Promethium-156

Properties and data of the isotope ¹⁵⁶Pm.

Content

General data

Name of the isotope:Promethium-156; Pm-156Symbol:¹⁵⁶Pm or 15661PmMass number A:156 (= number of nucleons)Atomic number Z:61 (= number of protons)Neutrons N:95Isotopic mass:155.931117(4) u (atomic weight of Promethium-156)Nuclide mass:155.8976562 u (calculated nuclear mass without electrons)Mass excess:-64.1641 MeVMass defect:1.369376972 u (per nucleus)Nuclear binding energy:1275.56643316 MeV (per nucleus)
8.1767079 MeV (average binding energy per nucleon)Separation energy:S_N = 5.295(6) MeV (first neutron)
S_P = 9.169(10) MeV (first proton)Half-life:26.70(10) sDecay constant λ:0.025960568560298 s^-1Specific activity α:1.008633552736 × 10⁺²⁰ Bq g^-1
2726036629.0176 Ci g^-1Spin and parity:
(nuclear angular momentum)4(+)Year of discovery:1986

Radioactive Decay

Half-life T_½ = 26.70(10) s respectively 2.670 × 10¹ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β^-	¹⁵⁶Sm	100 %	5.197(9) MeV

Parent Nuclides

Direct parent isotope is: ¹⁵⁶Nd.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 95) and isobaric (same nucleon number A = 156) with Promethium-156. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 95	Isobar A = 156
55	¹⁵⁰Cs
56	¹⁵¹Ba
57	¹⁵²La	¹⁵⁶La
58	¹⁵³Ce	¹⁵⁶Ce
59	¹⁵⁴Pr	¹⁵⁶Pr
60	¹⁵⁵Nd	¹⁵⁶Nd
61	¹⁵⁶Pm	¹⁵⁶Pm
62	¹⁵⁷Sm	¹⁵⁶Sm
63	¹⁵⁸Eu	¹⁵⁶Eu
64	¹⁵⁹Gd	¹⁵⁶Gd
65	¹⁶⁰Tb	¹⁵⁶Tb
66	¹⁶¹Dy	¹⁵⁶Dy
67	¹⁶²Ho	¹⁵⁶Ho
68	¹⁶³Er	¹⁵⁶Er
69	¹⁶⁴Tm	¹⁵⁶Tm
70	¹⁶⁵Yb	¹⁵⁶Yb
71	¹⁶⁶Lu	¹⁵⁶Lu
72	¹⁶⁷Hf	¹⁵⁶Hf
73	¹⁶⁸Ta	¹⁵⁶Ta
74	¹⁶⁹W
75	¹⁷⁰Re
76	¹⁷¹Os
77	¹⁷²Ir
78	¹⁷³Pt
79	¹⁷⁴Au
80	¹⁷⁵Hg
81	¹⁷⁶Tl