[taxcontrol]

If it only survives for a millisecond or two.... is it really an element? What is the time threshold here? Do microseconds count?

Personally, I would say that any structure that is is not stable for at least 1 second does not qualify as an element. Perhaps a new category of "transitives" could be created to categorize these very short lived atoms.

[zeugma]

Perhaps a new category of "transitives" could be created to categorize these very short lived atoms.

Not a bad idea IMO. 

I'm still interested in seeing if there are any non-transitives beyond the end of the current PT as now known .