Lead-191

Properties and data of the isotope ¹⁹¹Pb.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

See also: List of individual Lead isotopes (and general data sources).

General data

Name of the isotope:Lead-191; Pb-191Symbol:¹⁹¹Pb or 19182PbMass number A:191 (= number of nucleons)Atomic number Z:82 (= number of protons)Neutrons N:109Nucleon pairing (Z - N):even - oddNuclear ratio (N/Z ratio):1.3292682926829 (= neutron-proton ratio)Neutron excess (N-Z):27Isotopic mass:190.97828(4) u (atomic weight of Lead-191)Nuclide mass:190.9333016 u (calculated nuclear mass without electrons)Mass excess:-20.23205 MeVMass defect:1.607848468 u (per nucleus)Nuclear binding energy:1497.70120085 MeV (per nucleus)
7.84136754 MeV (average binding energy per nucleon)Separation energy:S_N = 7.89(4) MeV (first neutron)
S_P = 3.15(4) MeV (first proton)Half-life:1.33(8) minDecay constant λ:0.0086860548942349 s^-1Specific activity α:2.753086636327 × 10⁺¹⁹ Bq g^-1
744077469.27776 Ci g^-1Spin and parity:
(nuclear angular momentum)(3/2-)Charge radius:5.4229(26) femtometer fmYear of discovery:1974

Radioactive Decay

Half-life T_½ = 1.33(8) min (minutes) respectively 7.98 × 10¹ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β⁺	¹⁹¹Tl	99.987 %	6.05(4) MeV
α	¹⁸⁷Hg	0.013(5) %	5.46(4) MeV

Parent Nuclides

Direct parent isotopes are: ¹⁹¹Bi, ¹⁹⁵Po.

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
^191mPb	+x keV	2.18(8) min	(13/2+)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 109) and isobaric (same nucleon number A = 191) with Lead-191. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 109	Isobar A = 191
68	¹⁷⁷Er
69	¹⁷⁸Tm
70	¹⁷⁹Yb
71	¹⁸⁰Lu
72	¹⁸¹Hf
73	¹⁸²Ta	¹⁹¹Ta
74	¹⁸³W	¹⁹¹W
75	¹⁸⁴Re	¹⁹¹Re
76	¹⁸⁵Os	¹⁹¹Os
77	¹⁸⁶Ir	¹⁹¹Ir
78	¹⁸⁷Pt	¹⁹¹Pt
79	¹⁸⁸Au	¹⁹¹Au
80	¹⁸⁹Hg	¹⁹¹Hg
81	¹⁹⁰Tl	¹⁹¹Tl
82	¹⁹¹Pb	¹⁹¹Pb
83	¹⁹²Bi	¹⁹¹Bi
84	¹⁹³Po	¹⁹¹Po
85	¹⁹⁴At	¹⁹¹At
86	¹⁹⁵Rn