Lead-204

Properties and data of the isotope ²⁰⁴Pb.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

Literature

Lead-204 is a quasi stable isotope of the chemical element lead, which has 122 neutrons in its atomic nucleus in addition to the element-specific 82 protons; the sum of the number of these atomic nucleus building blocks results in a mass number of 204.

The nuclide is primordial, meaning that terrestrial Pb-204 deposits have existed since the Earth's formation. The statement of quasistability refers to the assumption that lead-204 could radioactively decay by emitting an alpha particle (a helium-4 nucleus). However, due to the rarity of this event — the half-life for this decay could be around 1.4 × 10¹⁷ years — such alpha decay has not yet been observed.

The discovery of lead-204 using spectroscopic methods was reported in 1932 [1].

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

General data

Name of the isotope:Lead-204; Pb-204Symbol:²⁰⁴Pb or 20482PbMass number A:204 (= number of nucleons)Atomic number Z:82 (= number of protons)Neutrons N:122Nucleon pairing (Z - N):even - evenNuclear ratio (N/Z ratio):1.4878048780488 (= neutron-proton ratio)Neutron excess (N-Z):40Isotopic mass:203.973044(8) u (atomic weight of Lead-204)Nuclide mass:203.9280656 u (calculated nuclear mass without electrons)Mass excess:-25.10935 MeVMass defect:1.725728376 u (per nucleus)Nuclear binding energy:1607.50562787 MeV (per nucleus)
7.87992955 MeV (average binding energy per nucleon)Separation energy:S_N = 8.395(6) MeV (first neutron)
S_P = 6.6375(3) MeV (first proton)Half-life:1.4 × 10¹⁷ aDecay constant λ:1.56892699044 × 10^-25 s^-1Specific activity α:0.00046543346480003 Bq g^-1
1.257928283243 × 10^-14 Ci g^-1Spin and parity:
(nuclear angular momentum)0+Charge radius:5.4803(14) femtometer fmYear of discovery:1932

Radioactive Decay

Half-life T_½ = 1.4 × 10¹⁷ a respectively 4.41796963644288 × 10²⁴ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	²⁰⁰Hg	?	1.9685(11) MeV

Parent Nuclides

Direct parent isotopes are: ²⁰⁴Bi, ²⁰⁸Po, ²⁰⁴Tl.

Occurrence

Comparison of the natural Lead isotopes including isotopic abundance (mole fraction of the isotope mixture in percent):

	Atomic Mass m_a	Quantity	Half-life	Spin
Lead Isotopic mixture	207.2 u	100 %
Isotope ²⁰⁶Pb	205.974466(8) u	24.1(30) %	stable	0+
Isotope ²⁰⁴Pb	203.973044(8) u	1.4(6) %	1.4 × 10¹⁷ a	0+
Isotope ²⁰⁸Pb	207.976653(8) u	52.4(70) %	stable	0+
Isotope ²⁰⁷Pb	206.975897(8) u	22.1(50) %	stable	1/2-

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
^204m1Pb	1274.13(5) keV	265(6) ns	4+
^204m2Pb	2185.88(8) keV	66.93(10) min	9-
^204m3Pb	2264.42(6) keV	0.45(+10-3) μs	7-

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 122) and isobaric (same nucleon number A = 204) with Lead-204. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 122	Isobar A = 204
74	¹⁹⁶W
75	¹⁹⁷Re
76	¹⁹⁸Os
77	¹⁹⁹Ir	²⁰⁴Ir
78	²⁰⁰Pt	²⁰⁴Pt
79	²⁰¹Au	²⁰⁴Au
80	²⁰²Hg	²⁰⁴Hg
81	²⁰³Tl	²⁰⁴Tl
82	²⁰⁴Pb	²⁰⁴Pb
83	²⁰⁵Bi	²⁰⁴Bi
84	²⁰⁶Po	²⁰⁴Po
85	²⁰⁷At	²⁰⁴At
86	²⁰⁸Rn	²⁰⁴Rn
87	²⁰⁹Fr	²⁰⁴Fr
88	²¹⁰Ra	²⁰⁴Ra
89	²¹¹Ac	²⁰⁴Ac
90	²¹²Th
91	²¹³Pa
92	²¹⁴U

External data and identifiers

Adopted Levels, Gammas:NuDat 204Pb

Literature and References

[1] - H. Schüler, E. G. Jones:
Über den spektroskopischen Nachweis einer neuen Blei-Isotope.
In: Naturwissenschaften, 20, 171, (1932), DOI 10.1007/BF01504070.

[2] - J. W. Beeman, F. Bellini, L. Cardani et al.:
New experimental limits on the α decays of lead isotopes.
In: The European Physical Journal A, 49, 50, (2013), DOI 10.1140/epja/i2013-13050-7.