Lead-208m

Properties and data of the isotope ^208mPb.

Contents

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

General data

Name of the isotope:Lead-208m; Pb-208mSymbol:^208mPb or 208m82PbMass number A:208 (= number of nucleons)Atomic number Z:82 (= number of protons)Neutrons N:126Nucleon pairing (Z - N):even - evenNuclear ratio (N/Z ratio):1.5365853658537 (= neutron-proton ratio)Neutron excess (N-Z):44Excitation energy:4895.23(5) keVIsotopic mass:207.976653(8) u (atomic weight of Lead-208m)Nuclide mass:207.9316746 u (calculated nuclear mass without electrons)Mass excess:-21.74759 MeVMass defect:1.75677904 u (per nucleus)Nuclear binding energy:1636.42913509 MeV (per nucleus)
7.86744776 MeV (average binding energy per nucleon)Half-life:0.50(5) μsDecay constant λ:1386294.3611199 s^-1Specific activity α:4.033072423188 × 10⁺²⁷ Bq g^-1
1.090019573834 × 10⁺¹⁷ Ci g^-1Spin and parity:
(nuclear angular momentum)10+

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
²⁰⁸Pb		stable	0+

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 126) and isobaric (same nucleon number A = 208) with Lead-208m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 126	Isobar A = 208
76	²⁰²Os
77	²⁰³Ir
78	²⁰⁴Pt	²⁰⁸Pt
79	²⁰⁵Au	²⁰⁸Au
80	²⁰⁶Hg	²⁰⁸Hg
81	²⁰⁷Tl	²⁰⁸Tl
82	²⁰⁸Pb	²⁰⁸Pb
83	²⁰⁹Bi	²⁰⁸Bi
84	²¹⁰Po	²⁰⁸Po
85	²¹¹At	²⁰⁸At
86	²¹²Rn	²⁰⁸Rn
87	²¹³Fr	²⁰⁸Fr
88	²¹⁴Ra	²⁰⁸Ra
89	²¹⁵Ac	²⁰⁸Ac
90	²¹⁶Th	²⁰⁸Th
91	²¹⁷Pa
92	²¹⁸U
93	²¹⁹Np