Lead-205m2

Properties and data of the isotope ²⁰⁵Pb.

Content

General data

Name of the isotope:Lead-205m2; Pb-205m2Symbol:²⁰⁵Pb or 20582PbMass number A:205 (= number of nucleons)Atomic number Z:82 (= number of protons)Neutrons N:123Isotopic mass:204.9744816(12) u (atomic weight of Lead-205m2)
Excitation energy: 1013.85(3) keVNuclide mass:204.9295032 u (calculated nuclear mass without electrons)Mass excess:-23.77024 MeVMass defect:1.732955692 u (per nucleus)Nuclear binding energy:1614.23782936 MeV (per nucleus)
7.87433087 MeV (average binding energy per nucleon)Half-life:5.55(2) msDecay constant λ:124.89138388467 s^-1Specific activity α:3.686830911499 × 10⁺²³ Bq g^-1
9964407868918.1 Ci g^-1Spin and parity:
(nuclear angular momentum)13/2+

Radioactive Decay

Half-life T_½ = 5.55(2) ms respectively 5.55 × 10^-3 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
Iso	²⁰⁵Pb	100 %

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
²⁰⁵Pb		1.70(9) × 10⁷a	5/2-
^205m1Pb	2.329(7) keV	24.2(4) μs	1/2-
^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-205m2. 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