[metmom]

I would suppose that theoretically there would be none.

Practically, however, there has got to be a limit as those heaviest atoms are extremely unstable and there is probably a point where the instability precludes an chance that the atom would hold together at all.

[The KG9 Kid]

I would expect that these heaviest atoms don’t have a problem existing for the long term at the core of a sufficiently massive star.