Lead-205

Properties and data of the isotope ²⁰⁵Pb.

Content

General data

Name of the isotope:Lead-205; Pb-205Symbol:²⁰⁵Pb or 20582PbMass number A:205 (= number of nucleons)Atomic number Z:82 (= number of protons)Neutrons N:123Isotopic mass:204.9744817(12) u (atomic weight of Lead-205)Nuclide mass:204.9295033 u (calculated nuclear mass without electrons)Mass excess:-23.77014 MeVMass defect:1.732955592 u (per nucleus)Nuclear binding energy:1614.23773621 MeV (per nucleus)
7.87433042 MeV (average binding energy per nucleon)Separation energy:S_N = 6.73167(11) MeV (first neutron)
S_P = 6.71306(21) MeV (first proton)Half-life:1.70(9) × 10⁷aDecay constant λ:1.292914877040 × 10^-15 s^-1Specific activity α:3816723.288944 Bq g^-1
0.00010315468348497 Ci g^-1Spin and parity:
(nuclear angular momentum)5/2-Magnetic dipole moment:μ(μ_N) = +0.7117(4)Quadrupole moment Q:+2.26(37) barn (100 fm²)Nuclear g-factor:g_l = 0.28468Charge radius:5.4828(15) femtometer fmYear of discovery:1954

Radioactive Decay

Half-life T_½ = 1.70(9) × 10⁷a respectively 5.36112 × 10¹⁴ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EE	²⁰⁵Tl	100 %	0.0506(17) MeV

Parent Nuclides

Direct parent isotopes are: ²⁰⁵Bi, ²⁰⁹Po.

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
^205m1Pb	2.329(7) keV	24.2(4) μs	1/2-
^205m2Pb	1013.85(3) keV	5.55(2) ms	13/2+
^205m3Pb	3195.7(5) keV	217(5) ns	25/2-

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 123) and isobaric (same nucleon number A = 205) with Lead-205. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 123	Isobar A = 205
74	¹⁹⁷W
75	¹⁹⁸Re
76	¹⁹⁹Os
77	²⁰⁰Ir	²⁰⁵Ir
78	²⁰¹Pt	²⁰⁵Pt
79	²⁰²Au	²⁰⁵Au
80	²⁰³Hg	²⁰⁵Hg
81	²⁰⁴Tl	²⁰⁵Tl
82	²⁰⁵Pb	²⁰⁵Pb
83	²⁰⁶Bi	²⁰⁵Bi
84	²⁰⁷Po	²⁰⁵Po
85	²⁰⁸At	²⁰⁵At
86	²⁰⁹Rn	²⁰⁵Rn
87	²¹⁰Fr	²⁰⁵Fr
88	²¹¹Ra	²⁰⁵Ra
89	²¹²Ac	²⁰⁵Ac
90	²¹³Th
91	²¹⁴Pa
92	²¹⁵U