Chemistry of Actinides. Complexes and Solids in Aqueous Medias

Actinides are f-block elements, like the lanthanides, and have a special position in Mendeleev's periodic table of elements, inserted in the 3rd column and 7th row. The actinide element series comprises 15 elements, starting with actinium (Z = 89) and ending with laurencium (Z = 103). They are radioelements in the sense that all their isotopes are unstable, and therefore radioactive. The lifetime of these isotopes is given by their half-life, which varies considerably from one isotope to another. Slightly radioactive isotopes of thorium ( ²³² Th) and uranium ( ²³⁸ U and ²³⁵ U) exist naturally, since their half-life is comparable to or greater than the age of the Earth, 14, 4.5, and 0.7 billion years respectively. They decay very slowly, giving rise to the formation of other actinide isotopes. These three chains of natural radioactive decay are noted by family 4n ( ²³² Th), 4n + 2 ( ²³⁸ U) and 4n + 3 ( ²³⁵ U), which corresponds to the mass number of all the nuclides in the chain. The 4n + 1 family, whose parent nuclide is ²³⁷ Np, has now disappeared, as the radioactive half-life of ²³⁷ Np is around 2.1 million years. In addition, natural nuclear reactions have been involved in isotope formation. Naturally occurring isotopes include ²³⁴ U, ²³⁰ Th and ²³¹ Pa. Artificial isotopes come from nuclear bombs and nuclear reactors. These mainly produce the isotopes ²³⁷ Np, ²³⁹ Pu formed from ²³⁸ U, ²³⁴ U and ²³⁶ U formed from ²³⁵ U, as well as ²³⁸ Pu, ²⁴⁰ Pu, ²⁴¹ Pu, ²⁴² Pu, ²⁴¹ Am, ²⁴³ Am and ²⁴⁴ Cm.

The handling of actinides requires precautions to be taken with regard to their radioactivity (nature of radiation and activity), in line with safety and security requirements. Working with non-radioactive chemical analogues...