Isotopes of thallium

Thallium (₈₁Tl) has 41 isotopes with atomic masses that range from 176 to 216. ²⁰³Tl and ²⁰⁵Tl are the only stable isotopes and ²⁰⁴Tl is the most stable radioisotope with a half-life of 3.78 years. ²⁰⁷Tl, with a half-life of 4.77 minutes, has the longest half-life of naturally occurring Tl radioisotopes. All isotopes of thallium are either radioactive or observationally stable, meaning that they are predicted to be radioactive but no actual decay has been observed.

Isotopes of thallium (₈₁Tl)

Main isotopes[1] Decay abun­dance half-life (t1/2) mode pro­duct 201Tl synth 3.0421 d ε 201Hg 203Tl 29.5% stable 204Tl synth 3.78 y β− 204Pb ε 204Hg 205Tl 70.5% stable
Standard atomic weight Ar°(Tl)
	[204.382, 204.385][2] 204.38±0.01 (abridged)[3]
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Thallium-202 (half-life 12.23 days) can be made in a cyclotron^[4] while thallium-204 (half-life 3.78 years) is made by the neutron activation of stable thallium in a nuclear reactor.^[5]

In the fully ionized state, the isotope ²⁰⁵Tl⁸¹⁺ becomes beta-radioactive, undergoing bound-state β⁻ decay to ²⁰⁵Pb⁸¹⁺ with a half-life of 291+33
−27 days,^[6][7] but ²⁰³Tl remains stable.

²⁰⁵Tl is the decay product of bismuth-209, an isotope that was once thought to be stable but is now known to undergo alpha decay with an extremely long half-life of 2.01×10¹⁹ y.^{[8] 205}Tl is at the end of the neptunium series decay chain.

The neptunium series decay chain, which ends at ²⁰⁵Tl.

List of isotopes

Nuclide[9] [n 1]	Historic name	Z	N	Isotopic mass (Da)[10] [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
176Tl[11]		81	95	176.00059(21)#	2.4+1.6 −0.7 ms	p (~63%)	175Hg	(3−, 4−, 5−)
						α (~37%)	172Au
176mTl		~671 keV			290+200 −80 μs	p (~50%)	175Hg
						α (~50%)	172mAu
177Tl[12]		81	96	176.996427(27)	18(5) ms	α (73%)	173Au	(1/2+)
						p (27%)	176Hg
177mTl		807(18) keV			230(40) μs	p (51%)	176Hg	(11/2−)
						α (49%)	173Au
178Tl[13]		81	97	177.99490(12)#	255(9) ms	α (62%)	174Au	(4-,5-)
						β+ (38%)	178Hg
						β+, SF (0.15%)	(various)
179Tl[14]		81	98	178.99109(5)	437(9) ms	α (60%)	175Au	(1/2+)
						β+ (40%)	179Hg
179m1Tl		825(10)# keV			1.41(2) ms	α	175Au	(11/2−)
						IT (rare)	179Tl
						β+ (rare)	179Hg
179m2Tl		904.5(9) keV			119(14) ns	IT	179Tl	(9/2−)
180Tl[15]		81	99	179.98991(13)#	1.09(1) s	β+ (93%)	180Hg	4-#
						α (7%)	176Au
						β+, SF (0.0032%)	100Ru, 80Kr[16]
181Tl[17]		81	100	180.986257(10)	2.9(1) s	β+ (91.4%)	181Hg	1/2+#
						α (8.6%)	177Au
181mTl		834.9(4) keV			1.40(3) ms	IT (99.60%)	181Tl	(9/2−)
						α (0.40%)	177Au
182Tl		81	101	181.98567(8)	2.0(3) s	β+ (96%)	182Hg	2−#
						α (4%)	178Au
182m1Tl		100(100)# keV			2.9(5) s	α	178Au	(7+)
						β+ (rare)	182Hg
182m2Tl		600(140)# keV						10−
183Tl		81	102	182.982193(10)	6.9(7) s	β+ (98%)	183Hg	1/2+#
						α (2%)	179Au
183m1Tl		630(17) keV			53.3(3) ms	IT (99.99%)	183Tl	9/2−#
						α (.01%)	179Au
183m2Tl		976.8(3) keV			1.48(10) μs			(13/2+)
184Tl		81	103	183.98187(5)	9.7(6) s	β+	184Hg	2−#
184m1Tl		100(100)# keV			10# s	β+ (97.9%)	184Hg	7+#
						α (2.1%)	180Au
184m2Tl		500(140)# keV			47.1 ms	IT (99.911%)		(10−)
						α (.089%)	180Au
185Tl		81	104	184.97879(6)	19.5(5) s	α	181Au	1/2+#
						β+	185Hg
185mTl		452.8(20) keV			1.93(8) s	IT (99.99%)	185Tl	9/2−#
						α (.01%)	181Au
						β+	185Hg
186Tl		81	105	185.97833(20)	40# s	β+	186Hg	(2−)
						α (.006%)	182Au
186m1Tl		320(180) keV			27.5(10) s	β+	186Hg	(7+)
186m2Tl		690(180) keV			2.9(2) s			(10−)
187Tl		81	106	186.975906(9)	~51 s	β+	187Hg	(1/2+)
						α (rare)	183Au
187mTl		335(3) keV			15.60(12) s	α	183Au	(9/2−)
						IT	187Tl
						β+	187Hg
188Tl		81	107	187.97601(4)	71(2) s	β+	188Hg	(2−)
188m1Tl		40(30) keV			71(1) s	β+	188Hg	(7+)
188m2Tl		310(30) keV			41(4) ms			(9−)
189Tl		81	108	188.973588(12)	2.3(2) min	β+	189Hg	(1/2+)
189mTl		257.6(13) keV			1.4(1) min	β+ (96%)	189Hg	(9/2−)
						IT (4%)	189Tl
190Tl		81	109	189.97388(5)	2.6(3) min	β+	190Hg	2(−)
190m1Tl		130(90)# keV			3.7(3) min	β+	190Hg	7(+#)
190m2Tl		290(70)# keV			750(40) μs			(8−)
190m3Tl		410(70)# keV			>1 μs			9−
191Tl		81	110	190.971786(8)	20# min	β+	191Hg	(1/2+)
191mTl		297(7) keV			5.22(16) min	β+	191Hg	9/2(−)
192Tl		81	111	191.97223(3)	9.6(4) min	β+	192Hg	(2−)
192m1Tl		160(50) keV			10.8(2) min	β+	192Hg	(7+)
192m2Tl		407(54) keV			296(5) ns			(8−)
193Tl		81	112	192.97067(12)	21.6(8) min	β+	193Hg	1/2(+#)
193mTl		369(4) keV			2.11(15) min	IT (75%)	193Tl	9/2−
						β+ (25%)	193Hg
194Tl		81	113	193.97120(15)	33.0(5) min	β+	194Hg	2−
						α (10−7%)	190Au
194mTl		300(200)# keV			32.8(2) min	β+	194Hg	(7+)
195Tl		81	114	194.969774(15)	1.16(5) h	β+	195Hg	1/2+
195mTl		482.63(17) keV			3.6(4) s	IT	195Tl	9/2−
196Tl		81	115	195.970481(13)	1.84(3) h	β+	196Hg	2−
196mTl		394.2(5) keV			1.41(2) h	β+ (95.5%)	196Hg	(7+)
						IT (4.5%)	196Tl
197Tl		81	116	196.969575(18)	2.84(4) h	β+	197Hg	1/2+
197mTl		608.22(8) keV			540(10) ms	IT	197Tl	9/2−
198Tl		81	117	197.97048(9)	5.3(5) h	β+	198Hg	2−
198m1Tl		543.5(4) keV			1.87(3) h	β+ (54%)	198Hg	7+
						IT (46%)	198Tl
198m2Tl		687.2(5) keV			150(40) ns			(5+)
198m3Tl		742.3(4) keV			32.1(10) ms			(10−)#
199Tl		81	118	198.96988(3)	7.42(8) h	β+	199Hg	1/2+
199mTl		749.7(3) keV			28.4(2) ms	IT	199Tl	9/2−
200Tl		81	119	199.970963(6)	26.1(1) h	β+	200Hg	2−
200m1Tl		753.6(2) keV			34.3(10) ms	IT	200Tl	7+
200m2Tl		762.0(2) keV			0.33(5) μs			5+
201Tl[n 8]		81	120	200.970819(16)	72.912(17) h	EC	201Hg	1/2+
201mTl		919.50(9) keV			2.035(7) ms	IT	201Tl	(9/2−)
202Tl		81	121	201.972106(16)	12.23(2) d	β+	202Hg	2−
202mTl		950.19(10) keV			572(7) μs			7+
203Tl		81	122	202.9723442(14)	Observationally Stable[n 9]			1/2+	0.2952(1)	0.29494–0.29528
203mTl		3400(300) keV			7.7(5) μs			(25/2+)
204Tl		81	123	203.9738635(13)	3.78(2) y	β− (97.1%)	204Pb	2−
						EC (2.9%)	204Hg
204m1Tl		1104.0(4) keV			63(2) μs			(7)+
204m2Tl		2500(500) keV			2.6(2) μs			(12−)
204m3Tl		3500(500) keV			1.6(2) μs			(20+)
205Tl[n 10]		81	124	204.9744275(14)	Observationally Stable[n 11][n 12]			1/2+	0.7048(1)	0.70472–0.70506
205m1Tl		3290.63(17) keV			2.6(2) μs			25/2+
205m2Tl		4835.6(15) keV			235(10) ns			(35/2–)
206Tl	Radium E	81	125	205.9761103(15)	4.200(17) min	β−	206Pb	0−	Trace[n 13]
206mTl		2643.11(19) keV			3.74(3) min	IT	206Tl	(12–)
207Tl	Actinium C	81	126	206.977419(6)	4.77(2) min	β−	207Pb	1/2+	Trace[n 14]
207mTl		1348.1(3) keV			1.33(11) s	IT (99.9%)	207Tl	11/2–
						β− (.1%)	207Pb
208Tl	Thorium C"	81	127	207.9820187(21)	3.053(4) min	β−	208Pb	5+	Trace[n 15]
209Tl		81	128	208.985359(8)	2.161(7) min	β−	209Pb	1/2+	Trace[n 16]
210Tl	Radium C″	81	129	209.990074(12)	1.30(3) min	β− (99.991%)	210Pb	(5+)#	Trace[n 13]
						β−, n (.009%)	209Pb
211Tl		81	130	210.993480(50)	80(16) s	β− (97.8%)	211Pb	1/2+
						β−, n (2.2%)	210Pb
212Tl		81	131	211.998340(220)#	31(8) s	β− (98.2%)	212Pb	(5+)
						β−, n (1.8%)	211Pb
213Tl		81	132	213.001915(29)	24(4) s	β− (92.4%)	213Pb	1/2+
						β−, n (7.6%)	212Pb
214Tl		81	133	214.006940(210)#	11(2) s	β− (66%)	214Pb	5+#
						β−, n (34%)	213Pb
215Tl		81	134	215.010640(320)#	10(4) s	β− (95.4%)	215Pb	1/2+#
						β−, n (4.6%)	214Pb
216Tl		81	135	216.015800(320)#	6(3) s	β−	216Pb	5+#
						β−, n (<11.5%)	215Pb
This table header & footer: view

1. ^mTl – 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
   n:	Neutron emission
   p:	Proton emission

6. Bold symbol as daughter – Daughter product is stable.
7. ( ) spin value – Indicates spin with weak assignment arguments.
8. Main isotope used in scintigraphy
9. Believed to undergo α decay to ¹⁹⁹Au
10. Final decay product of 4n+1 decay chain (the Neptunium series)
11. Believed to undergo α decay to ²⁰¹Au
12. Can undergo bound-state β⁻ decay to ²⁰⁵Pb⁸¹⁺ with a half-life of 291+33
    −27 days when fully ionized^[7]
13. Intermediate decay product of ²³⁸U
14. Intermediate decay product of ²³⁵U
15. Intermediate decay product of ²³²Th
16. Intermediate decay product of ²³⁷Np

Thallium-201

Thallium-201 (²⁰¹Tl) is a synthetic radioisotope of thallium. It has a half-life of 73 hours and decays by electron capture, emitting X-rays (~70–80 keV), and photons of 135 and 167 keV in 10% total abundance.^[18] Thallium-201 is synthesized by the neutron activation of stable thallium in a nuclear reactor,^[18][19] or by the ²⁰³Tl(p, 3n)²⁰¹Pb nuclear reaction in cyclotrons, as ²⁰¹Pb naturally decays to ²⁰¹Tl afterwards.^[20] It is a radiopharmaceutical, as it has good imaging characteristics without excessive patient radiation dose. It is the most popular isotope used for thallium nuclear cardiac stress tests.^[21]

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: Thallium". CIAAW. 2009.
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. "Thallium Research". doe.gov. Department of Energy. Archived from the original on 2006-12-09. Retrieved 23 March 2018.
5. Manual for reactor produced radioisotopes from the International Atomic Energy Agency
6. "Bound-state beta decay of highly ionized atoms" (PDF). Archived from the original (PDF) on October 29, 2013. Retrieved June 9, 2013.
7. M., Bai; K., Blaum; B., Boev; F., Bosch; C., Brandau; V., Cvetković; T., Dickel; I., Dillmann; D., Dmytriiev; T., Faestermann; O., Forstner; B., Franczak; H., Geissel; R., Gernhäuser; J., Glorius; C. J., Griffin; A., Gumberidze; E., Haettner; P.-M., Hillenbrand; P., Kienle; W., Korten; Ch., Kozhuharov; N., Kuzminchuk; K., Langanke; S., Litvinov; E., Menz; T., Morgenroth; C., Nociforo; F., Nolden; M. K., Pavićević; N., Petridis; U., Popp; S., Purushothaman; R., Reifarth; M. S., Sanjari; C., Scheidenberger; U., Spillmann; M., Steck; Th., Stöhlker; Y. K., Tanaka; M., Trassinelli; S., Trotsenko; L., Varga; M., Wang; H., Weick; P. J., Woods; T., Yamaguchi; Y. H., Zhang; J., Zhao; K., Zuber; et al. (E121 Collaboration and LOREX Collaboration) (2 December 2024). "Bound-State Beta Decay of ²⁰⁵Tl⁸¹⁺ Ions and the LOREX Project". Physical Review Letter. 133 (23). American Physical Society: 232701. doi:10.1103/PhysRevLett.133.232701.
8. Marcillac, P.; Coron, N.; Dambier, G.; et al. (2003). "Experimental detection of α-particles from the radioactive decay of natural bismuth". Nature. 422 (6934): 876–878. Bibcode:2003Natur.422..876D. doi:10.1038/nature01541. PMID 12712201. S2CID 4415582.
9. Half-life, decay mode, nuclear spin, and isotopic composition is sourced in:
   Audi, G.; Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S. (2017). "The NUBASE2016 evaluation of nuclear properties" (PDF). Chinese Physics C. 41 (3): 030001. Bibcode:2017ChPhC..41c0001A. doi:10.1088/1674-1137/41/3/030001.
10. Wang, M.; Audi, G.; Kondev, F. G.; Huang, W. J.; Naimi, S.; Xu, X. (2017). "The AME2016 atomic mass evaluation (II). Tables, graphs, and references" (PDF). Chinese Physics C. 41 (3): 030003-1–030003-442. doi:10.1088/1674-1137/41/3/030003.
11. Al-Aqeel, Muneerah Abdullah M. "Decay Spectroscopy of the Thallium Isotopes 176,177Tl". University of Liverpool. ProQuest 2447566201. Retrieved 21 June 2023.
12. Poli, G. L.; Davids, C. N.; Woods, P. J.; Seweryniak, D.; Batchelder, J. C.; Brown, L. T.; Bingham, C. R.; Carpenter, M. P.; Conticchio, L. F.; Davinson, T.; DeBoer, J.; Hamada, S.; Henderson, D. J.; Irvine, R. J.; Janssens, R. V. F.; Maier, H. J.; Müller, L.; Soramel, F.; Toth, K. S.; Walters, W. B.; Wauters, J. (1 June 1999). "Proton and $\ensuremath{\alpha}$ radioactivity below the $Z=82$ shell closure". Physical Review C. 59 (6): R2979–R2983. doi:10.1103/PhysRevC.59.R2979. Retrieved 21 June 2023.
13. Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (1 March 2021). "The NUBASE2020 evaluation of nuclear physics properties *". Chinese Physics C, High Energy Physics and Nuclear Physics. 45 (3): 030001. Bibcode:2021ChPhC..45c0001K. doi:10.1088/1674-1137/abddae. ISSN 1674-1137. OSTI 1774641.
14. Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (1 March 2021). "The NUBASE2020 evaluation of nuclear physics properties *". Chinese Physics C, High Energy Physics and Nuclear Physics. 45 (3): 030001. Bibcode:2021ChPhC..45c0001K. doi:10.1088/1674-1137/abddae. ISSN 1674-1137. OSTI 1774641.
15. Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (1 March 2021). "The NUBASE2020 evaluation of nuclear physics properties *". Chinese Physics C, High Energy Physics and Nuclear Physics. 45 (3): 030001. Bibcode:2021ChPhC..45c0001K. doi:10.1088/1674-1137/abddae. ISSN 1674-1137. OSTI 1774641.
16. Reich, E. S. (2010). "Mercury serves up a nuclear surprise: a new type of fission". Scientific American. Retrieved 12 May 2011.
17. Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (1 March 2021). "The NUBASE2020 evaluation of nuclear physics properties *". Chinese Physics C, High Energy Physics and Nuclear Physics. 45 (3): 030001. Bibcode:2021ChPhC..45c0001K. doi:10.1088/1674-1137/abddae. ISSN 1674-1137. OSTI 1774641.
18. 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
19. "Manual for reactor produced radioisotopes" (PDF). International Atomic Energy Agency. 2003. Archived (PDF) from the original on 2011-05-21. Retrieved 2010-05-13.
20. Cyclotron Produced Radionuclides: Principles and Practice (PDF). International Atomic Energy Agency. 2008. ISBN 9789201002082. Retrieved 2022-07-01.
21. Maddahi, Jamshid; Berman, Daniel (2001). "Detection, Evaluation, and Risk Stratification of Coronary Artery Disease by Thallium-201 Myocardial Perfusion Scintigraphy 155". Cardiac SPECT imaging (2nd ed.). Lippincott Williams & Wilkins. pp. 155–178. ISBN 978-0-7817-2007-6. Archived from the original on 2017-02-22. Retrieved 2016-09-26.

• 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.
• "News & Notices: Standard Atomic Weights Revised". International Union of Pure and Applied Chemistry. 19 October 2005.
• 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.