Isotopes of thallium

Isotopes of thallium (₈₁Tl)
ε + β+	204Hg
Standard atomic weight Ar°(Tl)
	[204.382, 204.385]; 204.38±0.01 (abridged);
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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.

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 ²⁰⁵Tl becomes beta-radioactive, decaying to ²⁰⁵Pb,^[6] 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.^[7] ²⁰⁵Tl is at the end of the neptunium series decay chain.

List of isotopes

Nuclide^[8] ^{[n 1]}	Historic name	Z	N	Isotopic mass (Da)^[9] ^{[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)
Nuclide^[8] ^{[n 1]}	Historic name	Excitation energy^{[n 4]}			Half-life ^{[n 4]}	Decay mode ^{[n 5]}	Daughter isotope ^{[n 6]}	Spin and parity ^{[n 7]}^{[n 4]}	Normal proportion	Range of variation
¹⁷⁶Tl^[10]		81	95	176.00059(21)#	2.4+1.6 −0.7 ms	p (~63%)	¹⁷⁵Hg	(3−, 4−, 5−)
¹⁷⁶Tl^[10]		81	95	176.00059(21)#	2.4+1.6 −0.7 ms	α (~37%)	¹⁷²Au	(3−, 4−, 5−)
^176mTl		~671 keV			290+200 −80 μs	p (~50%)	¹⁷⁵Hg
^176mTl		~671 keV			290+200 −80 μs	α (~50%)	^172mAu
¹⁷⁷Tl^[11]		81	96	176.996427(27)	18(5) ms	α (73%)	¹⁷³Au	(1/2+)
¹⁷⁷Tl^[11]		81	96	176.996427(27)	18(5) ms	p (27%)	¹⁷⁶Hg	(1/2+)
^177mTl		807(18) keV			230(40) μs	p (51%)	¹⁷⁶Hg	(11/2−)
^177mTl		807(18) keV			230(40) μs	α (49%)	¹⁷³Au	(11/2−)
¹⁷⁸Tl^[12]		81	97	177.99490(12)#	255(9) ms	α (62%)	¹⁷⁴Au	(4-,5-)
						β⁺ (38%)	¹⁷⁸Hg
						β⁺, SF (0.15%)	(various)
¹⁷⁹Tl^[13]		81	98	178.99109(5)	437(9) ms	α (60%)	¹⁷⁵Au	(1/2+)
¹⁷⁹Tl^[13]		81	98	178.99109(5)	437(9) ms	β⁺ (40%)	¹⁷⁹Hg	(1/2+)
^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^[14]		81	99	179.98991(13)#	1.09(1) s	β⁺ (93%)	¹⁸⁰Hg	4-#
						α (7%)	¹⁷⁶Au
						β⁺, SF (0.0032%)	¹⁰⁰Ru, ⁸⁰Kr^[15]
¹⁸¹Tl^[16]		81	100	180.986257(10)	2.9(1) s	β⁺ (91.4%)	¹⁸¹Hg	1/2+#
¹⁸¹Tl^[16]		81	100	180.986257(10)	2.9(1) s	α (8.6%)	¹⁷⁷Au	1/2+#
^181mTl		834.9(4) keV			1.40(3) ms	IT (99.60%)	¹⁸¹Tl	(9/2−)
^181mTl		834.9(4) keV			1.40(3) ms	α (0.40%)	¹⁷⁷Au	(9/2−)
¹⁸²Tl		81	101	181.98567(8)	2.0(3) s	β⁺ (96%)	¹⁸²Hg	2−#
¹⁸²Tl		81	101	181.98567(8)	2.0(3) s	α (4%)	¹⁷⁸Au	2−#
^182m1Tl		100(100)# keV			2.9(5) s	α	¹⁷⁸Au	(7+)
^182m1Tl		100(100)# keV			2.9(5) s	β⁺ (rare)	¹⁸²Hg	(7+)
^182m2Tl		600(140)# keV						10−
¹⁸³Tl		81	102	182.982193(10)	6.9(7) s	β⁺ (98%)	¹⁸³Hg	1/2+#
¹⁸³Tl		81	102	182.982193(10)	6.9(7) s	α (2%)	¹⁷⁹Au	1/2+#
^183m1Tl		630(17) keV			53.3(3) ms	IT (99.99%)	¹⁸³Tl	9/2−#
^183m1Tl		630(17) keV			53.3(3) ms	α (.01%)	¹⁷⁹Au	9/2−#
^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+#
^184m1Tl		100(100)# keV			10# s	α (2.1%)	¹⁸⁰Au	7+#
^184m2Tl		500(140)# keV			47.1 ms	IT (99.911%)		(10−)
^184m2Tl		500(140)# keV			47.1 ms	α (.089%)	¹⁸⁰Au	(10−)
¹⁸⁵Tl		81	104	184.97879(6)	19.5(5) s	α	¹⁸¹Au	1/2+#
¹⁸⁵Tl		81	104	184.97879(6)	19.5(5) s	β⁺	¹⁸⁵Hg	1/2+#
^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−)
¹⁸⁶Tl		81	105	185.97833(20)	40# s	α (.006%)	¹⁸²Au	(2−)
^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+)
¹⁸⁷Tl		81	106	186.975906(9)	~51 s	α (rare)	¹⁸³Au	(1/2+)
^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−)
^189mTl		257.6(13) keV			1.4(1) min	IT (4%)	¹⁸⁹Tl	(9/2−)
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−
^193mTl		369(4) keV			2.11(15) min	β⁺ (25%)	¹⁹³Hg	9/2−
¹⁹⁴Tl		81	113	193.97120(15)	33.0(5) min	β⁺	¹⁹⁴Hg	2−
¹⁹⁴Tl		81	113	193.97120(15)	33.0(5) min	α (10⁻⁷%)	¹⁹⁰Au	2−
^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+)
^196mTl		394.2(5) keV			1.41(2) h	IT (4.5%)	¹⁹⁶Tl	(7+)
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+
^198m1Tl		543.5(4) keV			1.87(3) h	IT (46%)	¹⁹⁸Tl	7+
^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−
²⁰⁴Tl		81	123	203.9738635(13)	3.78(2) y	EC (2.9%)	²⁰⁴Hg	2−
^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]}			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 12]}
^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 13]}
^207mTl		1348.1(3) keV			1.33(11) s	IT (99.9%)	²⁰⁷Tl	11/2–
^207mTl		1348.1(3) keV			1.33(11) s	β⁻ (.1%)	²⁰⁷Pb	11/2–
²⁰⁸Tl	Thorium C"	81	127	207.9820187(21)	3.053(4) min	β⁻	²⁰⁸Pb	5+	Trace^{[n 14]}
²⁰⁹Tl		81	128	208.985359(8)	2.161(7) min	β⁻	²⁰⁹Pb	1/2+	Trace^{[n 15]}
²¹⁰Tl	Radium C″	81	129	209.990074(12)	1.30(3) min	β⁻ (99.991%)	²¹⁰Pb	(5+)#	Trace^{[n 12]}
²¹⁰Tl	Radium C″	81	129	209.990074(12)	1.30(3) min	β⁻, n (.009%)	²⁰⁹Pb	(5+)#	Trace^{[n 12]}
²¹¹Tl		81	130	210.993480(50)	80(16) s	β⁻ (97.8%)	²¹¹Pb	1/2+
²¹¹Tl		81	130	210.993480(50)	80(16) s	β⁻, n (2.2%)	²¹⁰Pb	1/2+
²¹²Tl		81	131	211.998340(220)#	31(8) s	β⁻ (98.2%)	²¹²Pb	(5+)
²¹²Tl		81	131	211.998340(220)#	31(8) s	β⁻, n (1.8%)	²¹¹Pb	(5+)
²¹³Tl		81	132	213.001915(29)	24(4) s	β⁻ (92.4%)	²¹³Pb	1/2+
²¹³Tl		81	132	213.001915(29)	24(4) s	β⁻, n (7.6%)	²¹²Pb	1/2+
²¹⁴Tl		81	133	214.006940(210)#	11(2) s	β⁻ (66%)	²¹⁴Pb	5+#
²¹⁴Tl		81	133	214.006940(210)#	11(2) s	β⁻, n (34%)	²¹³Pb	5+#
²¹⁵Tl		81	134	215.010640(320)#	10(4) s	β⁻ (95.4%)	²¹⁵Pb	1/2+#
²¹⁵Tl		81	134	215.010640(320)#	10(4) s	β⁻, n (4.6%)	²¹⁴Pb	1/2+#
²¹⁶Tl		81	135	216.015800(320)#	6(3) s	β⁻	²¹⁶Pb	5+#
²¹⁶Tl		81	135	216.015800(320)#	6(3) s	β⁻, n (<11.5%)	²¹⁵Pb	5+#
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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.^[17] Thallium-201 is synthesized by the neutron activation of stable thallium in a nuclear reactor,^[17]^[18] or by the ²⁰³Tl(p, 3n)²⁰¹Pb nuclear reaction in cyclotrons, as ²⁰¹Pb naturally decays to ²⁰¹Tl afterwards.^[19] 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.^[20]

References

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.

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