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Properties and data of the isotope 212Bi.


Bismuth-212 is the radioisotope of the element Bismuth, whose atomic nucleus has 129 neutrons in addition to the element-specific 83 protons, resulting in a mass number of 212.

See also: list of Bismuth isotopes.


General data

Name of the isotope:Bismuth-212; Bi-212Namen:Thorium CSymbol:212BiMass number A:212Atomic number Z:83 (= number of protons)Neutrons N:129Isotopic mass:211.991285(2) u (atomic weight of Bismuth-212)Nuclide mass:211.9457581 u (calculated nuclear mass without electrons)Mass excess:-8.11797 MeVMass defect:1.77596682 u (per nucleus)Nuclear binding energy:1654.30243703 MeV (per nucleus)
7.80331338 MeV (average binding energy per nucleon)
Separation energy:SN = 4.330(6) MeV (first neutron)
SP = 4.9140(27) MeV (first proton)
Half-life:60.55(6) minDecay constant λ:0.00019079195721441 s-1Spin and parity:1(-)Charge radius:5.5489(901) femtometer fmYear of discovery:1905


Radioactive Decay

Half-life T½ = 60.55(6) min (minutes) respectively 3.633 × 103 seconds s.

Decay modeDaughterProbabilityDecay energyγ energy
β-212Po64,06(6) %2,2515(17) MeV
α208Tl35,94(6) %6,20726(3) MeV


Bi-212 is a radioactive intermediate of the thorium series emanating from Thorium-232 (see there for complete decay scheme).


Bismuth-212 radioactive decay


Parent Nuclides

Direct parent isotopes are: 216At, 212Pb.


Radiation Protection

The German Radiation Protection Ordinance, for example, specifies the following limit values for the isotope Bismuth-212 (exemption limits, clearance values and other values as a radioactive or highly radioactive source of radiation (HASS)):

Isotope:Bi-212+Exemption level:105Exemption level per gram:10 Bq/g
Unrestricted handling of solids and liquids.
Activity HASS:0,05 TBqSurface contamination:1 Bq cm-2Half-life:60.5 min


Nuclear Isomers

Nuclear isomers or excited states with the activation energy in keV related to the ground state.

Nuclear IsomerExcitation EnergyHalf-lifeSpin
212m1Bi250 keV25,0(2) Minuten(8-,9-)
212m2Bi1910 keV7,0(3) Minuten


Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 129) and isobaric (same nucleon number A = 212) with Bismuth-212. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.


OZIsotone N = 129Isobar A = 212


External data and identifiers

CAS:14913-49-6InChI Key:JCXGWMGPZLAOME-AKLPVKDBSA-NSMILES:[212Bi]PubChem:ID 6335500Adopted Levels, Gammas:NuDat 212Bi


Category: Isotopes

Last update: 26.11.2022

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