# Can't nobelium form compounds like other lanthanides/actinides do?

Over the past week I've been browsing through WebElements just to find out some interesting facts/properties about certain elements in the Periodic Table.

I've just come across the uncommon element nobelium and it looks like it doesn't form compounds with anything despite being an actinide. For example, actinium can form Actinium Trichloride and promethium can form Promethium(III) Fluoride.

Is there a reason why nobelium is so 'special'?

• Maybe because we have not been able to do the right experiments yet? When you have to create elements artificially and they decay rapidly, chemistry can get hard to study. – Oscar Lanzi Feb 1 '18 at 21:17
• Beyond number 100, there is practically no chemistry to speak about and no reason to ask why is that so. – Ivan Neretin Feb 1 '18 at 21:42

Wikipedia reports that nobelium does form compounds, but unlike other later actinides it could adopt a +2 oxidation state as well as +3, which complicates identifying specific compounds (e.g. nobelium reacts with chlorine but the specific product is not known). The +2 state is stabilized by the full shell configuration $[\ce{Rn}]5f^{14}$. Experiments in aqueous solution seem to show a preference for the +2 oxidation state, and $\ce{No}^{2+}$ has been coprecipitated into solids. But we have yet to definitively identify a neat nobelium compound in either specific oxidation state.