Actinium, Radioactive

Other Properties

There are 34 isotopes and isomers of actinium(1). Actinium-227 and actinium-228 are the only naturally occurring isotopes(2). Actinium-206 through 226 and 229 through 234 are artificially produced and all are radioactive(2).
Atomic number 89; valence: 3; no stable nuclides; known isotopes (mass numbers): 209-233; naturally occurring isotopes: 227, 228; homologous with lanthanum; more basic than lanthanum; strong electropositive element; forms insoluble salts, e.g., carbonate, oxalate, phosphate, etc., just as the lanthanides; rapidly oxidizes to AcO3 in moist air
/Actinium-225/ Atomic weight = 225.02322; half-life = 10.0 days; alpha emission, 5.935 MeV
/Actinium-227/ Atomic weight = 227.027747; half-life = 21.77 years; negative beta emission, 0.045 MeV; alpha emission, 5.043 MeV
/Actinium-228/ Atomic weight = 228.031014; half-life = 6.15 hours; negative beta emission, 2.127 MeV
DECAY PATHWAY: Actinium-225, half-life 10.0 days, decays via alpha emission, 5.935 MeV, to francium-221, half-life 4.9 minutes. Francium-221 decays via alpha emission, 6.458 MeV, to astatine-227, half-life 32.2 minutes; decays via beta emission, 0.312 MeV, to radium-221, half-life 28 seconds.
DECAY PATHWAY: Actinium-227, half-life 21.77 years, decays via beta emission (98.62%), 0.045 MeV, to thorium-227, half-life 7,340 years. Thorium-227 decays via alpha emission, 6.146 MeV, to radium-223, half-life 11.425 days. Actinium-227 decays via alpha emission (1.38%), 5.043 MeV, to francium-223, half-life 22.00 minutes. Francium-223 decays via beta emission, 1.149 MeV, to radium-223.
DECAY PATHWAY: Actinium-228, half-life 6.15 hours, decays via beta emission, 2.127 MeV, to thorium-228, half-life 1.9116 years.
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