Bismuth-208

Properties and data of the isotope ²⁰⁸Bi.

Contents

General data

Name of the isotope:Bismuth-208; Bi-208Symbol:²⁰⁸Bi or 20883BiMass number A:208 (= number of nucleons)Atomic number Z:83 (= number of protons)Neutrons N:125Isotopic mass:207.9797420(25) u (atomic weight of Bismuth-208)Nuclide mass:207.9342151 u (calculated nuclear mass without electrons)Mass excess:-18.87021 MeVMass defect:1.752850156 u (per nucleus)Nuclear binding energy:1632.76940321 MeV (per nucleus)
7.8498529 MeV (average binding energy per nucleon)Separation energy:S_N = 6.8869(27) MeV (first neutron)
S_P = 3.7071(20) MeV (first proton)Half-life:3.68(4) × 10⁵ aDecay constant λ:5.972703565713 × 10^-14 s^-1Specific activity α:173760686.89552 Bq g^-1
0.00469623478096 Ci g^-1Spin and parity:
(nuclear angular momentum)5+Magnetic dipole moment:μ(μ_N) = + 4.578(13)Quadrupole moment Q:0.51(7) barn (100 fm²)Nuclear g-factor:g_l = 0.9156Charge radius:5.5147(907) femtometer fmYear of discovery:1953

Radioactive Decay

Half-life T_½ = 3.68(4) × 10⁵ a respectively 1.160525 × 10¹³ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EC/β⁺	²⁰⁸Pb	100 %	2.8784(26) MeV

Parent Nuclides

Direct parent isotopes are: ²¹²At, ²⁰⁸Po.

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
^208mBi	1571.1(4) keV	2.58(4) ms	10-

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 125) and isobaric (same nucleon number A = 208) with Bismuth-208. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 125	Isobar A = 208
76	²⁰¹Os
77	²⁰²Ir
78	²⁰³Pt	²⁰⁸Pt
79	²⁰⁴Au	²⁰⁸Au
80	²⁰⁵Hg	²⁰⁸Hg
81	²⁰⁶Tl	²⁰⁸Tl
82	²⁰⁷Pb	²⁰⁸Pb
83	²⁰⁸Bi	²⁰⁸Bi
84	²⁰⁹Po	²⁰⁸Po
85	²¹⁰At	²⁰⁸At
86	²¹¹Rn	²⁰⁸Rn
87	²¹²Fr	²⁰⁸Fr
88	²¹³Ra	²⁰⁸Ra
89	²¹⁴Ac	²⁰⁸Ac
90	²¹⁵Th	²⁰⁸Th
91	²¹⁶Pa
92	²¹⁷U