Transthorium elements

In the transthorium elements (with Z above 90) there was around 1955 a controversy 16 17) whether some 6 d electrons might occur, rather than a partly filled 5 f shell in agreement with Eqs. (4) and (5). The situation seems quite complicated in alloys of protactinium, uranium and neptunium with other metals, whereas plutonium may choose between 5 f4 Pu[IV] and 5 fs Pu[III] in the individual alloys or modifications of the element. On the other hand, americium and curium seem al-... 

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