[Dan1195]

Been thinking about this a bit, and I guess it is really just theoretical conjecture at this point. But what it the highest Z (atomic number) or A (Mass) you can get to before instability (due to fission primarily although one might expect beyond N=184 alpha decay lifetimes will continue to decrease along the stability line) brings all nuclei lifetimes to say nanoseconds or less?

I have seen one theoretical chart from a recent conference presentation that suggests few atoms above Z=126 will survive long enough to identify even if the appropriate projectile and target were available to make them.

Of course there are possibility such as additional deformed shell enclosures providing pockets of stability, etc.

A more practical issue is potential synthesis. Declining cross sections and the fact the resulting nucleus will be farther and farther from the beta stability line will result (I suspect) future synthesis beyond Z=120-122 impractical without some breakthrough in detector technology or some way to significantly increase cross sections. Say even if Z=164 was a mroe stable area due to large shell corrections (as has often been suggested). I think you can forget about ever fusing two lead atoms to get there.

Would probably require what would amount to really radical ideas. Somehow compressing a ton of nuclear matter together to create "huge" atoms which then decay? Some guys in the Ukraine (look up "Proton-21" for a laugh) had claimed a couple years back to make superheavy nuclei by compressing matter w/beams of electrons, but they only reported their stuff at "Cold Fusion" conferences (the nonsense kind) and never said exactly what they did because they were trying to "patent" the process so i took it with as much seriously as Marinarov's claims about element 122 and those "long lived isomeric states".

[gippgig]

There are neutron stars (which of course are giant atomic nuclei) & black holes (which do eventually decay but last much longer than nanoseconds unless they are extremely small).
There is also speculation about toroidal nuclei, nuclear matter containing strange quarks,  and probably others...

[Dan1195]

There are neutron stars (which of course are giant atomic nuclei) & black holes (which do eventually decay but last much longer than nanoseconds unless they are extremely small).
There is also speculation about toroidal nuclei, nuclear matter containing strange quarks,  and probably others...

Have disregarded neutron stars since solely gravity is holding the matter together. Have read some stuff on semi-bubble and bubble nuclei. At this point how stable they are against fission is still a very open question.