Transeinsteinium elements

All of the elements listed in table 24 are known or expected to have, under some conditions, gaseous monoxides at high temperatures this is likely to be true for the transeinsteinium elements as well. However, even in the gaseous state, the stability of the monoxide relative to its dissociation to atomic vapor and oxygen changes across the series, so that with increasing Z in each series the monoxide tends to become less... 

Once the existence of a new element had been established, the first experiments performed with it were likely to be done at the tracer level. It took considerable efforts to produce quantities of the element sufficient for solid-state studies, such as obtaining physical properties of its oxide(s). The lack of material is the reason for the void of information for the transeinsteinium elements. 

There has not been any solid-state chemistry reported for pure bulk forms of the transeinsteinium elements, due to the small amounts of the elements that have been available and their short lives. The most abundant of these elements is Fm [nanograms of a very short-lived (20 h) Fm-255 isotope] and the above limitations have precluded studying its oxide. When reaching the end members of the actinide series, the availability of isotopes is a much greater problem e.g., only a few atoms of a short-lived isotope of Lr can be produced. 

Based on speculation, one would expect that the highest oxides formed by the transeinsteinium elements would be their sesquioxides, and the C-type structure would be the favored, or perhaps the only, structural form. A monoxide may become more probable for elements following Fm in the series due to the increased tendency toward divalent stability across the series especially at No. The last member, Lr, almost certainly would form a sesquioxide, based on its filled 5f state (5f, like Lu in the lanthanide series). 

It is not feasible to consider conventional-type studies (structure, vaporization behavior, etc.) for the transeinsteinium oxides, given their scarcity and short lifetimes. Presumably their oxide chemistry would be very similar to that of the lanthanide oxides, especially for the trivalent oxidation state. However, there is an increased tendency for actinides in the second half of the series toward divalency. This suggests that the monoxides of the higher actinides (e.g., transeinsteinium elements) could be potentially more stable, perhaps approaching the stability of Eu monoxide. With No (element 102 homolog of Yb), the monoxide could be its most stable oxide. 

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