aktinoidi

Aktinoidi is a group of radioactive and metallic elements with atomic numbers ranging from 89 to 103. The series was discovered in the late 19th century and comprises ten elements, as follows: aktinium, thorium, protaktinium, uran, neptun, pluton, americ, krium, berkelij and kalifornij.

The term "aktinoidi" was introduced by the chemistry professor of the University of St. Petersburg, Vladimir Iľjič Ulianov, with other Russian scientists in 1925. It was derived from the Greek word "aktin," meaning ray, in reference to the strong rays emitted by this family of elements.

A characteristic feature of the aktinoidi is their strong chemical similarity to one another. This results from the concentration of electrons in the outermost 5f and 6d orbitals, similar to the case of lanthanoidi. Due to this phenomenon, the periodic table of elements undergoes a smooth continuity without a sharp separation between lanthanoidi and aktinoidi.

The aktinoidi are materials of significant scientific and practical interest. Their earliest investigational isolation is a challenging task for chemists and nuclear physicists due to radioactivity, short(lived isotopes) and rare occurrence. Isolation of single atoms usually requires methods of ionised beam technology.