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Actinium-229

Properties and data of the isotope 229Ac.

 

Actinium-229 is the radioisotope of the element Actinium, whose atomic nucleus has 140 neutrons in addition to the element-specific 89 protons, resulting in a mass number of 229.

See also: list of Actinium isotopes.

 

General data

Name of the isotope:Actinium-229; Ac-229Symbol:229AcMass number A:229Atomic number Z:89 (= number of protons)Neutrons N:140Isotopic mass:229.032947(13) u (atomic weight of Actinium-229)Nuclide mass:228.9841296 u (calculated nuclear mass without electrons)Mass excess:30.68993 MeVMass defect:1.876569088 u (per nucleus)Nuclear binding energy:1748.01284606 MeV (per nucleus)
7.63324387 MeV (average binding energy per nucleon)
Separation energy:SN = 6.276(12) MeV (first neutron)
SP = 5.539(12) MeV (first proton)
Half-life:62.7(5) minDecay constant λ:0.00018410283680211 s-1Spin and parity:(3/2+)Year of discovery:1952

 

Radioactive Decay

Half-life T½ = 62.7(5) min (minutes) respectively 3.765 × 103 seconds s.

Decay modeDaughterProbabilityDecay energyγ energy
(intensity)
β-229Th100 %1,104(12) MeV

 

Actinium-229 radioactive decay

 

Parent Nuclides

Direct parent isotope is: 229Ra.

 

Radiation Protection

The German Radiation Protection Ordinance, for example, specifies the following limit values for the isotope Actinium-229 (exemption limits, clearance values and other values as a radioactive or highly radioactive source of radiation (HASS)):

Isotope:Ac-228Exemption level:106 BqExemption level per gram:10 Bq/g
Unrestricted handling of solids and liquids.
Activity HASS:6 × 109 BqSurface contamination:1 Bq/cm2Half-life:6.1 h

 

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 140) and isobaric (same nucleon number A = 229) with Actinium-229. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

 

OZIsotone N = 140Isobar A = 229
83223Bi
84224Po
85225At229At
86226Rn229Rn
87227Fr229Fr
88228Ra229Ra
89229Ac229Ac
90230Th229Th
91231Pa229Pa
92232U229U
93233Np229Np
94234Pu229Pu
95235Am229Am
96236Cm
97237Bk
98238Cf

 

External data and identifiers

Adopted Levels, Gammas:NuDat 229Ac

 


Category: Isotopes

Last update: 26.11.2022



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