Actinides

A common feature of actinides is the possession of multiple oxidation states. The term oxidation state refers to the number of electron(s) that are involved or that can possibly become involved in the formation of chemical bond(s) in that compound, when one element combines with another element during a chemical reaction. The oxidation state is designated by a plus sign (when an electron is donated or electro-positive) or by a minus sign (when the electron is accepted or electronegative). An element can have more than one oxidation state. An electron configuration can provide the information about the oxidation state of that element. The most predominant oxidation state among actinides is +3, which is similar to lanthanides. The crystal structure (geometry), solubility property, and the formation of chemical compounds are based on the oxidation state of the given element.

Actinides ions in an aqueous solution are colorful, containing colors such as red purple (U³⁺), purple (Np³⁺), pink (Am³⁺), green (U⁴⁺), yellow green (Np⁴⁺), and pink red (Am⁴⁺). Actinides ions U, Np, Pu, and Am undergo hydrolysis, disproportionation, or formation of polymeric ions in aqueous solutions with a low pH.

All actinides are characterized by partially filled 5f, 6d, and 7s orbitals. Actinides form complexes easily with certain ligands as well as with halide, sulfate, and other ions. Organometallic compounds (compounds with a sign bond between the meta and carbon atom of organic moiety) of uranium and thorium have been prepared and are useful in organic synthesis. Several alloys of protactinium with uranium have been prepared.