isotopes of thallium

Thallium (Tl) has 25 isotopes which have atomic masses that range from 184 to 210. 203Tl and 205Tl are the only stable isotopes and 204Tl is the most stable radioisotope with a half-life of 3.78 years.

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]

Standard atomic mass: 204.3833(2) u

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

  • radium EII : 206Tl
  • actinium CII : 207Tl
  • thorium CII : 208Tl
  • radium CII : 210Tl

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)
other features
excitation energy
176Tl 81 95 176.00059(21)# 5.2(+30-14) ms (3-,4-,5-)
177Tl 81 100 176.996427(27) 18(5) ms (1/2+)
177mTl 807(18) keV 230(40) µs (11/2-)
178Tl 81 97 177.99490(12)# 255(10) ms
179Tl 81 98 178.99109(5) 270(30) ms (1/2+)
179mTl 860(30)# keV 1.60(16) ms (9/2-)
180Tl 81 99 179.98991(13)# 1.5(2) s
181Tl 81 100 180.986257(10) 3.2(3) s 1/2+#
181mTl 857(29) keV 1.7(4) ms 9/2-#
182Tl 81 101 181.98567(8) 2.0(3) s 2-#
182m1Tl 100(100)# keV 2.9(5) s (7+)
182m2Tl 600(140)# keV 10-
183Tl 81 102 182.982193(10) 6.9(7) s 1/2+#
183m1Tl 630(17) keV 53.3(3) ms 9/2-#
183m2Tl 976.8(3) keV 1.48(10) µs (13/2+)
184Tl 81 103 183.98187(5) 9.7(6) s 2-#
184m1Tl 100(100)# keV 10# s 7+#
184m2Tl 500(140)# keV >20 ns (10-)
185Tl 81 104 184.97879(6) 19.5(5) s 1/2+#
185mTl 452.8(20) keV 1.93(8) s 9/2-#
186Tl 81 105 185.97833(20) 40# s (2-)
186m1Tl 320(180) keV 27.5(10) s (7+)
186m2Tl 690(180) keV 2.9(2) s (10-)
187Tl 81 106 186.975906(9) ~51 s (1/2+)
187mTl 335(3) keV 15.60(12) s (9/2-)
188Tl 81 107 187.97601(4) 71(2) s (2-)
188m1Tl 40(30) keV 71(1) s (7+)
188m2Tl 310(30) keV 41(4) ms (9-)
189Tl 81 108 188.973588(12) 2.3(2) min (1/2+)
189mTl 257.6(13) keV 1.4(1) min (9/2-)
190Tl 81 109 189.97388(5) 2.6(3) min 2(-)
190m1Tl 130(90)# keV 3.7(3) min 7(+#)
190m2Tl 290(70)# keV 750(40) µs (8-)
190m3Tl 410(70)# keV >1 µs 9-
191Tl 81 110 190.971786(8) 20# min (1/2+)
191mTl 297(7) keV 5.22(16) min 9/2(-)
192Tl 81 111 191.97223(3) 9.6(4) min (2-)
192m1Tl 160(50) keV 10.8(2) min (7+)
192m2Tl 407(54) keV 296(5) ns (8-)
193Tl 81 112 192.97067(12) 21.6(8) min 1/2(+#)
193mTl 369(4) keV 2.11(15) min 9/2-
194Tl 81 113 193.97120(15) 33.0(5) min 2-
194mTl 300(200)# keV 32.8(2) min (7+)
195Tl 81 114 194.969774(15) 1.16(5) h 1/2+
195mTl 482.63(17) keV 3.6(4) s 9/2-
196Tl 81 115 195.970481(13) 1.84(3) h 2-
196mTl 394.2(5) keV 1.41(2) h (7+)
197Tl 81 116 196.969575(18) 2.84(4) h 1/2+
197mTl 608.22(8) keV 540(10) ms 9/2-
198Tl 81 117 197.97048(9) 5.3(5) h 2-
198m1Tl 543.5(4) keV 1.87(3) h 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 1/2+
199mTl 749.7(3) keV 28.4(2) ms 9/2-
200Tl 81 119 199.970963(6) 26.1(1) h 2-
200m1Tl 753.6(2) keV 34.3(10) ms 7+
200m2Tl 762.0(2) keV 0.33(5) µs 5+
201Tl 81 120 200.970819(16) 72.912(17) h 1/2+ Main isotope used in scintigraphy
201mTl 919.50(9) keV 2.035(7) ms (9/2-)
202Tl 81 121 201.972106(16) 12.23(2) d 2-
202mTl 950.19(10) keV 572(7) µs 7+
203Tl 81 122 202.9723442(14) STABLE 1/2+ 0.2952(1) 0.29494-0.29528 One of the two stable thallium isotopes
203mTl 3400(300) keV 7.7(5) µs (25/2+)
204Tl 81 123 203.9738635(13) 3.78(2) a 2- Most stable thallium radioisotope
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 81 124 204.9744275(14) STABLE 1/2+ 0.7048(1) 0.70472-0.70506 One of the two stable thallium isotopes
205m1Tl 3290.63(17) keV 2.6(2) µs 25/2+
205m2Tl 4835.6(15) keV 235(10) ns (35/2-)
206Tl 81 125 205.9761103(15) 4.200(17) min 0-
206mTl 2643.11(19) keV 3.74(3) min (12-)
207Tl 81 126 206.977419(6) 4.77(2) min 1/2+
207mTl 1348.1(3) keV 1.33(11) s 11/2-
208Tl 81 127 207.9820187(21) 3.053(4) min 5(+)
209Tl 81 128 208.985359(8) 2.161(7) min (1/2+)
210Tl 81 129 209.990074(12) 1.30(3) min (5+)#
211Tl 81 130 210.99348(22)# 1# min [>300 ns] 1/2+#
212Tl 81 131 211.99823(32)# 30# s [>300 ns] 5+#

Notes

  • Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
  • Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC which use expanded uncertainties.

References

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