Isotopes of thallium

Thallium (Tl) has 37 isotopes with atomic masses that range from 176 to 212. 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 radioisotopes.

Thallium-202 (half-life 12.23 days) can be made in a cyclotron[1] while thallium-204 (half-life 3.78 years) is made by the neutron activation of stable thallium in a nuclear reactor.[2]

In the fully ionized state, the isotope 205Tl becomes beta-radioactive, decaying to 205Pb,[3] but 203Tl remains stable.

Relative atomic mass: 204.3833(2).

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
176Tl 81 95 176.00059(21)# 5.2(+30−14) ms (3–,4–,5–)
177Tl 81 96 176.996427(27) 18(5) ms p 176Hg (1/2+)
α (rare) 173Au
177mTl 807(18) keV 230(40) µs p 176Hg (11/2−)
α 173Au
178Tl 81 97 177.99490(12)# 255(10) ms α 174Au
p (rare) 177Hg
179Tl 81 98 178.99109(5) 270(30) ms α 175Au (1/2+)
p (rare) 178Hg
179mTl 860(30)# keV 1.60(16) ms α 175Au (9/2−)
IT (rare) 179Tl
180Tl 81 99 179.98991(13)# 1.5(2) s α (75%) 176Au
β+ (25%) 180Hg
SF (10−4%) 100Ru, 80Kr[5]
181Tl 81 100 180.986257(10) 3.2(3) s α 177Au 1/2+#
β+ 181Hg
181mTl 857(29) keV 1.7(4) ms α 177Au 9/2−#
β+ 181Hg
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 >20 ns (10−)
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 3] 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 4] 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 5] 81 124 204.9744275(14) Observationally stable[n 6] 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 7]
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 8]
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 9]
209Tl 81 128 208.985359(8) 2.161(7) min β 209Pb (1/2+)
210Tl Radium C″ 81 129 209.990074(12) 1.30(3) min β (99.991%) 210Pb (5+)# Trace[n 7]
β, n (.009%) 209Pb
211Tl 81 130 210.99348(22)# 1# min
[>300 ns]
1/2+#
212Tl 81 131 211.99823(32)# 30# s
[>300 ns]
5+#
  1. Abbreviations:
    EC: Electron capture
    IT: Isomeric transition
  2. Bold for stable isotopes
  3. Main isotope used in scintigraphy
  4. Believed to undergo α decay to 199Au
  5. Final decay product of 4n+1 decay chain (the Neptunium series)
  6. Believed to undergo α decay to 201Au
  7. 1 2 Intermediate decay product of 238U
  8. Intermediate decay product of 235U
  9. Intermediate decay product of 232Th

Notes

References

Isotopes of mercury Isotopes of thallium Isotopes of lead
Table of nuclides
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