We don't know. No one could.
We have 92 currently known NATURALLY OCCURRING elements and 24 artificial elements.
However, when someone using a particle accelerator smacks lighter nuclei into each other, and devise heavier than ^92^U^238^ elements, they tend to be decidedly unfriendly. ^94^Pu^239^ is used to make nuclear weapons, but is more miserable to separate from ^94^Pu^241^ than it is to separate ^92^U^235^ from ^92^U^238^. How, I refuse to say.
To date, we have documented 2,049 isotopes, and another 223 postulated elements, then we begin a physicist's nightmare talking about positive and negative exotics -- respectively heavier and lighter than our space/time will allow to exist here.
Exotic elements include some truly bizarre lightweights like Positronium (Ps): postulated to be a positron and electron in orbit around each other. In our space, it doesn't stand a prayer: it is like playing marbles encased in cold road tar.
In lower-dimensional space, Ps and other exotics don't have the C limitation to fret over. In our heavy space, the positron and electron move a few angstroms at a time (maintaining .92C) and change back and forth to high-energy gamma radiation.
In higher-dimsnsional space, our baryons compact down a full dimension, showing a whole range of elements that would fly apart here. Mass that comes in from higher dimensional space, of course, comes instantly apart at the seams, resulting in gamma-ray bursts. Note also that our weakest fundamental force, gravity, comes from higher dimensions and is but a weak signal by the time it arrives here.
Just remember that E=MC^2 applies to all dimensions, not just ours.