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What's the chance that there might be undiscovered chemical elements in the Solar System - either on planets or around the Sun or on asteroids of the Oort-cloud?

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    $\begingroup$ If you mean elements with atomic number higher that 115-ish then of course there is a chance, so far nothing prohibits atoms from having as many protons - though stability is an issue. But I don't see the point in asking 'What is the chance..?' $\endgroup$
    – harogaston
    Commented Jul 5, 2014 at 18:59
  • $\begingroup$ Likelihood is "maybe": Superheavy Element 117 Points to Fabled “Island of Stability” on Periodic Table scientificamerican.com/article/… $\endgroup$ Commented Jul 9, 2014 at 21:56
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    $\begingroup$ Of course there will be such elements rather briefly, every time a high energy cosmic ray runs into something. They may not last for more than a few picosecond though. $\endgroup$ Commented Jul 23, 2019 at 13:58

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As far as elements (e.g. on the periodic table) go, I would say the odds are very slim. We already discovered or produced all the elements of the Periodic Table up to atomic number 112 at least. As the number increases, the half lives of the elements generally decreases, and is very short for elements above 102. If this trend holds true as the number increases, practically all the "undiscovered" elements should have turned into the lower known atomic number elements.

However, there is hope. There is a theorized "island of stability" where a narrow range of yet to be discovered high atomic number elements may be stable: http://en.wikipedia.org/wiki/Island_of_stability I would say there is a slight chance this element could be discovered in the solar system.

Edit

There is new news Phys.org (October 2023) of an Asteroid 33 Polyhymnia, which is reported to have a density greater than that which could be explained by the known elements of the periodic table. It claims that there are likely higher number elements (e.g. from the island of stability) in the asteroid. My thoughts are (most likely first):

  1. The measurements are wrong. Edit: James K points out in the comments below that this is most likely the case.
  2. There is perhaps some mineral that is denser than material made of a single element present.
  3. There are indeed elements from the island of stability in it.
  4. Perhaps it contains something exotic: such as dark matter, neutronium, strange matter, etc.

My thoughts are we should explore this further. First, verify the measurements, then send a mission / probe to explore! It would seem some of this material would have fallen to Earth, perhaps we can check for it in existing meteorite samples, and samples from asteroid impacts.

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    $\begingroup$ Elements in the "island of stability" are expected to be relatively stable, compared to their neighbors. Quoting the Wikipedia article, "Specifically, they are expected to have radioactive decay half-lives of minutes or days, with "some optimists" expecting half-lives of millions of years." Even with half lives in the millions of years, there could still have gone through hundreds or thousands of half-lives over the history of the Solar System. Unless the optimists are underestimating their stability, there should be practically nothing left of them. $\endgroup$ Commented Jul 7, 2014 at 23:57
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    $\begingroup$ I think the possibility of an asteroid consisting of superheavy elements found nowhere else (why?) is roughly zero. The article the story links to is about what would be the density of such a material, not an article that claims to measure the density of the asteroid. I think you should include a reference to a refereed paper that says the density of the asteroid is anomalously large. $\endgroup$
    – ProfRob
    Commented Oct 17, 2023 at 15:20
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    $\begingroup$ The source for the density is arxiv.org/abs/1203.4336 see also astro.kretlow.de/simda/show/The author indicates that the published value is unrealistic and shouldn't be used to infer anything about the asteroid. $\endgroup$
    – James K
    Commented Oct 17, 2023 at 21:06
  • $\begingroup$ @James K - Thank you for the information, this points more toward my most likely thought, that the density of the asteroid is measured wrong. $\endgroup$
    – Jonathan
    Commented Oct 22, 2023 at 0:45
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Further to the answer of @Jonathan, the thing that distinguishes one chemical element from another is the number of protons in the nucleus, which in turn determines the number of orbital electrons in the uncharged atom.

But we already know the element that corresponds to any given number of protons between 1 and 112; that's the atomic number. And you can't have a fraction of a proton. The only room for possible new elements is on the end.

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A chemical element is defined by the number of protons it contains, this largely defines its chemical properties. Elements can, within certain bounds, have varying number of neutrons (elements with the same number of protons but a different number of neutrons are called isotopes). Number of neutrons can have a subtle effect on chemical properties and a more significant effect on stability ie rate of radioactive decay.

But the big chemical differences which define an element are determined by the proton number and a given element will only have a handful of isotopes within a fairy narrow range.

So, elements are classified by the periodic table which lists the elements in groups according to atomic number (number of protons). When the periodic table was first proposed there were a number of gaps between known elements (at this point the existence of protons was not known). These gaps have subsequently been filled so there is no space for new elements untill you get to high atomic numbers.

The periodic table is full in terms of what could be considered reasonably stable elements. There is no fundamental reason why you can't propose elements with ever increasing atomic numbers. However the trend so far is that with increasing atomic number elements become more and more unstable. They can be created in particle accelerators but only exist for a tiny amount of time and don't exist in nature in any way which you might consider being a 'real' material like iron or copper.

There have been various predictions of theoretical islands of stability but even then we are talking about very short lived elements.

So in terms of the way that we tend to understand the term there are no new elements to discover, as all reasonably stable possibilities are accounted for.

Having said that there could well be entirely new materials composed of known elements or indeed previously unknown states of matter.

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Another way to look at this question is to consider how elements are produced. The elements with larger atomic numbers (i.e.: 26 (iron) or so) on the periodic table are primarily produced during supernovae explosions. Based on a lot of findings in stellar physics and nuclear physics in the past half century, it's unlikely that a transfermionic element (an element with 92 or more protons) can be produced in that process. Further, these elements tend to decay with half lives measured in hours or minutes (or less), so even if they were produced in a supernova, they are long since gone.

As @Jonathan pointed out, there is some potential for such elements due to the so-called island of stability, but they are still likely to be highly unstable, with very short decay times.

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  • $\begingroup$ Iron is produced around the core of big stars by fusing silicon. The elements produced in supernovae are the ones heavier than iron. Just pointing :) $\endgroup$
    – Joan.bdm
    Commented Jul 3, 2014 at 7:22
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    $\begingroup$ Good point. However, some elements, europium for instance, are produced in the corona during a star's time on the main sequence. $\endgroup$
    – Ben
    Commented Jul 22, 2014 at 2:00
  • $\begingroup$ Didn't know that! I guess the millions Kelvin is the reason for that. Thanks Ben! $\endgroup$
    – Joan.bdm
    Commented Jul 22, 2014 at 6:18
  • $\begingroup$ @Ben Do you have a reference? Coronae seem not dense enough for fusion reactions and we would not expect fusion to produce elements that heavy. So what gives? $\endgroup$ Commented Oct 27, 2023 at 1:24
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Unknown elements seem unlikely, but other types of unknown materials may exist elsewhere. Following are a few such materials, which are calculated to be stable under physical and chemical conditions that are, well, out of this world:

  • Hydronium, $\text{H}_3\text{O}$ (not to be confused with the cation formed when acids dissolve in water), is reported to be stable under conditions existing in the interiors of Uranus and Neptune, making it a candidate material source for the peculiar magnetic fields of these planets. See Ref. 1.

  • Ammonium, $\text{NH}_4$, closely related to hydronium, has also been proposed as an interior component of Uranus and Neptune. Metallization of an ammonia-hydrogen mixture to form $\text{NH}_4$ occurs at relatively low pressuee compared with other nonmetallic materials, making its existence in the ice giants likely. See Stevenson[2].

  • Carbonic acid, $\text{H}_2\text{CO}_3$, may be found as a major species in some outer-planet moons, as this requires less extreme pressure than the metallized excess-hydrogen compounds described above. From Wikipedua:

Significant amounts of molecular $\text{H}_2\text{CO}_3$ exist in aqueous solutions subjected to pressures of multiple gigapascals (tens of thousands of atmospheres) in planetary interiors.[3][4] Pressures of 0.6–1.6 GPa at 100 K, and 0.75–1.75 GPa at 300 K are attained in the cores of large icy satellites such as Ganymede, Callisto, and Titan, where water and carbon dioxide are present.

References

  1. Peihao Huang, Hanyu Liu, Jian Lv, Quan Li, Chunhong Long, Yanchao Wang, Changfeng Chen, Russell J. Hemley and Yanming Ma (March 3, 2020). "Stability of H3O at extreme conditions and implications for the magnetic fields of Uranus and Neptune". Proc. Nat. Acad. Sci. 117 (11), 5638-5643. https://doi.org/10.1073/pnas.1921811117.

  2. Stevenson, D. (1975). "Does metallic ammonium exist?". Nature 258, 222–223. https://doi.org/10.1038/258222a0.

  3. Wang, Hongbo; Zeuschner, Janek; Eremets, Mikhail; Troyan, Ivan; Williams, Jonathon (27 January 2016). "Stable solid and aqueous H2CO3 from CO2 and H2O at high pressure and high temperature". Scientific Reports. 6 (1): 19902. Bibcode:2016NatSR...619902W. doi:10.1038/srep19902. PMC 4728613. PMID 26813580.

  4. Stolte, Nore; Pan, Ding (4 July 2019). "Large presence of carbonic acid in CO2-rich aqueous fluids under Earth's mantle conditions". The Journal of Physical Chemistry Letters. 10 (17): 5135–41. arXiv:1907.01833. doi:10.1021/acs.jpclett.9b01919. PMID 31411889. S2CID 195791860

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It is definitely possible, but in a very hot and active part of the universe. In order to discover these elements, there would have to be a lot of waiting for these elements to form. Our solar system isn't active enough, and a nebula would be the best place to look.

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  • $\begingroup$ our technology is not powerful enough to create it, and it isn't going to form if we just go there $\endgroup$ Commented Oct 30, 2018 at 20:37
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    $\begingroup$ This answer is completely wrong. Such elements cannot possibly be created in “nebulas” or even by stellar nucleosynthesis. Elements heavier than iron are only created in supernovae and the merger of neutron stars. $\endgroup$ Commented Oct 30, 2018 at 20:55
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    $\begingroup$ @Chappo I mostly agree with what you're saying, however, the s-process of neutron capture also produces a substantial amount of elements heavier than iron, and that mostly occurs in AGB stars. $\endgroup$
    – PM 2Ring
    Commented Nov 2, 2018 at 11:21
  • $\begingroup$ @PM2Ring Thanks for the comment (and link), I hadn't been aware of this source of heavier elements. $\endgroup$ Commented Nov 2, 2018 at 11:37

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