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Actinium-224

Properties and data of the isotope 224Ac.

 

Actinium-224 is the radioisotope of the element actinium, whose atomic nucleus has 135 neutrons in addition to the element-specific 89 protons, resulting in a mass number of 224.

See also: list of Actinium isotopes.

 

General data

Name of the isotope:Actinium-224; Ac-224Symbol:224AcMass number A:224Atomic number Z:89 (= number of protons)Neutrons N:135Isotopic mass:224.021722(4) u (atomic weight of Actinium-224)Nuclide mass:223.9729046 u (calculated nuclear mass without electrons)Mass excess:20.23391 MeVMass defect:1.844469508 u (per nucleus)Nuclear binding energy:1718.11227988 MeV (per nucleus)
7.67014411 MeV (average binding energy per nucleon)
Separation energy:SN = 5.663(8) MeV (first neutron)
SP = 4.288(4) MeV (first proton)
Half-life:2.78(16) hDecay constant λ:6.925931060750 × 10-5 s-1Spin and parity:(0-)Year of discovery:1948

 

Radioactive Decay

Half-life T½ = 2.78(16) h (hours) respectively 1.0008 × 104 seconds s.

Decay modeDaughterProbabilityDecay energyγ energy
(intensity)
α220Fr9,1 %6,3269(7) MeV
EE224Ra90,9 %1,408(4) MeV

 

Actinium-224 radioactive decay scheme

 

Parent Nuclides

Direct parent isotope is: 228Pa.

 

Occurrence

Comparison of the natural Actinium isotopes including isotopic abundance (proportion of the isotope mixture):

 

Atomic Mass maQuantityHalf-lifeSpin
Actinium
Isotopic mixture
227,027752408 u100 %
Isotope 223Ac223,019137(8) utrace2.10(5) min(5/2-)
Isotope 224Ac224,021722(4) utrace2.78(16) h(0-)
Isotope 227Ac227,0277507(21) u100 %21.772(3) a3/2-

 

Radiation Protection

The German Radiation Protection Ordinance, for example, specifies the following limit values for the isotope Actinium-224 (exemption limits, clearance values and other values as a radioactive or highly radioactive source of radiation (HASS)):

Isotope:Ac-224+Exemption level:106 BqExemption level per gram:100 Bq/g
Unrestricted handling of solids and liquids.
Half-life:2.8 h

 

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 135) and isobaric (same nucleon number A = 224) with Actinium-224. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

 

OZIsotone N = 135Isobar A = 224
80215Hg
81216Tl
82217Pb
83218Bi224Bi
84219Po224Po
85220At224At
86221Rn224Rn
87222Fr224Fr
88223Ra224Ra
89224Ac224Ac
90225Th224Th
91226Pa224Pa
92227U224U
93228Np
94229Pu
95230Am

 

External data and identifiers

Adopted Levels, Gammas:NuDat 224Ac

 


Category: Isotopes

Last update: 26.11.2022



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