Thallium-189

Properties and data of the isotope ¹⁸⁹Tl.

Content

General data

Name of the isotope:Thallium-189; Tl-189Symbol:¹⁸⁹Tl or 18981TlMass number A:189 (= number of nucleons)Atomic number Z:81 (= number of protons)Neutrons N:108Isotopic mass:188.973574(9) u (atomic weight of Thallium-189)Nuclide mass:188.929144 u (calculated nuclear mass without electrons)Mass excess:-24.61566 MeVMass defect:1.59606452 u (per nucleus)Nuclear binding energy:1486.72452399 MeV (per nucleus)
7.86626732 MeV (average binding energy per nucleon)Separation energy:S_N = 10.35(3) MeV (first neutron)
S_P = 1.703(15) MeV (first proton)Half-life:2.3(2) minDecay constant λ:0.0050228056562315 s^-1Specific activity α:1.608938466697 × 10⁺¹⁹ Bq g^-1
434848234.24257 Ci g^-1Spin and parity:
(nuclear angular momentum)(1/2+)Year of discovery:1972

Radioactive Decay

Half-life T_½ = 2.3(2) min (minutes) respectively 1.38 × 10² seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EE/β⁺	¹⁸⁹Hg	100 %	5.01(3) MeV

Parent Nuclides

Direct parent isotope is: ¹⁹³Bi.

Nuclear Isomers

Nuclear isomers or excited states with the activation energy in keV related to the ground state.

Nuclear Isomer	Excitation Energy	Half-life	Spin
^189mTl	281(7) keV	1.4(1) min	(9/2-)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 108) and isobaric (same nucleon number A = 189) with Thallium-189. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 108	Isobar A = 189
66	¹⁷⁴Dy
67	¹⁷⁵Ho
68	¹⁷⁶Er
69	¹⁷⁷Tm
70	¹⁷⁸Yb
71	¹⁷⁹Lu
72	¹⁸⁰Hf	¹⁸⁹Hf
73	¹⁸¹Ta	¹⁸⁹Ta
74	¹⁸²W	¹⁸⁹W
75	¹⁸³Re	¹⁸⁹Re
76	¹⁸⁴Os	¹⁸⁹Os
77	¹⁸⁵Ir	¹⁸⁹Ir
78	¹⁸⁶Pt	¹⁸⁹Pt
79	¹⁸⁷Au	¹⁸⁹Au
80	¹⁸⁸Hg	¹⁸⁹Hg
81	¹⁸⁹Tl	¹⁸⁹Tl
82	¹⁹⁰Pb	¹⁸⁹Pb
83	¹⁹¹Bi	¹⁸⁹Bi
84	¹⁹²Po	¹⁸⁹Po
85	¹⁹³At
86	¹⁹⁴Rn