稀土元素铕的4f~76s~2电子层结构决定它除了以正常的+3价态存在之外,还可以+2价的形式存在。铕(Ⅱ)与三价镧系离子性质上的显著差异对于铕的分析和分离有着重要的意义。由于E°Eu~(3+)/Eu~(2+)很低(-0.35V),所以Eu(Ⅱ)很容易被空气中的O_2所氧化,甚至也能被水中的H~+所氧化。因此,在水溶液中获得铕(Ⅱ)以后,使它得以稳定而不被氧化是个很重要的课题。 The 4f ~ 76s ~ 2 electron layer structure of rare earth element europium determines that it exists in the form of +2 valence besides its normal +3 valence state. The significant difference in the properties of europium (Ⅱ) and the trivalent lanthanide series ions is of great significance for the analysis and separation of europium. Eu (II) is easily oxidized by O 2 in the air and can even be oxidized by H ~ + in water due to the low E ° Eu 3+ / Eu 2+ (-0.35 V) . Therefore, it is a very important issue to obtain europium (II) in aqueous solution to stabilize it without being oxidized.