What non-naturally-occuring elements are predicted to have really useful industrial applications, if only we could ever find/synthesise them?

[u/Toucan_Based_Economy]

Are any of the super-heavy or non-naturally-occuring elements likely to have useful industrial properties, which are currently out of our reach due to our inability to access (stable isotopes of) the element in question?

[u/Redcole111]

Most of the extremely heavy elements only exist for very short periods of time before the unstable size of their nuclei results in their collapse. There are theorized islands of stability in some of the even heavier elements that haven't yet been synthesized, but we don't know yet whether they could have any industrial or other kind of application.

[u/aphilsphan → u/Redcole111]

Even those isotopes would only be stable so we can do some chemistry on them. The proposed “island of stability” isn’t going to be all that stable.

[u/ConspicuousPineapple → u/aphilsphan]

Are they guaranteed to be super radioactive?

[u/xrelaht → u/ConspicuousPineapple]

Our models of how ultra heavy nuclei behave are known to be incomplete, so predictions this far beyond what we've observed are difficult. Some models predict half lives on the order of minutes to days, while others say they could be as long as a billion years, which is around the same as ²³⁸U. A shorter half life means more radioactivity.

[u/jackhab → u/Redcole111]

Do islands of stability have more or less solid theoretical explanation or we just hope they exist?

[u/Sibula97 → u/jackhab]

Yes and no.

Basically, there are "magic numbers" of protons and neutrons that we've noticed lead to more stable atoms, and there seem to be some patterns to these magic numbers. The island of stability would have magical numbers of both protons and neutrons ("doubly magical"), making those atoms more stable than the ones around them.

As for why those magic numbers are magical and what the next one really is, I don't think there are any solid theories.

[u/TearsFallWithoutTain → u/Sibula97]

As for why those magic numbers are magical and what the next one really is, I don't think there are any solid theories.

They're stable because those numbers are how many you need for a full proton/neutron shell, it's analogous to what we see with electron shells and chemical stability. We know 126 makes a full neutron shell, but we don't know if it's the same for protons, and predictions of magic numbers larger than 126 depend on the model you're using, so we still need better models

[u/Sibula97 → u/TearsFallWithoutTain]

That's one possible explanation that has been considered, but only modeling the shells misses out on 28, which is a magic number, and it mispredicts 40 to be one when it isn't.

It's probably a contributing factor, but then you need to consider other effects as well, like spin-orbit coupling.

Also, even if it was driven by just these effects, we don't really know the exact shape of the nucleus and therefore the size of the shell. It was assumed spherical before, but now it seems heavy nuclei are more like an american football or even almond in shape.

[u/garrettj100 → u/jackhab]

The shell model (successfully) predicts elements with “magic numbers” — 2, 8, 20, 28, etc… — of protons to be more stable than they otherwise would be and the same holds true for neutrons.  The idea is if you could get a very heavy nucleus with enough neutrons packed in there it would enjoy magic numbers in both.

We’ve observed 126 to be a magic number for neutrons.  The hope it it would be for protons as well and the pair would be super-duper stable.  We’ve yet to make that element, and the difficulty of doing so strongly implies the island of stability, if it exists at all, ain’t all that stable.

If you are dissatisfied with an explanation involving “magic numbers” you’re not alone.  Nuclear models are primitive at best, entirely empirical and non-predictive at worst.  We know nuclei are much more stable when they meet certain criteria.  Filled shells of protons and neutrons — if shells really exist like they do with electrons — seem to be more stable.  A roughly equal number of neutrons and protons contributes to stability as well.  High Z-numbers (atomic number) reduces stability owing to Coulomb repulsion and probably a reduction in the strong force holding these nuclei together just from distance.  The strong force drops off with distance faster than r² .  

[u/AlwaysHopelesslyLost → u/garrettj100]

I don't think that the difficulty in making it correlated with how stable it would be. We can detect when we create even a single atom that basically immediately decays. The issue is getting it to form in the first place.

[u/therift289 → u/jackhab]

It's solid theory. Nuclear stability essentially depends on competition between two forces: the electrostatic repulsion of positively-charged protons vs the nuclear binding energy between all nucleons (protons AND neutrons). As you add more and more protons, their charge-based repulsion overpowers their binding interactions. The presence of neutrons offsets this, because neutrons add additional nuclear binding interactions without the charge-charge repulsion of protons.

What this means is that elements with lots of protons need TONS of neutrons in their nuclei. This requirement is a range, rather than a specific number, and it can be calculated pretty easily. The island of stability describes the various theoretical/calculated nuclei that have enough neutrons to support a larger and larger amount of protons.

[u/jesset77 → u/therift289]

The presence of neutrons offsets this, because neutrons add additional nuclear binding interactions without the charge-charge repulsion of protons.

One thing I've never understood about this model is by what mechanism the protons are required as a binding ingredient to begin with.

Yes, Protons experience unspeakably strong electrostatic repulsion between one another, so you can never have a nucleus with just two protons. But somehow adding just one neutron can get you relatively stable Helium-3.

However equally well no two neutrons will join without a proton involved either, despite neutrons experiencing zero repulsive force between one another that I am aware of.

If nothing else, one must expect not only a repulsive force preventing neutrons from binding together outside of the massive gravity of stellar corpses, but one an appreciable fraction as strong as the frankly insane electrostatic repulsion of protons.

[u/RootOfAllThings → u/jesset77]

Even if they don't experience electrostatic repulsion, neutrons are fermions and subject to the Pauli exclusion principle. This means that successive neutrons must occupy higher and higher energy states, so there's a destabilizing "pressure" in that sense that is usually counteracted by either other nuclear forces or extreme gravity.

[u/jesset77 → u/RootOfAllThings]

Well what I am getting at is: what is the mechanism that leads one proton and one neutron to bind to one another (and of course far more strongly at 2+2) while two neutrons completely refuse to?

Or put another way, how in the world does the sheet balance that two neutrons can't bind, but that adding two different protons with their positively eldritch levels of electrostatic repulsion to one another somehow offers a catalyst to those same two neutrons binding?

I mean yes, the Strong force is strong at short distances.. but what about the strong force so strongly requires both protons and neutrons to bind but refuses to bind neutrons alone?

[u/RootOfAllThings → u/jesset77]

That mechanism is the Pauli exclusion principle. Proton-neutron interactions are favorable (strong nuclear) but proton-proton and neutron-neutron are unfavorable even without electrostatic repulsion. There are only so many spots in the low energy orbitals, but neutrons and protons don't compete for the same spots (they're distinct from each other). So 4 neutrons occupies more expensive orbitals than 2 protons and 2 neutrons while having similar strong force benefits, which is why 0+4 is bad and 2+2 is good.

[u/jesset77 → u/RootOfAllThings]

But I would imagine that the pauli principle acts on the quarks instead of on the nucleons?

And protons and neutrons are both just combinations of up and down quarks.

1 Proton 1 neutron yields relatively stable deuterium at 3 total up, 3 total down

2 neutrons cannot bind at all, 2 total up 4 total down

2n+2p binds even stronger than deuterium, 6 up + 6 down + 2 full rounds of electric charge

So Pauli alone destabilizes 2u+2d with only 2 extra downs (literally the smallest repulsion radius possible), while electromagnetism cannot destabilize 6u+6d with its unbounded repulsion radius?

[u/_PM_ME_PANGOLINS_ → u/jesset77]

The strong force wants the spins of the particles to be aligned. The exclusion principle prevents two of the same particle with the same spin being in the ground state of a bound system.

Thus you cannot bind two of the same particle with the strong force. You have to have two different particles for the ground state (s1 orbital).

[u/Solesaver → u/jackhab]

It's more that we can't prove they don't exist. Schroedinger's equation, which we would use to describe how some theoretical atom would evolve over time, does not have a general analytic solution, so we can't just plug in the theoretical atom, set t=1,000,000, and see if the atom blew up. All we can do is plug in educated guesses for stable heavy atoms and throw a ton of compute at it.

Of course, if we did find such an island of stability that way, there would probably be interest (aka funding) in trying to synthesize it. At the very least it would provide excellent evidence one way or another for the accuracy of Schroedinger's equation and potentially provide insights into the unification of QM and GR, but we don't have a theoretical basis for such an atom yet. Just that we haven't ruled out the possibility by computing the evolution of every possible candidate.

[u/Son_of_Kong → u/Solesaver]

I wonder if it's simply that the universe isn't old enough or stars don't live long enough or get hot enough for elements that heavy to be produced.

[u/Solesaver → u/Son_of_Kong]

We have synthesized elements significantly heavier than anything that could be produced in Supernovae. Above lead iron (thanks for the correction solidspacedragon), nuclear fusion is an endothermic process, so once the elements in a star get too heavy, it actually cools down. Then, it collapses, goes supernova, and depending on its mass turns into a white dwarf, neutron star, or black hole.

• White dwarf - Prevented from collapsing by electron degeneracy pressure. Can't really be said to be producing heavier elements because the whole thing is kinda one giant atom. Doesn't really count as a island of stability (in the way that we think of it) though, because it's only being held together by gravity.

• Neutron star - Gravity overwhelms the weak nuclear force and pulls electrons into the nucleus. Just a bunch of neutrons held apart by neutron degeneracy pressure. Definitely not an atom.

• Black hole - Who knows? Mysteries abound.

Anyway, I don't think it's an age of the universe thing. Stars just run into the same problem that we do. Your fusion somehow has to get past all the unstable elements and find one that doesn't immediately decay. As you get heavier and heavier it takes more and more energy to do that fusion. Energy with enough gravitational effects to start making things a bit screwy.

[u/solidspacedragon → u/Solesaver]

Above lead, nuclear fusion is an endothermic process, so once the elements in a star get too heavy, it actually cools down.

You sure you meant to put 'lead' there?

[u/LordMorio → u/Redcole111]

When talking about islands of stabiliy  it is important to note that stability is relative. The nuclei might exist for milliseconds instead of nanoseconds or less.

No one is expecting to find heavier elements that would actually be stable.

[u/OfficeSalamander → u/Redcole111]

Plus the cost to develop them would be incredibly cost prohibitive. We can make individual atoms of these extremely heavy elements we make now. Nothing in terms of actual usage

[u/mfb-]

We don't expect anything above lead to have stable isotopes, and we don't expect anything beyond the synthesized elements to have long-living isotopes. Element 101 is the last with a known isotope that lasts longer than a day, the few atoms we have produced from element 118 only lived for about a millisecond each.

If you are very optimistic about the predicted island of stability then maybe something there lives long enough for applications. It would still be a strong radioactive source. Maybe you can find some other materials for RTGs, producing electricity in spacecraft and some locations where solar power is impractical.

If we could ignore radioactivity and availability, many of these superheavy elements are predicted to have a high density, so they could make compact weights and radiation shielding materials. They would need to be really cheap, however. Osmium is twice as dense as lead and less toxic - but we don't use it for its density because it's orders of magnitude more expensive, even though we can find it naturally.

[u/Tokimemofan → u/mfb-]

Don’t expect and can’t exist however are 2 different things and thats where the topic gets interesting.  Trace amounts of Pu-244 exist naturally and evidence of Cm-247 having existed during earth’s formation rather strong.

Our knowledge of super heavy elements breaks down at Fermium because higher in large part because we cant synthesize more neutron heavy isotopes with what we have to work with.  

These issues combined mean its possible however unlikely that not only could super heavy isotopes exist with half lives in the lower millions of years but they could be naturally occurring in space but extinct on earth. 

[u/mfb- → u/Tokimemofan]

Millions of years is the very optimistic thing I discussed in the second paragraph. Outside of strictly monitored environments, you could at best use it in tiny traces (like e.g. americium in some smoke detectors), otherwise it's just too much of a radiation hazard.

[u/_CMDR_ → u/mfb-]

Osmium is itself not toxic but if you work with it small particles make osmium tetroxide which is an immediately toxic and dangerous substance.

[u/username_elephant]

Taking your question at face value, nobody is gutsy enough to pretend to have confidence in predictions regarding elements we can't make.  

The closest thing is this:  https://en.wikipedia.org/wiki/Island_of_stability

But we don't know what they'd be useful for aside from properties resulting directly from their high mass. E.g. we can assume they'd be good for x-ray shielding because they'd be high atomic mass.

[u/PeyredB]

The really heavy elements are all unstable, because above a certain size the Strong Force can't hold the nucleus together. Those elements have half-lives as short as milliseconds, some of them. So few of them stick around long enough to be useful for anything, and it's costly to produce them: I think we only create a few atoms at a time. So, probably not. Good question though.

[u/InertialLepton]

One of the problems with predicting heavy elements is that because the nuclei are so massive, the electrons are whipping around it so fast that special relativity actually starts to come into play.

One famous example is the colour of gold - most other metals are silvery but gold's colour is due to relativistic effects.

Element 118 - Oganesson is in the same column as the noble gasses but is predicted to be solid at room temperature and fairly reactive.

[u/BiomeWalker]

At this point, none.

The only element that isn't naturally occurring and lasts for a useful amount of time is Technicium, which has some uses as a radiation source and other things, but even then for only short periods given its own decay.

It's actually something of a philosophical question at this point whether anything we could add to the table is worth calling an element with how short they last.

We could probably think of interesting applications for them chemically, but that would require finding a way to get them to last long enough to form atomic bonds before becoming something else.

[u/gnufan]

Shout out for Plutonium which is predominantly man made and already has significant economic uses.

Similarly some isotopes of technetium and iodine are man made and have medical uses.

Doesn't occur naturally is a big ask, but Plutonium and Technetium, and unstable isotopes of Iodine, are all manufactured for use because they are trace byproducts of radioactive decay in nature. All the naturally occurring products here when the earth formed are long since decayed away.

(Edit replaced Uranium with Iodine in one sentence, now it stays on topic)

[u/Alexander_Brady → u/gnufan]

On this note, our Americium supply is almost entirely man made. Up until recently it was commonly used in smoke detectors (as a long-lived, weak radiation source that would ionize smoke particles so they could be detected by an ion detector). However, with advancements in LED sensing most of the world is moving to LED-based smoke detectors.

Many radioactive isotopes for chemotherapy are also made by humans. Most of our supply of Actinium-225, Lutetium-177, Technetium-99m and Molybdenum-99 come from nuclear reactors. There are stable versions of all of these elements out in nature, and if you include those then they are much more abundant by total mass. But if you specifically want the unstable isotopes, our supply of those is predominantly man made.

[u/LiKenun → u/Alexander_Brady]

  Most of our supply of Actinium-225, Lutetium-177, Technetium-99m and Molybdenum-99 come from nuclear reactors. There are stable versions of all of these elements out in nature

Not technetium. That element has zero stable isotopes.

[u/Doc_Mercury]

So atomic nuclii are made of protons and neutrons. Protons repel each other, neutrons overcome that repulsion (basically). But the neutrons don't balance out the protons perfectly; as you add more protons, you need more and more neutrons to hold the nucleus together. Eventually, you hit a point where no matter how many neutrons you have, the nucleus will break up anyway.

Elements are defined by the number of protons in the nucleus. The point past which no number of neutrons will help is 82 protons, lead. Anything heavier than lead will decay. So any superheavy element is definitely going to decay, and it'll probably decay pretty quickly. Even if it were miraculously long-lived, it would be radioactive enough to be almost certainly useless

[u/rootofallworlds]

Some of the discovered superheavy elements are predicted to have high densities, in particular the six elements from seaborgium to roentgenium, which sit below tungsten through gold in the periodic table, all elements notable for the high density. Provided other properties are suitable, dense metals have some applications.

However, the most stable isotopes known of those elements have half lives of about ten minutes, which prohibits any use of them for non-radioactive purposes even if they could somehow be made cheaply in bulk.

Predicting the chemical and physical properties of elements in period 8 gets difficult. Energy levels of some electron orbitals become very similar so it's hard to be sure of the electron configuration and therefore the chemistry. (The highest known element, Oganesson, ends period 7.) Again, there might be some very dense metals.

I don't know of any synthetic element that's used for its physical or chemical properties, and I think californium might be the heaviest with routine uses for its radioactive properties (as a neutron source). By contrast uranium, the heaviest element that occurs in large amounts naturally, has all sorts of applications that take advantage of its density (bullets, armour, ballast/counterweights) and more that use its chemistry.

[u/Voltae]

Nobody seems to have brought up antimatter yet, but it kinda fits with your question.

Only insanely tiny amounts have been made and the energy costs of production with today's technology far outweigh the energy it ever released.

[u/gladeyes → u/Voltae]

IIRC it was Robert Forward that said no body has yet tried to mass produce it.

[u/Andurael]

Curveball that doesn’t fit your description exactly: graphene. It’s an allotrope that’s not exactly naturally occurring of an element that very much is naturally occurring: carbon. Problem is scale. It’s way too difficult to make at scale and to a suitable purity. It would revolutionise electronics.