Thallium Thallium is a chemical element with the symbol Tl and atomic number 81. It is a gray post-transition metal that is not found free in nature. When isolated, thallium resembles tin, but discolors when exposed to air. Chemists William Crookes an ...

(₈₁Tl) has 41

isotope Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers ( mass num ...

s with

atomic mass The atomic mass (''m''a or ''m'') is the mass of an atom. Although the SI unit of mass is the kilogram (symbol: kg), atomic mass is often expressed in the non-SI unit dalton (symbol: Da) – equivalently, unified atomic mass unit (u). 1&n ...

es that range from 176 to 216. ²⁰³Tl and ²⁰⁵Tl are the only stable isotopes and ²⁰⁴Tl is the most stable

radioisotope A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation; transferr ...

with a

half-life Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable ...

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 Stable nuclides are nuclides that are not radioactive and so (unlike radionuclides) do not spontaneously undergo radioactive decay. When such nuclides are referred to in relation to specific elements, they are usually termed stable isotopes. Th ...

, 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 while thallium-204 (half-life 3.78 years) is made by the

neutron activation Neutron activation is the process in which neutron radiation induces radioactivity in materials, and occurs when atomic nuclei capture free neutrons, becoming heavier and entering excited states. The excited nucleus decays immediately by emit ...

of stable thallium in a

nuclear reactor A nuclear reactor is a device used to initiate and control a fission nuclear chain reaction or nuclear fusion reactions. Nuclear reactors are used at nuclear power plants for electricity generation and in nuclear marine propulsion. Heat fr ...

. In the fully ionized state, the isotope ²⁰⁵Tl becomes beta-radioactive, decaying to ²⁰⁵Pb, but ²⁰³Tl remains stable. ²⁰⁵Tl is the decay product of

bismuth-209 Bismuth-209 (209Bi) is the isotope of bismuth with the longest known half-life of any radioisotope that undergoes α-decay (alpha decay). It has 83 protons and a magic number of 126 neutrons, and an atomic mass of 208.9803987 amu (atomic mass un ...

, an isotope that was once thought to be stable but is now known to undergo

alpha decay Alpha decay or α-decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (helium nucleus) and thereby transforms or 'decays' into a different atomic nucleus, with a mass number that is reduced by four and an at ...

with an extremely long half life of 2.01×10¹⁹ y. ²⁰⁵Tl is at the end of the

neptunium Neptunium is a chemical element with the symbol Np and atomic number 93. A radioactive actinide metal, neptunium is the first transuranic element. Its position in the periodic table just after uranium, named after the planet Uranus, led to it bein ...

series decay chain.

List of isotopes

, - , ¹⁷⁶Tl , , style="text-align:right" , 81 , style="text-align:right" , 95 , 176.00059(21)# , 5.2(+30−14) ms , , , (3−, 4−, 5−) , , , - , rowspan=2, ¹⁷⁷Tl , rowspan=2, , rowspan=2 style="text-align:right" , 81 , rowspan=2 style="text-align:right" , 96 , rowspan=2, 176.996427(27) , rowspan=2, 18(5) ms , p , ¹⁷⁶Hg , rowspan=2, (1/2+) , rowspan=2, , rowspan=2, , - , α (rare) , ¹⁷³Au , - , rowspan=2 style="text-indent:1em" , ^177mTl , rowspan=2, , rowspan=2 colspan="3" style="text-indent:2em" , 807(18) keV , rowspan=2, 230(40) μs , p , ¹⁷⁶Hg , rowspan=2, (11/2−) , rowspan=2, , rowspan=2, , - , α , ¹⁷³Au , - , rowspan=2, ¹⁷⁸Tl , rowspan=2, , rowspan=2 style="text-align:right" , 81 , rowspan=2 style="text-align:right" , 97 , rowspan=2, 177.99490(12)# , rowspan=2, 255(10) ms , α , ¹⁷⁴Au , rowspan=2, , rowspan=2, , rowspan=2, , - , p (rare) , ¹⁷⁷Hg , - , rowspan=2, ¹⁷⁹Tl , rowspan=2, , rowspan=2 style="text-align:right" , 81 , rowspan=2 style="text-align:right" , 98 , rowspan=2, 178.99109(5) , rowspan=2, 270(30) ms , α , ¹⁷⁵Au , rowspan=2, (1/2+) , rowspan=2, , rowspan=2, , - , p (rare) , ¹⁷⁸Hg , - , rowspan=2 style="text-indent:1em" , ^179mTl , rowspan=2, , rowspan=2 colspan="3" style="text-indent:2em" , 860(30)# keV , rowspan=2, 1.60(16) ms , α , ¹⁷⁵Au , rowspan=2, (9/2−) , rowspan=2, , rowspan=2, , - , IT (rare) , ¹⁷⁹Tl , - , rowspan=3, ¹⁸⁰Tl , rowspan=3, , rowspan=3 style="text-align:right" , 81 , rowspan=3 style="text-align:right" , 99 , rowspan=3, 179.98991(13)# , rowspan=3, 1.5(2) s , α (75%) , ¹⁷⁶Au , rowspan=3, , rowspan=3, , rowspan=3, , - , β⁺ (25%) , ¹⁸⁰Hg , - , EC, fission (10⁻⁴%) , ¹⁰⁰Ru, ⁸⁰Kr , - , rowspan=2, ¹⁸¹Tl , rowspan=2, , rowspan=2 style="text-align:right" , 81 , rowspan=2 style="text-align:right" , 100 , rowspan=2, 180.986257(10) , rowspan=2, 3.2(3) s , α , ¹⁷⁷Au , rowspan=2, 1/2+# , rowspan=2, , rowspan=2, , - , β⁺ , ¹⁸¹Hg , - , rowspan=2 style="text-indent:1em" , ^181mTl , rowspan=2, , rowspan=2 colspan="3" style="text-indent:2em" , 857(29) keV , rowspan=2, 1.7(4) ms , α , ¹⁷⁷Au , rowspan=2, 9/2−# , rowspan=2, , rowspan=2, , - , β⁺ , ¹⁸¹Hg , - , rowspan=2, ¹⁸²Tl , rowspan=2, , rowspan=2 style="text-align:right" , 81 , rowspan=2 style="text-align:right" , 101 , rowspan=2, 181.98567(8) , rowspan=2, 2.0(3) s , β⁺ (96%) , ¹⁸²Hg , rowspan=2, 2−# , rowspan=2, , rowspan=2, , - , α (4%) , ¹⁷⁸Au , - , rowspan=2 style="text-indent:1em" , ^182m1Tl , rowspan=2, , rowspan=2 colspan="3" style="text-indent:2em" , 100(100)# keV , rowspan=2, 2.9(5) s , α , ¹⁷⁸Au , rowspan=2, (7+) , rowspan=2, , rowspan=2, , - , β⁺ (rare) , ¹⁸²Hg , - , style="text-indent:1em" , ^182m2Tl , , colspan="3" style="text-indent:2em" , 600(140)# keV , , , , 10− , , , - , rowspan=2, ¹⁸³Tl , rowspan=2, , rowspan=2 style="text-align:right" , 81 , rowspan=2 style="text-align:right" , 102 , rowspan=2, 182.982193(10) , rowspan=2, 6.9(7) s , β⁺ (98%) , ¹⁸³Hg , rowspan=2, 1/2+# , rowspan=2, , rowspan=2, , - , α (2%) , ¹⁷⁹Au , - , rowspan=2 style="text-indent:1em" , ^183m1Tl , rowspan=2, , rowspan=2 colspan="3" style="text-indent:2em" , 630(17) keV , rowspan=2, 53.3(3) ms , IT (99.99%) , ¹⁸³Tl , rowspan=2, 9/2−# , rowspan=2, , rowspan=2, , - , α (.01%) , ¹⁷⁹Au , - , style="text-indent:1em" , ^183m2Tl , , colspan="3" style="text-indent:2em" , 976.8(3) keV , 1.48(10) μs , , , (13/2+) , , , - , ¹⁸⁴Tl , , style="text-align:right" , 81 , style="text-align:right" , 103 , 183.98187(5) , 9.7(6) s , β⁺ , ¹⁸⁴Hg , 2−# , , , - , rowspan=2 style="text-indent:1em" , ^184m1Tl , rowspan=2, , rowspan=2 colspan="3" style="text-indent:2em" , 100(100)# keV , rowspan=2, 10# s , β⁺ (97.9%) , ¹⁸⁴Hg , rowspan=2, 7+# , rowspan=2, , rowspan=2, , - , α (2.1%) , ¹⁸⁰Au , - , rowspan=2 style="text-indent:1em" , ^184m2Tl , rowspan=2, , rowspan=2 colspan="3" style="text-indent:2em" , 500(140)# keV , rowspan=2, 47.1 ms , IT (99.911%) , , rowspan=2, (10−) , rowspan=2, , rowspan=2, , - , α (.089%) , ¹⁸⁰Au , - , rowspan=2, ¹⁸⁵Tl , rowspan=2, , rowspan=2 style="text-align:right" , 81 , rowspan=2 style="text-align:right" , 104 , rowspan=2, 184.97879(6) , rowspan=2, 19.5(5) s , α , ¹⁸¹Au , rowspan=2, 1/2+# , rowspan=2, , rowspan=2, , - , β⁺ , ¹⁸⁵Hg , - , rowspan=3 style="text-indent:1em" , ^185mTl , rowspan=3, , rowspan=3 colspan="3" style="text-indent:2em" , 452.8(20) keV , rowspan=3, 1.93(8) s , IT (99.99%) , ¹⁸⁵Tl , rowspan=3, 9/2−# , rowspan=3, , rowspan=3, , - , α (.01%) , ¹⁸¹Au , - , β⁺ , ¹⁸⁵Hg , - , rowspan=2, ¹⁸⁶Tl , rowspan=2, , rowspan=2 style="text-align:right" , 81 , rowspan=2 style="text-align:right" , 105 , rowspan=2, 185.97833(20) , rowspan=2, 40# s , β⁺ , ¹⁸⁶Hg , rowspan=2, (2−) , rowspan=2, , rowspan=2, , - , α (.006%) , ¹⁸²Au , - , style="text-indent:1em" , ^186m1Tl , , colspan="3" style="text-indent:2em" , 320(180) keV , 27.5(10) s , β⁺ , ¹⁸⁶Hg , (7+) , , , - , style="text-indent:1em" , ^186m2Tl , , colspan="3" style="text-indent:2em" , 690(180) keV , 2.9(2) s , , , (10−) , , , - , rowspan=2, ¹⁸⁷Tl , rowspan=2, , rowspan=2 style="text-align:right" , 81 , rowspan=2 style="text-align:right" , 106 , rowspan=2, 186.975906(9) , rowspan=2, ~51 s , β⁺ , ¹⁸⁷Hg , rowspan=2, (1/2+) , rowspan=2, , rowspan=2, , - , α (rare) , ¹⁸³Au , - , rowspan=3 style="text-indent:1em" , ^187mTl , rowspan=3, , rowspan=3 colspan="3" style="text-indent:2em" , 335(3) keV , rowspan=3, 15.60(12) s , α , ¹⁸³Au , rowspan=3, (9/2−) , rowspan=3, , rowspan=3, , - , IT , ¹⁸⁷Tl , - , β⁺ , ¹⁸⁷Hg , - , ¹⁸⁸Tl , , style="text-align:right" , 81 , style="text-align:right" , 107 , 187.97601(4) , 71(2) s , β⁺ , ¹⁸⁸Hg , (2−) , , , - , style="text-indent:1em" , ^188m1Tl , , colspan="3" style="text-indent:2em" , 40(30) keV , 71(1) s , β⁺ , ¹⁸⁸Hg , (7+) , , , - , style="text-indent:1em" , ^188m2Tl , , colspan="3" style="text-indent:2em" , 310(30) keV , 41(4) ms , , , (9−) , , , - , ¹⁸⁹Tl , , style="text-align:right" , 81 , style="text-align:right" , 108 , 188.973588(12) , 2.3(2) min , β⁺ , ¹⁸⁹Hg , (1/2+) , , , - , rowspan=2 style="text-indent:1em" , ^189mTl , rowspan=2, , rowspan=2 colspan="3" style="text-indent:2em" , 257.6(13) keV , rowspan=2, 1.4(1) min , β⁺ (96%) , ¹⁸⁹Hg , rowspan=2, (9/2−) , rowspan=2, , rowspan=2, , - , IT (4%) , ¹⁸⁹Tl , - , ¹⁹⁰Tl , , style="text-align:right" , 81 , style="text-align:right" , 109 , 189.97388(5) , 2.6(3) min , β⁺ , ¹⁹⁰Hg , 2(−) , , , - , style="text-indent:1em" , ^190m1Tl , , colspan="3" style="text-indent:2em" , 130(90)# keV , 3.7(3) min , β⁺ , ¹⁹⁰Hg , 7(+#) , , , - , style="text-indent:1em" , ^190m2Tl , , colspan="3" style="text-indent:2em" , 290(70)# keV , 750(40) μs , , , (8−) , , , - , style="text-indent:1em" , ^190m3Tl , , colspan="3" style="text-indent:2em" , 410(70)# keV , >1 μs , , , 9− , , , - , ¹⁹¹Tl , , style="text-align:right" , 81 , style="text-align:right" , 110 , 190.971786(8) , 20# min , β⁺ , ¹⁹¹Hg , (1/2+) , , , - , style="text-indent:1em" , ^191mTl , , colspan="3" style="text-indent:2em" , 297(7) keV , 5.22(16) min , β⁺ , ¹⁹¹Hg , 9/2(−) , , , - , ¹⁹²Tl , , style="text-align:right" , 81 , style="text-align:right" , 111 , 191.97223(3) , 9.6(4) min , β⁺ , ¹⁹²Hg , (2−) , , , - , style="text-indent:1em" , ^192m1Tl , , colspan="3" style="text-indent:2em" , 160(50) keV , 10.8(2) min , β⁺ , ¹⁹²Hg , (7+) , , , - , style="text-indent:1em" , ^192m2Tl , , colspan="3" style="text-indent:2em" , 407(54) keV , 296(5) ns , , , (8−) , , , - , ¹⁹³Tl , , style="text-align:right" , 81 , style="text-align:right" , 112 , 192.97067(12) , 21.6(8) min , β⁺ , ¹⁹³Hg , 1/2(+#) , , , - , rowspan=2 style="text-indent:1em" , ^193mTl , rowspan=2, , rowspan=2 colspan="3" style="text-indent:2em" , 369(4) keV , rowspan=2, 2.11(15) min , IT (75%) , ¹⁹³Tl , rowspan=2, 9/2− , rowspan=2, , rowspan=2, , - , β⁺ (25%) , ¹⁹³Hg , - , rowspan=2, ¹⁹⁴Tl , rowspan=2, , rowspan=2 style="text-align:right" , 81 , rowspan=2 style="text-align:right" , 113 , rowspan=2, 193.97120(15) , rowspan=2, 33.0(5) min , β⁺ , ¹⁹⁴Hg , rowspan=2, 2− , rowspan=2, , rowspan=2, , - , α (10⁻⁷%) , ¹⁹⁰Au , - , style="text-indent:1em" , ^194mTl , , colspan="3" style="text-indent:2em" , 300(200)# keV , 32.8(2) min , β⁺ , ¹⁹⁴Hg , (7+) , , , - , ¹⁹⁵Tl , , style="text-align:right" , 81 , style="text-align:right" , 114 , 194.969774(15) , 1.16(5) h , β⁺ , ¹⁹⁵Hg , 1/2+ , , , - , style="text-indent:1em" , ^195mTl , , colspan="3" style="text-indent:2em" , 482.63(17) keV , 3.6(4) s , IT , ¹⁹⁵Tl , 9/2− , , , - , ¹⁹⁶Tl , , style="text-align:right" , 81 , style="text-align:right" , 115 , 195.970481(13) , 1.84(3) h , β⁺ , ¹⁹⁶Hg , 2− , , , - , rowspan=2 style="text-indent:1em" , ^196mTl , rowspan=2, , rowspan=2 colspan="3" style="text-indent:2em" , 394.2(5) keV , rowspan=2, 1.41(2) h , β⁺ (95.5%) , ¹⁹⁶Hg , rowspan=2, (7+) , rowspan=2, , rowspan=2, , - , IT (4.5%) , ¹⁹⁶Tl , - , ¹⁹⁷Tl , , style="text-align:right" , 81 , style="text-align:right" , 116 , 196.969575(18) , 2.84(4) h , β⁺ , ¹⁹⁷Hg , 1/2+ , , , - , style="text-indent:1em" , ^197mTl , , colspan="3" style="text-indent:2em" , 608.22(8) keV , 540(10) ms , IT , ¹⁹⁷Tl , 9/2− , , , - , ¹⁹⁸Tl , , style="text-align:right" , 81 , style="text-align:right" , 117 , 197.97048(9) , 5.3(5) h , β⁺ , ¹⁹⁸Hg , 2− , , , - , rowspan=2 style="text-indent:1em" , ^198m1Tl , rowspan=2, , rowspan=2 colspan="3" style="text-indent:2em" , 543.5(4) keV , rowspan=2, 1.87(3) h , β⁺ (54%) , ¹⁹⁸Hg , rowspan=2, 7+ , rowspan=2, , rowspan=2, , - , IT (46%) , ¹⁹⁸Tl , - , style="text-indent:1em" , ^198m2Tl , , colspan="3" style="text-indent:2em" , 687.2(5) keV , 150(40) ns , , , (5+) , , , - , style="text-indent:1em" , ^198m3Tl , , colspan="3" style="text-indent:2em" , 742.3(4) keV , 32.1(10) ms , , , (10−)# , , , - , ¹⁹⁹Tl , , style="text-align:right" , 81 , style="text-align:right" , 118 , 198.96988(3) , 7.42(8) h , β⁺ , ¹⁹⁹Hg , 1/2+ , , , - , style="text-indent:1em" , ^199mTl , , colspan="3" style="text-indent:2em" , 749.7(3) keV , 28.4(2) ms , IT , ¹⁹⁹Tl , 9/2− , , , - , ²⁰⁰Tl , , style="text-align:right" , 81 , style="text-align:right" , 119 , 199.970963(6) , 26.1(1) h , β⁺ , ²⁰⁰Hg , 2− , , , - , style="text-indent:1em" , ^200m1Tl , , colspan="3" style="text-indent:2em" , 753.6(2) keV , 34.3(10) ms , IT , ²⁰⁰Tl , 7+ , , , - , style="text-indent:1em" , ^200m2Tl , , colspan="3" style="text-indent:2em" , 762.0(2) keV , 0.33(5) μs , , , 5+ , , , - , ²⁰¹TlMain isotope used in

scintigraphy Scintigraphy (from Latin ''scintilla'', "spark"), also known as a gamma scan, is a diagnostic test in nuclear medicine, where radioisotopes attached to drugs that travel to a specific organ or tissue ( radiopharmaceuticals) are taken internally an ...

, , style="text-align:right" , 81 , style="text-align:right" , 120 , 200.970819(16) , 72.912(17) h , EC , ²⁰¹Hg , 1/2+ , , , - , style="text-indent:1em" , ^201mTl , , colspan="3" style="text-indent:2em" , 919.50(9) keV , 2.035(7) ms , IT , ²⁰¹Tl , (9/2−) , , , - , ²⁰²Tl , , style="text-align:right" , 81 , style="text-align:right" , 121 , 201.972106(16) , 12.23(2) d , β⁺ , ²⁰²Hg , 2− , , , - , style="text-indent:1em" , ^202mTl , , colspan="3" style="text-indent:2em" , 950.19(10) keV , 572(7) μs , , , 7+ , , , - , ²⁰³Tl , , style="text-align:right" , 81 , style="text-align:right" , 122 , 202.9723442(14) , colspan=3 align=center,

Observationally Stable Stable nuclides are nuclides that are not radioactive and so (unlike radionuclides) do not spontaneously undergo radioactive decay. When such nuclides are referred to in relation to specific elements, they are usually termed stable isotopes. Th ...

Believed to undergo α decay to ¹⁹⁹Au , 1/2+ , 0.2952(1) , 0.29494–0.29528 , - , style="text-indent:1em" , ^203mTl , , colspan="3" style="text-indent:2em" , 3400(300) keV , 7.7(5) μs , , , (25/2+) , , , - , rowspan=2, ²⁰⁴Tl , rowspan=2, , rowspan=2 style="text-align:right" , 81 , rowspan=2 style="text-align:right" , 123 , rowspan=2, 203.9738635(13) , rowspan=2, 3.78(2) y , β⁻ (97.1%) , ²⁰⁴Pb , rowspan=2, 2− , rowspan=2, , rowspan=2, , - , EC (2.9%) , ²⁰⁴Hg , - , style="text-indent:1em" , ^204m1Tl , , colspan="3" style="text-indent:2em" , 1104.0(4) keV , 63(2) μs , , , (7)+ , , , - , style="text-indent:1em" , ^204m2Tl , , colspan="3" style="text-indent:2em" , 2500(500) keV , 2.6(2) μs , , , (12−) , , , - , style="text-indent:1em" , ^204m3Tl , , colspan="3" style="text-indent:2em" , 3500(500) keV , 1.6(2) μs , , , (20+) , , , - , ²⁰⁵TlFinal decay product of 4n+1

decay chain In nuclear science, the decay chain refers to a series of radioactive decays of different radioactive decay products as a sequential series of transformations. It is also known as a "radioactive cascade". Most radioisotopes do not decay dire ...

(the Neptunium series) , , style="text-align:right" , 81 , style="text-align:right" , 124 , 204.9744275(14) , colspan=3 align=center, Observationally StableBelieved to undergo α decay to ²⁰¹Au , 1/2+ , 0.7048(1) , 0.70472–0.70506 , - , style="text-indent:1em" , ^205m1Tl , , colspan="3" style="text-indent:2em" , 3290.63(17) keV , 2.6(2) μs , , , 25/2+ , , , - , style="text-indent:1em" , ^205m2Tl , , colspan="3" style="text-indent:2em" , 4835.6(15) keV , 235(10) ns , , , (35/2–) , , , - , ²⁰⁶Tl , Radium E'' , style="text-align:right" , 81 , style="text-align:right" , 125 , 205.9761103(15) , 4.200(17) min , β⁻ , ²⁰⁶Pb , 0− , TraceIntermediate

decay product In nuclear physics, a decay product (also known as a daughter product, daughter isotope, radio-daughter, or daughter nuclide) is the remaining nuclide left over from radioactive decay. Radioactive decay often proceeds via a sequence of steps ( ...

of ²³⁸U , , - , style="text-indent:1em" , ^206mTl , , colspan="3" style="text-indent:2em" , 2643.11(19) keV , 3.74(3) min , IT , ²⁰⁶Tl , (12–) , , , - , ²⁰⁷Tl , Actinium C'' , style="text-align:right" , 81 , style="text-align:right" , 126 , 206.977419(6) , 4.77(2) min , β⁻ , ²⁰⁷Pb , 1/2+ , TraceIntermediate

of ²³⁵U , , - , rowspan=2 style="text-indent:1em" , ^207mTl , rowspan=2, , rowspan=2 colspan="3" style="text-indent:2em" , 1348.1(3) keV , rowspan=2, 1.33(11) s , IT (99.9%) , ²⁰⁷Tl , rowspan=2, 11/2– , rowspan=2, , rowspan=2, , - , β⁻ (.1%) , ²⁰⁷Pb , - , ²⁰⁸Tl , Thorium C" , style="text-align:right" , 81 , style="text-align:right" , 127 , 207.9820187(21) , 3.053(4) min , β⁻ , ²⁰⁸Pb , 5+ , TraceIntermediate

of ²³²Th , , - , ²⁰⁹Tl , , style="text-align:right" , 81 , style="text-align:right" , 128 , 208.985359(8) , 2.161(7) min , β⁻ , ²⁰⁹Pb , 1/2+ , TraceIntermediate decay product of ²³⁷Np , , - , rowspan=2, ²¹⁰Tl , rowspan=2, Radium C″ , rowspan=2 style="text-align:right" , 81 , rowspan=2 style="text-align:right" , 129 , rowspan=2, 209.990074(12) , rowspan=2, 1.30(3) min , β⁻ (99.991%) , ²¹⁰Pb , rowspan=2, (5+)# , rowspan=2, Trace , rowspan=2, , - , β⁻, n (.009%) , ²⁰⁹Pb , - , rowspan=2, ²¹¹Tl , rowspan=2, , rowspan=2 style="text-align:right" , 81 , rowspan=2 style="text-align:right" , 130 , rowspan=2, 210.993480(50) , rowspan=2, 80(16) s , β⁻ (97.8%) , ²¹¹Pb , rowspan=2, 1/2+ , rowspan=2, , rowspan=2, , - , β⁻, n (2.2%) , ²¹⁰Pb , - , rowspan=2, ²¹²Tl , rowspan=2, , rowspan=2 style="text-align:right" , 81 , rowspan=2 style="text-align:right" , 131 , rowspan=2, 211.998340(220)# , rowspan=2, 31(8) s , β⁻ (98.2%) , ²¹²Pb , rowspan=2, (5+) , rowspan=2, , rowspan=2, , - , β⁻, n (1.8%) , ²¹¹Pb , - , rowspan=2, ²¹³Tl , rowspan=2, , rowspan=2 style="text-align:right" , 81 , rowspan=2 style="text-align:right" , 132 , rowspan=2, 213.001915(29) , rowspan=2, 24(4) s , β⁻ (92.4%) , ²¹³Pb , rowspan=2, 1/2+ , rowspan=2, , rowspan=2, , - , β⁻, n (7.6%) , ²¹²Pb , - , rowspan=2, ²¹⁴Tl , rowspan=2, , rowspan=2 style="text-align:right" , 81 , rowspan=2 style="text-align:right" , 133 , rowspan=2, 214.006940(210)# , rowspan=2, 11(2) s , β⁻ (66%) , ²¹⁴Pb , rowspan=2, 5+# , rowspan=2, , rowspan=2, , - , β⁻, n (34%) , ²¹³Pb , - , rowspan=2, ²¹⁵Tl , rowspan=2, , rowspan=2 style="text-align:right" , 81 , rowspan=2 style="text-align:right" , 134 , rowspan=2, 215.010640(320)# , rowspan=2, 10(4) s , β⁻ (95.4%) , ²¹⁵Pb , rowspan=2, 1/2+# , rowspan=2, , rowspan=2, , - , β⁻, n (4.6%) , ²¹⁴Pb , - , rowspan=2, ²¹⁶Tl , rowspan=2, , rowspan=2 style="text-align:right" , 81 , rowspan=2 style="text-align:right" , 135 , rowspan=2, 216.015800(320)# , rowspan=2, 6(3) s , β⁻ , ²¹⁶Pb , rowspan=2, 5+# , rowspan=2, , rowspan=2, , - , β⁻, n (<11.5%) , ²¹⁵Pb

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. Thallium-201 is synthesized by the

of stable thallium in a

, or by the ²⁰³Tl(p, 3n)²⁰¹Pb nuclear reaction in

cyclotron A cyclotron is a type of particle accelerator invented by Ernest O. Lawrence in 1929–1930 at the University of California, Berkeley, and patented in 1932. Lawrence, Ernest O. ''Method and apparatus for the acceleration of ions'', filed: Jan ...

s, as ²⁰¹Pb naturally decays to ²⁰¹Tl afterwards. It is a

radiopharmaceutical Radiopharmaceuticals, or medicinal radiocompounds, are a group of pharmaceutical drugs containing radioactive isotopes. Radiopharmaceuticals can be used as diagnostic and therapeutic agents. Radiopharmaceuticals emit radiation themselves, which ...

, as it has good imaging characteristics without excessive patient radiation dose. It is the most popular isotope used for thallium nuclear

cardiac stress test A cardiac stress test (also referred to as a cardiac diagnostic test, cardiopulmonary exercise test, or abbreviated CPX test) is a cardiological test that measures the heart's ability to respond to external stress in a controlled clinical enviro ...

References

* Isotope masses from: ** * Isotopic compositions and standard atomic masses from: ** ** * Half-life, spin, and isomer data selected from the following sources. ** ** ** {{Navbox element isotopes Thallium