Bismuth-191

Properties and data of the isotope ¹⁹¹Bi.

Contents

General data

Name of the isotope:Bismuth-191; Bi-191Symbol:¹⁹¹Bi or 19183BiMass number A:191 (= number of nucleons)Atomic number Z:83 (= number of protons)Neutrons N:108Isotopic mass:190.985787(8) u (atomic weight of Bismuth-191)Nuclide mass:190.9402601 u (calculated nuclear mass without electrons)Mass excess:-13.23932 MeVMass defect:1.599501584 u (per nucleus)Nuclear binding energy:1489.92612849 MeV (per nucleus)
7.80066036 MeV (average binding energy per nucleon)Separation energy:S_N = 10.711(24) MeV (first neutron)
S_P = 0.112(15) MeV (first proton)Half-life:12.4(3) sDecay constant λ:0.055898966174189 s^-1Specific activity α:1.771744464346 × 10⁺²⁰ Bq g^-1
4788498552.2873 Ci g^-1Spin and parity:
(nuclear angular momentum)(9/2-)Year of discovery:1972

Radioactive Decay

Half-life T_½ = 12.4(3) s respectively 1.24 × 10¹ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	¹⁸⁷Tl	51(10) %	6.78(3) MeV
EC/β⁺	¹⁹¹Pb	49(10) %	6.99(4) MeV

Parent Nuclides

Direct parent isotope is: ¹⁹⁵At.

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
^191m1Bi	240(4) keV	125(13) ms	(1/2+)
^191m2Bi	429.7(4) keV	562(10) ns	(13/2+)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 108) and isobaric (same nucleon number A = 191) with Bismuth-191. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

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