Actinium, Ac, is a radioactive transition metal element, found in Group IIIa of the periodic table. It is the first member of the actinide series of inner transition elements.

It has three Isotopes

nuclide                        :      225Ac                    227Ac                    228Ac         

atomic mass              :                                   227.03

natural abundance    :       0%                       trace                    trace

half-life                       :     10 days                21.6 yrs                6.13 h

Actinium 227, which has a half-life of 22 years, is formed by the irradiation of Radium.


Actinium, Ac, was discovered by Andre Debierne in 1899 AD.


Actinium occurs in association with Uranium ores, as a decay product of Uranium-235.


Actinium is used as a source of Neutrons.

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