EuropiumII

Europium(II) refers to the divalent oxidation state of europium, commonly written as Eu2+. It is a less stable form than europium(III) in most compounds and in aqueous solutions, where Eu2+ rapidly oxidizes to Eu3+. The Eu2+ ion has a 4f7 electronic configuration, which yields a high-spin ground state (8S7/2) and a relatively large magnetic moment. Because of this electronic structure, Eu2+ compounds can be paramagnetic or, in certain lattices, exhibit ferromagnetic ordering at low temperatures.

Occurrence and compounds are typically restricted to environments that are reducing or where the Eu2+ ion is stabilized by crystal structure. Notable Eu2+ species include europous oxides and chalcogenides such as EuO and EuS, as well as EuX2 (X = F, Cl, Br, I) halides. In many hosts, Eu2+ can be doped into lattices to serve as a luminescent activator. The larger ionic size of Eu2+ relative to Eu3+ influences crystal chemistry, often enabling distinct structural motifs and higher coordination numbers in Eu2+-containing materials.

Reactivity and applications are dominated by the reducing nature of Eu2+. It is easily oxidized by air, making many Eu2+ compounds air-sensitive and requiring handling under inert atmospheres. Eu2+ is widely used as a luminescent activator in blue-emitting phosphors and certain scintillators, and as a reducing agent in chemical synthesis. In phosphors, Eu2+-doped hosts can produce intense blue emission and have been employed in display technologies and lighting, while in detectors Eu2+-activated materials contribute to scintillation properties.

Overall, europium(II) is characteristic for its instability in air, strong reducing power, magnetic moments from a half-filled 4f shell, and practical applications in luminescent materials.