Lead-212

Properties and data of the isotope ²¹²Pb.

Contents

General Data

Radioactive Decay

Radiation emissions

Parent Nuclides

Isotones und Isobares

Literature

Lead-212 is a radioisotope of the chemical element lead, which has 130 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 212.

The radioactive nuclide was first described in a paper published in 1905 [1] which describes the measurements of the decay curves of the excited states after the decay of radon-220, which was then still referred to as emanation.

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

General data

Name of the isotope:Lead-212; Pb-212Other names:Thorium BSymbol:²¹²Pb or 21282PbMass number A:212 (= number of nucleons)Atomic number Z:82 (= number of protons)Neutrons N:130Nucleon pairing (Z - N):even - evenNuclear ratio (N/Z ratio):1.5853658536585 (= neutron-proton ratio)Neutron excess (N-Z):48Isotopic mass:211.9918959(20) u (atomic weight of Lead-212)Nuclide mass:211.9469175 u (calculated nuclear mass without electrons)Mass excess:-7.54892 MeVMass defect:1.776195804 u (per nucleus)Nuclear binding energy:1654.51573425 MeV (per nucleus)
7.8043195 MeV (average binding energy per nucleon)Separation energy:S_N = 5.1272(25) MeV (first neutron)
S_P = 8.760(42) MeV (first proton)Half-life:10.622(7) hDecay constant λ:1.81267078260 × 10^-5 s^-1Specific activity α:5.17353496944 × 10⁺¹⁶ Bq g^-1
1398252.6944451 Ci g^-1Spin and parity:
(nuclear angular momentum)0+Charge radius:5.5396(19) femtometer fmYear of discovery:1905

Radioactive Decay

Lead-212 occurs as a natural decay product in various natural decay processes - for example, in the thorium series starting from thorium-232; see also parent nuclides below - and initially decays to bismuth-212. The end product is the stable isotope lead-208.

Half-life T_½ = 10.622(7) h (hours) respectively 3.8239 × 10⁴ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β^-	²¹²Bi	100 %	0.5690(18) MeV

Lead-212 gamma emissions

E_γ	I_γ	Dose (MeV/Bq-s)
115.183(5) keV	0.596(9) %	0.000687(11)
176.68(5) keV	0.052(6) %	0.000092(11)
238.632(2) keV	43.6(5) %	0.1040(13)
300.087(10) keV	3.30(4) %	0.00990(13)
415.2 keV	0.0131(22) %	0.0000054(9)

Interfering nuclides in gamma spectrometric determination: thorium-227 (E_γ = 300.50 keV; I_γ = 0.014 %); protactinium-231 (E_γ = 300.06 keV; I_γ = 2.41 %).

Starting nuclides and radioactive decay chain of lead-212

Parent Nuclides

Direct parent isotopes are: ²¹²Tl, ²¹⁶Po, ²²⁶Ra, ²³²Th.

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
^212mPb	+x keV	5(1) μs

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 130) and isobaric (same nucleon number A = 212) with Lead-212. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 130	Isobar A = 212
78	²⁰⁸Pt
79	²⁰⁹Au
80	²¹⁰Hg	²¹²Hg
81	²¹¹Tl	²¹²Tl
82	²¹²Pb	²¹²Pb
83	²¹³Bi	²¹²Bi
84	²¹⁴Po	²¹²Po
85	²¹⁵At	²¹²At
86	²¹⁶Rn	²¹²Rn
87	²¹⁷Fr	²¹²Fr
88	²¹⁸Ra	²¹²Ra
89	²¹⁹Ac	²¹²Ac
90	²²⁰Th	²¹²Th
91	²²¹Pa	²¹²Pa
92	²²²U
93	²²³Np

External data and identifiers

CAS:15092-94-1InChI Key:WABPQHHGFIMREM-BKFZFHPZSA-NSMILES:[212Pb]PubChem:ID 6335491Adopted Levels, Gammas:NuDat 212Pb

Literature and References

[0] - Research articles in scientific journals via PubMed: 212Pb.

[1] - Ernest Rutherford, F. R. S.:
V. Bakerian Lecture. - The succession of changes radioactive bodies.
In: Philosophical Transactions A, 204, 372-386, (1905), DOI 10.1098/rsta.1905.0005.

[2] - Rachel Roberts, Tim Carthy, Jennifer Young et al.:
Minimising the impact of stable ²⁰⁸Pb on recovery of ²¹²Pb from a generator.
In: EJNMMI Radiopharmacy and Chemistry, 10, 49, (2025), DOI 10.1186/s41181-025-00357-4.

[3] - Jarred Michael Scaffidi-Muta, Andrew David Abell:
²¹²Pb in targeted radionuclide therapy: a review.
In: EJNMMI Radiopharmacy and Chemistry, 10, 34, (2025), DOI 10.1186/s41181-025-00362-7.