Isotopes of lead

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Lead (Pb) has four stable isotopes: 204Pb, 206Pb, 207Pb, 208Pb. Lead-204 is entirely a primordial nuclide and none of it is radiogenic. The isotopes lead-206, lead-207, and lead-208 represent the ends of decay chains called the uranium series (or radium series), the thorium series, and the actinium series respectively. These series represent the decay chain products of long-lived primoridal U-238, Th-232, and U-235 respectively. However, each of them also occurs, to some extent, as primordial isotopes which 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. The standard atomic mass (abundance-weighted average of the stable isotopes) is 207.2(1) u. It is the element with the heaviest stable isotope. (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.

Contents

[edit] Lead-206

See 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 more rare 206Tl (radium EII) by beta decay.


Lighter:
Lead-205
Isotopes of lead is an
isotope of lead
Heavier:
Lead-206
Decay product of:
Polonium-210 (α)
Thallium-206 (β-)
Decay chain
of Isotopes of lead
Decays to:
(stable)

[edit] 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.

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).

[edit] Historical names

Isotopes of lead occurring within the radioactive disintegration chains of actinium, radium, and thorium were historically known as:

[edit] Table

nuclide
symbol
Z(p) N(n)  
isotopic mass (u)
 
half-life 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 5/2-#
182Pb 82 100 181.992672(15) 60(40) ms [55(+40-35) ms] 0+
183Pb 82 101 182.99187(3) 535(30) ms (3/2-)
183mPb 94(8) keV 415(20) ms (13/2+)
184Pb 82 102 183.988142(15) 490(25) ms 0+
185Pb 82 103 184.987610(17) 6.3(4) s 3/2-
185mPb 60(40)# keV 4.07(15) s 13/2+
186Pb 82 104 185.984239(12) 4.82(3) s 0+
187Pb 82 105 186.983918(9) 15.2(3) s (3/2-)
187mPb 11(11) keV 18.3(3) s (13/2+)
188Pb 82 106 187.980874(11) 25.5(1) s 0+
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 (3/2-)
189mPb 40(30)# keV 1# min (13/2+)
190Pb 82 108 189.978082(13) 71(1) s 0+
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 (3/2-)
191mPb 20(50) keV 2.18(8) min 13/2(+)
192Pb 82 110 191.975785(14) 3.5(1) min 0+
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 (3/2-)
193m1Pb 130(80)# keV 5.8(2) min 13/2(+)
193m2Pb 2612.5(5)+X keV 135(+25-15) ns (33/2+)
194Pb 82 112 193.974012(19) 12.0(5) min 0+
195Pb 82 113 194.974542(25) ~15 min 3/2#-
195m1Pb 202.9(7) keV 15.0(12) min 13/2+
195m2Pb 1759.0(7) keV 10.0(7) µs 21/2-
196Pb 82 114 195.972774(15) 37(3) min 0+
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 3/2-
197m1Pb 319.31(11) keV 42.9(9) min 13/2+
197m2Pb 1914.10(25) keV 1.15(20) µs 21/2-
198Pb 82 116 197.972034(16) 2.4(1) h 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 3/2-
199m1Pb 429.5(27) keV 12.2(3) min (13/2+)
199m2Pb 2563.8(27) keV 10.1(2) µs (29/2-)
200Pb 82 118 199.971827(12) 21.5(4) h 0+
201Pb 82 119 200.972885(24) 9.33(3) h 5/2-
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)E+3 a 0+
202m1Pb 2169.83(7) keV 3.53(1) h 9-
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 5/2-
203m1Pb 825.20(9) keV 6.21(8) s 13/2+
203m2Pb 2949.47(22) keV 480(7) ms 29/2-
203m3Pb 2923.4+X keV 122(4) ns (25/2-)
204Pb 82 122 203.9730436(13) STABLE [>140E+15 a] 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)E+6 a 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 82 124 205.9744653(13) STABLE 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 82 125 206.9758969(13) STABLE 1/2- 0.221(1) 0.1762-0.2365
207mPb 1633.368(5) keV 806(6) ms 13/2+
208Pb 82 126 207.9766521(13) STABLE [>2E+19 a] 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 9/2+
210Pb 82 128 209.9841885(16) 22.20(22) a 0+
210mPb 1278(5) keV 201(17) ns 8+
211Pb 82 129 210.9887370(29) 36.1(2) min 9/2+
212Pb 82 130 211.9918975(24) 10.64(1) h 0+
212mPb 1335(10) keV 5(1) µs (8+)
213Pb 82 131 212.996581(8) 10.2(3) min (9/2+)
214Pb 82 132 213.9998054(26) 26.8(9) min 0+
215Pb 82 133 215.00481(44)# 36(1) s 5/2+#

[edit] Notes

[edit] References


Isotopes of thallium Isotopes of lead Isotopes of bismuth
Index to isotope pages · Table of nuclides
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