Lead-187

Properties and data of the isotope ¹⁸⁷Pb.

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-187; Pb-187Symbol:¹⁸⁷Pb or 18782PbMass number A:187 (= number of nucleons)Atomic number Z:82 (= number of protons)Neutrons N:105Nucleon pairing (Z - N):even - oddNuclear ratio (N/Z ratio):1.280487804878 (= neutron-proton ratio)Neutron excess (N-Z):23Isotopic mass:186.983911(5) u (atomic weight of Lead-187)Nuclide mass:186.9389326 u (calculated nuclear mass without electrons)Mass excess:-14.98681 MeVMass defect:1.567557804 u (per nucleus)Nuclear binding energy:1460.17068908 MeV (per nucleus)
7.80839941 MeV (average binding energy per nucleon)Separation energy:S_N = 8.376(12) MeV (first neutron)
S_P = 2.389(23) MeV (first proton)Half-life:15.2(3) sDecay constant λ:0.045601788194733 s^-1Specific activity α:1.476453720288 × 10⁺²⁰ Bq g^-1
3990415460.2395 Ci g^-1Spin and parity:
(nuclear angular momentum)(3/2-)Charge radius:5.4079(26) femtometer fmYear of discovery:1972

Radioactive Decay

Half-life T_½ = 15.2(3) s respectively 1.52 × 10¹ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	¹⁸³Hg	9.5(20) %	6.393(6) MeV
β⁺	¹⁸⁷Tl	90.5(20) %	7.458(10) MeV

Parent Nuclides

Direct parent isotopes are: ¹⁹¹Po, ¹⁸⁶Bi.

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
^187mPb	33(13) keV	18.3(3) s	(13/2+)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 105) and isobaric (same nucleon number A = 187) with Lead-187. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 105	Isobar A = 187
63	¹⁶⁸Eu
64	¹⁶⁹Gd
65	¹⁷⁰Tb
66	¹⁷¹Dy
67	¹⁷²Ho
68	¹⁷³Er
69	¹⁷⁴Tm
70	¹⁷⁵Yb
71	¹⁷⁶Lu	¹⁸⁷Lu
72	¹⁷⁷Hf	¹⁸⁷Hf
73	¹⁷⁸Ta	¹⁸⁷Ta
74	¹⁷⁹W	¹⁸⁷W
75	¹⁸⁰Re	¹⁸⁷Re
76	¹⁸¹Os	¹⁸⁷Os
77	¹⁸²Ir	¹⁸⁷Ir
78	¹⁸³Pt	¹⁸⁷Pt
79	¹⁸⁴Au	¹⁸⁷Au
80	¹⁸⁵Hg	¹⁸⁷Hg
81	¹⁸⁶Tl	¹⁸⁷Tl
82	¹⁸⁷Pb	¹⁸⁷Pb
83	¹⁸⁸Bi	¹⁸⁷Bi
84	¹⁸⁹Po	¹⁸⁷Po
85	¹⁹⁰At