Thulium-156

Properties and data of the isotope ¹⁵⁶Tm.

Contents

General data

Name of the isotope:Thulium-156; Tm-156Symbol:¹⁵⁶Tm or 15669TmMass number A:156 (= number of nucleons)Atomic number Z:69 (= number of protons)Neutrons N:87Isotopic mass:155.938986(15) u (atomic weight of Thulium-156)Nuclide mass:155.9011374 u (calculated nuclear mass without electrons)Mass excess:-56.83417 MeVMass defect:1.3547889 u (per nucleus)Nuclear binding energy:1261.97773162 MeV (per nucleus)
8.08960084 MeV (average binding energy per nucleon)Separation energy:S_N = 8.280(17) MeV (first neutron)
S_P = 1.914(15) MeV (first proton)Half-life:83.8(18) sDecay constant λ:0.0082714460687344 s^-1Specific activity α:3.213665376857 × 10⁺¹⁹ Bq g^-1
868558209.96143 Ci g^-1Spin and parity:
(nuclear angular momentum)2-Charge radius:5.0976(135) femtometer fmYear of discovery:1971

Radioactive Decay

Half-life T_½ = 83.8(18) s respectively 8.38 × 10¹ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EE/β⁺	¹⁵⁶Er	99.936(10) %	7.377(28) MeV
α	¹⁵²Ho	0.064(10) %	4.345(7) MeV

Parent Nuclides

Direct parent isotope is: ¹⁵⁶Yb.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 87) and isobaric (same nucleon number A = 156) with Thulium-156. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 87	Isobar A = 156
49	¹³⁶In
50	¹³⁷Sn
51	¹³⁸Sb
52	¹³⁹Te
53	¹⁴⁰I
54	¹⁴¹Xe
55	¹⁴²Cs
56	¹⁴³Ba
57	¹⁴⁴La	¹⁵⁶La
58	¹⁴⁵Ce	¹⁵⁶Ce
59	¹⁴⁶Pr	¹⁵⁶Pr
60	¹⁴⁷Nd	¹⁵⁶Nd
61	¹⁴⁸Pm	¹⁵⁶Pm
62	¹⁴⁹Sm	¹⁵⁶Sm
63	¹⁵⁰Eu	¹⁵⁶Eu
64	¹⁵¹Gd	¹⁵⁶Gd
65	¹⁵²Tb	¹⁵⁶Tb
66	¹⁵³Dy	¹⁵⁶Dy
67	¹⁵⁴Ho	¹⁵⁶Ho
68	¹⁵⁵Er	¹⁵⁶Er
69	¹⁵⁶Tm	¹⁵⁶Tm
70	¹⁵⁷Yb	¹⁵⁶Yb
71	¹⁵⁸Lu	¹⁵⁶Lu
72	¹⁵⁹Hf	¹⁵⁶Hf
73	¹⁶⁰Ta	¹⁵⁶Ta
74	¹⁶¹W	¹⁵⁶W
75	¹⁶²Re
76	¹⁶³Os
77	¹⁶⁴Ir