Lead-209

Properties and data of the isotope ²⁰⁹Pb.

Contents

General data

Name of the isotope:Lead-209; Pb-209Symbol:²⁰⁹Pb or 20982PbMass number A:209 (= number of nucleons)Atomic number Z:82 (= number of protons)Neutrons N:127Isotopic mass:208.98040(1) u (atomic weight of Lead-209)Nuclide mass:208.9354216 u (calculated nuclear mass without electrons)Mass excess:-18.25728 MeVMass defect:1.761696956 u (per nucleus)Nuclear binding energy:1641.01014433 MeV (per nucleus)
7.85172318 MeV (average binding energy per nucleon)Separation energy:S_N = 3.9374(13) MeV (first neutron)
S_P = 8.1535(21) MeV (first proton)Half-life:3.234(7) hDecay constant λ:5.953645129526 × 10^-5 s^-1Specific activity α:1.72373507692 × 10⁺¹⁷ Bq g^-1
4658743.4511541 Ci g^-1Spin and parity:
(nuclear angular momentum)9/2+Magnetic dipole moment:μ(μ_N) = - 1.4735(16)Quadrupole moment Q:-0.269(165) barn (100 fm²)Nuclear g-factor:g_l = -0.32744444444444Charge radius:5.5100(14) femtometer fmYear of discovery:1940

Radioactive Decay

Half-life T_½ = 3.234(7) h (hours) respectively 1.16424 × 10⁴ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β^-	²⁰⁹Bi	100 %	0.6440(11) MeV

Parent Nuclides

Direct parent isotopes are: ²⁰⁹Tl, ²¹³Po, ²²³Ra, ²³²U, ²³³U.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 127) and isobaric (same nucleon number A = 209) with Lead-209. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 127	Isobar A = 209
76	²⁰³Os
77	²⁰⁴Ir
78	²⁰⁵Pt
79	²⁰⁶Au	²⁰⁹Au
80	²⁰⁷Hg	²⁰⁹Hg
81	²⁰⁸Tl	²⁰⁹Tl
82	²⁰⁹Pb	²⁰⁹Pb
83	²¹⁰Bi	²⁰⁹Bi
84	²¹¹Po	²⁰⁹Po
85	²¹²At	²⁰⁹At
86	²¹³Rn	²⁰⁹Rn
87	²¹⁴Fr	²⁰⁹Fr
88	²¹⁵Ra	²⁰⁹Ra
89	²¹⁶Ac	²⁰⁹Ac
90	²¹⁷Th	²⁰⁹Th
91	²¹⁸Pa
92	²¹⁹U