally Stable[n 10]			0+	0.524(1)	0.5128–0.5621
^208mPb		4895(2) keV			500(10) ns			10+
^209Pb		82	127	208.9810901(19)	3.253(14) h	β^−	^209Bi	9/2+	Trace[n 11]
^210Pb	Radium D Radiolead Radio-lead	82	128	209.9841885(16)	22.20(22) y	β^− (100%)	^210Bi	0+	Trace[n 12]
						α (1.9×10^−6%)	^206Hg
^210mPb		1278(5) keV			201(17) ns			8+
^211Pb	Actinium B	82	129	210.9887370(29)	36.1(2) min	β^−	^211Bi	9/2+	Trace[n 13]
^212Pb	Thorium B	82	130	211.9918975(24)	10.64(1) h	β^−	^212Bi	0+	Trace[n 14]
^212mPb		1335(10) keV			5(1) µs			(8+)
^213Pb		82	131	212.996581(8)	10.2(3) min	β^−	^213Bi	(9/2+)
^214Pb	Radium B	82	132	213.9998054(26)	26.8(9) min	β^−	^214Bi	0+	Trace[n 12]
^215Pb		82	133	215.00481(44)#	36(1) s			5/2+#

1. Abbreviations:
   EC: Electron capture
   IT: Isomeric transition
2. Bold for stable isotopes, bold italics for nearly-stable isotopes (half-life longer than the age of the universe)
3. Used in lead-lead dating
4. Believed to undergo α decay to ²⁰⁰Hg with a half-life over 140×10¹⁵ years
5. Final decay product of 4n+2 decay chain (the Radium or Uranium series)
6. Believed to undergo α decay to ²⁰²Hg
7. Final decay product of 4n+3 decay chain (the Actinium series)
8. Believed to undergo α decay to ²⁰³Hg
9. Final decay product of 4n decay chain (the Thorium series)
10. Heaviest observationally stable nuclide, believed to undergo α decay to ²⁰⁴Hg with a half-life over 2×10¹⁹ years
11. Cluster decay product of ²²³Ra, which occurs in the decay chain of ²³⁵U
12. Intermediate decay product of ²³⁸U
13. Intermediate decay product of ²³⁵U
14. Intermediate decay product of ²³²Th

Notes

• Evaluated isotopic composition is for most but not all commercial samples.
• The precision of the isotope abundances and atomic mass is limited through variations. The given ranges should be applicable to any normal terrestrial material.
• Geologically exceptional samples are known in which the isotopic composition lies outside the reported range. The uncertainty in the atomic mass may exceed the stated value for such specimens.
• Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
• Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC, which use expanded uncertainties.

References

1. Determining the Ages of Recent Sediments Using Measurements of Trace Radioactivity H.W. Jeter, Terra et Aqua, 78, 21-28 (2000)
2. Takahashi, K; Boyd, R. N.; Mathews, G. J.; Yokoi, K. (October 1987). "Bound-state beta decay of highly ionized atoms" (PDF). Physical Review C (New York, NY: American Institute of Physics for the American Physical Society) 36 (4). ISSN 0556-2813. OCLC 1639677. Retrieved 2013-08-27.
3. 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.
4. "Universal Nuclide Chart". nucleonica. Retrieved 2013-08-28. (registration required (help)).

• Isotope masses from:
  • G. Audi; A. H. Wapstra; C. Thibault; J. Blachot; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). 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:
  • J. R. de Laeter; J. K. Böhlke; P. De Bièvre; H. Hidaka; H. S. Peiser; K. J. R. Rosman; P. D. P. Taylor (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry 75 (6): 683–800. doi:10.1351/pac200375060683.
  • M. E. Wieser (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. See editing notes on this article's talk page.
  • G. Audi; A. H. Wapstra; C. Thibault; J. Blachot; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). Nuclear Physics A 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001.
  • National Nuclear Data Center. "NuDat 2.1 database". Brookhaven National Laboratory. Retrieved September 2005.
  • N. E. Holden (2004). "Table of the Isotopes". In D. R. Lide. CRC Handbook of Chemistry and Physics (85th ed.). CRC Press. Section 11. ISBN 978-0-8493-0485-9.