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Actinium-231

Properties and data of the isotope 231Ac.

 

Actinium-231 is the radioisotope of the element Actinium, whose atomic nucleus has 142 neutrons in addition to the element-specific 89 protons, resulting in a mass number of 231: 231 Ac.

See also: list of Actinium isotopes.

 

General data

Name of the isotope:Actinium-231; Ac-231Symbol:231AcMass number A:231Atomic number Z:89 (= number of protons)Neutrons N:142Isotopic mass:231.038393(14) u (atomic weight of Actinium-231)Nuclide mass:230.9895756 u (calculated nuclear mass without electrons)Mass excess:35.76285 MeVMass defect:1.88845292 u (per nucleus)Nuclear binding energy:1759.08256426 MeV (per nucleus)
7.61507604 MeV (average binding energy per nucleon)
Separation energy:SN = 6.147(21) MeV (first neutron)
SP = 6.042(17) MeV (first proton)
Half-life:7.5(1) minDecay constant λ:0.001540327067911 s-1Spin and parity:1/2+Year of discovery:1973

 

Radioactive Decay

Half-life T½ = 7.5(1) min (minutes) respectively 4.50 × 102 seconds s.

Decay modeDaughterProbabilityDecay energyγ energy
(intensity)
β-231Th100 %1,947(13) MeV

 

Actinium-231 radioactive decay

 

Parent Nuclides

Direct parent isotope is: 231Ra.

 

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 142) and isobaric (same nucleon number A = 231) with Actinium-231. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

 

OZIsotone N = 142Isobar A = 231
84226Po
85227At
86228Rn
87229Fr231Fr
88230Ra231Ra
89231Ac231Ac
90232Th231Th
91233Pa231Pa
92234U231U
93235Np231Np
94236Pu231Pu
95237Am231Am
96238Cm
97239Bk
98240Cf
99241Es
100242Fm

 

External data and identifiers

Adopted Levels, Gammas:NuDat 231Ac

 


Category: Isotopes

Last update: 03.12.2022



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