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The stability has in part been correlated to differences in volatility between the lanthanide metals. [78] In EuB 6 and YbB 6 the metals have an oxidation state of +2 whereas in the rest of the lanthanide hexaborides it is +3. This rationalises the differences in conductivity, the extra electrons in the Ln III hexaborides entering conduction bands.
The hexaborides of the lighter lanthanides (La – Sm) melt without decomposition, EuB 6 decomposes to boron and metal and the heavier lanthanides decompose to LnB 4 with exception of YbB 6 which decomposes forming YbB 12. The stability has in part been correlated to differences in volatility between the lanthanide metals. [34]
Like the lanthanides, all actinides are highly reactive with halogens and chalcogens; however, the actinides react more easily. Actinides, especially those with a small number of 5f-electrons, are prone to hybridization. This is explained by the similarity of the electron energies at the 5f, 7s and 6d shells. Most actinides exhibit a larger ...
The lanthanide and actinide elements ... Thus the main difference in oxidation states, between transition elements and other elements is that oxidation states are ...
Furthermore, since only the first two lanthanides (Ce and Pr) can reach the oxidation state corresponding to the loss of all valence electrons (and Pr needs noble-gas matrix isolation conditions to do so), but the first five actinides can do it (Th, Pa, U, Np, and Pu, although only transiently for Pu), it would seem that the outer electrons of ...
Inconsistencies between theoretical models and known chemical properties thus made it difficult to place these elements in the periodic table. [2] The first appearance of the actinide concept may have been in a 32-column periodic table constructed by Alfred Werner in 1905. Upon determining the arrangement of the lanthanides in the periodic ...
During this period, 5f organometallic science has blossomed, and it is now apparent that the actinides have a rich, intricate, and highly informative organometallic chemistry. Intriguing parallels to and sharp differences from the d-block elements have emerged. Actinides can coordinate the organic active groups or bind to carbon by the covalent ...
While the later actinides from americium onwards are predominantly trivalent and behave more similarly to the corresponding lanthanides, as one would expect from periodic trends, the early actinides up to plutonium (thus including thorium and uranium) have relativistically destabilised and hence delocalised 5f and 6d electrons that participate ...