Actinium-223 is the short-lived and only artificially accessible radioisotope of the element Actinium, whose atomic nucleus has 134 neutrons in addition to the element-specific 89 protons, resulting in a mass number of 223: 223Ac.
See also: List of individual Actinium isotopes (and general data sources).
General data
Name of the isotope:Actinium-223; Ac-223Symbol:223Ac or 22389AcMass number A:223 (= number of nucleons)Atomic number Z:89 (= number of protons)Neutrons N:134Nucleon pairing (Z - N):odd - evenNuclear ratio (N/Z ratio):1.5056179775281 (= neutron-proton ratio)Neutron excess (N-Z):45Isotopic mass:223.019137(8) u (atomic weight of Actinium-223)Nuclide mass:222.9703196 u (calculated nuclear mass without electrons)Mass excess:17.826 MeVMass defect:1.838389592 u (per nucleus)Nuclear binding energy:1712.44887461 MeV (per nucleus) 7.67914294 MeV (average binding energy per nucleon)Separation energy:SN = 6.867(9) MeV (first neutron) SP = 3.783(8) MeV (first proton)Half-life:2.10(5) minDecay constant λ:0.0055011680996821 s-1Specific activity α:1.485469322783 × 10+19 Bq g-1 401478195.34681 Ci g-1Spin and parity: (nuclear angular momentum)(5/2-)Year of discovery:1948
Radioactive Decay
Half-life T½ = 2.10(5) min (minutes) respectively 1.26 × 102 seconds s.
The following table shows the atomic nuclei that are isotonic (same neutron number N = 134) and isobaric (same nucleon number A = 223) with Actinium-223. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.
