Actinium, which has the symbol Ac, is a member of the halide series of elements. It is the largest trivalent cation in the periodic table. This ion has an atomic number 89 and an ionic radius of only 2.1 x 10-26 A.
Although actinium is radioactive, it is the least abundant naturally occurring radioactive element. Actinium can be extracted from uranium ores but is impractical because of its relatively low concentration.
Another type of radioactive decay is spontaneous fission. In this decay process, an electron is emitted from the nucleus. The newly formed nucleus then gives off excitation energy in the form of photons.
Actinium is not able to form compounds with alkaline earths. Consequently, actinium is extracted from uranium ores and similar rare earth elements. It is also used in radioimmunotherapy. However, a significant portion of isotope 227> Ac is emitted from nuclear reactors.
Since actinium is relatively electropositive, the element is too reactive for use in compounds. However, it is found in the Earth’s crust. Unlike most rare earth elements, it is not found in igneous rock.
In addition, the ionic radius of actinium is a little larger than lanthanum. Actinium is also the first nonprimordial radioactive element to be isolated. As a result, it gave name to the “actinide” series of elements.
In 1899, French chemist Andre Debeime discovered actinium. The element was named after the French scientist. After a few years, other radioactive elements were also discovered.
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