Naked Science Forum
Non Life Sciences => Chemistry => Topic started by: thedoc on 27/09/2016 09:53:02
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Luke Pullar asked the Naked Scientists:
It seems odd that new elements can be created and added to the periodic table even though they decay in a vanishingly small increment of time. They're not useful in any way, and they cannot exist outside of a minuscule fraction of a second under laboratory conditions. Why add them?
What do you think?
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You could say the same about the Olympics. Someone ran (or swam or jumped) a teeny bit better than someone else. It's not useful in any way, and it doesn't exist outside the Olympic stadium. Why give them a gold medal??
It's mostly human competitiveness - my particle accelerator (or gamma ray spectrometer or biceps) are bigger than yours...
But there is some use in it - there is some debate about the energy levels inside a nucleus, and how many protons and neutrons will fill an energy shell. This affects the energy of the nucleus and its lifetime. There is a hypothesis that if you could create an atom with a filled shell of both protons and neutrons, it might be exceptionally stable (https://en.wikipedia.org/wiki/Island_of_stability).
In theory, some such atoms could be left behind on Earth after a neutron star collision, but careful searches have failed to find any. So people are trying to make them in the lab.
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Luke Pullar asked the Naked Scientists:
It seems odd that new elements can be created and added to the periodic table even though they decay in a vanishingly small increment of time. They're not useful in any way, and they cannot exist outside of a minuscule fraction of a second under laboratory conditions. Why add them?
What do you think?
Years back universal scientists declared that the earths proximity to the sun, causes the higher elements to become unstable. Even when cooled the radiation that passes right through the earth, is just too much for those larger elements to deal with. They are too unstable to positively identify. Scientists from different areas of earth testing these substances found that they could not get similar results. That is when they declared them too unstable to be safely used. Back then radiation that was detectable was considered slow moving or not at natural undetectable normal super high velocity ambient radiation.
The universal scientists stopped declaring elements at Uranium. They declared the rest radio active isotopes. Because crazy fools ran the world and the dark ages were announced, most never understood how important it is to keep radio active materials from getting into everything.
Sincerely,
William McCormick
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I heard an interview with a researcher who was studying Nobelium.
It's half-life is around 2.5 seconds, and they can produce about 10 atoms per second.
They were using lasers to study the electron energy levels. Apparently, the intense electric fields around these very positive nuclei are expected to produce some unusual electron behaviors which are not seen with lighter elements.
See: http://www.nature.com/nature/journal/vaop/ncurrent/full/nature19345.html
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Do these new "elements" which last only for seconds or microseconds, exist anywhere else in the Universe, except in laboratories on Earth?
If not, I agree with Luke, they're not real "elements" at all. Just something we've fiddled about with, and cooked up locally. Surely the fact that they disappear so quickly, rules them out as real elements. How can something that vanishes in a split-second, be regarded as anything more than a terrestrial artefact.
Shouldn't a real element stay around for the duration of the Universe, so that it could always be found in the Universe, without relying on a terrestrial source?
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Do these new "elements" which last only for seconds or microseconds, exist anywhere else in the Universe, except in laboratories on Earth?
If not, I agree with Luke, they're not real "elements" at all. Just something we've fiddled about with, and cooked up locally. Surely the fact that they disappear so quickly, rules them out as real elements. How can something that vanishes in a split-second, be regarded as anything more than a terrestrial artefact.
Shouldn't a real element stay around for the duration of the Universe, so that it could always be found in the Universe, without relying on a terrestrial source?
Many "Natural" elements do not have infinite lifetimes. Carbon 14 is constantly forming being formed in our atmosphere and decaying, Uranium is also a "naturally" occurring element which decays, and in doing so creates other short-lived elements. I don't think it makes much sense to say that naturally occurring Radium is not a "real element" just because its most stable isotope has a half-life of just 1600 years.
As far as these other element existing elsewhere in the universe, If we can make them here on the Earth, then surely they are formed in the supernovae that forged all the other elements including the Uranium we still find in our own crust.
That's one reason for trying to make these elements on Earth; to learn the rules that determine just what is possible in terms of element formation and to verify whether or not our understanding of what these rules are stand up to experiment.
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Do these new "elements" which last only for seconds or microseconds, exist anywhere else in the Universe, except in laboratories on Earth?
If not, I agree with Luke, they're not real "elements" at all. Just something we've fiddled about with, and cooked up locally. Surely the fact that they disappear so quickly, rules them out as real elements. How can something that vanishes in a split-second, be regarded as anything more than a terrestrial artefact.
Shouldn't a real element stay around for the duration of the Universe, so that it could always be found in the Universe, without relying on a terrestrial source?
It is not obvious to me why natural occurrence is necessary for something to be an element. We can synthesize molecules that have never before existed anywhere in the universe, but that doesn't mean that they aren't molecules (some of these are also delicate, and decompose quickly.)
Certainly there is something less "fundamental" about elements that exist only on Earth, but these synthetic atoms have unique numbers of protons and neutrons, and are therefore new elements.
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Do these new "elements" which last only for seconds or microseconds, exist anywhere else in the Universe, except in laboratories on Earth?
Supernovas are thought to cast elements up to iron and cobalt into space.
- Measurement of the light output of supernovas shows a reduction in intensity over time which is related to the radioactive decay of Cobalt 56 (half-life: 77 days).
- Trace amounts of Iron 60 are found on Earth. With a half life of around 2.6 million years, it is thought that this must have originated in a supernova that occurred in the vicinity of the Sun
- Elements much heavier than iron, like gold, uranium and Nobelium are though to be cast into space during the collision of neutron stars. Nobelium doesn't last very long, but the gold is a valuable commodity on Earth.
Shouldn't a real element stay around for the duration of the Universe, so that it could always be found in the Universe, without relying on a terrestrial source?
It is thought that elements produced in the big bang included Hydrogen, Helium and trace amounts of Lithium.
All the rest have not been around for the age of the universe, but were formed in later stars, supernovas, neutron star collisions and physics labs.
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Thanks to evan, janus and chiral for all your valuable comments.
The point that "heavy" elements are always getting created in supernovae, is one that I realised with a head-smack after posting. But I didn't to bother to edit, as it was obviously bound to get picked up.
However, going back to the original question, about whether very transient, swiftly-decaying elements should be added to the Periodic Table. I would say not, because it would make the list of "elements" too long.
If I might cite a comparable example from Astronomy. The list of "planets" in the Solar System was eight, until the year 1930. In that year, a new "planet", Pluto, was discovered. Right from the time of its discovery, there were doubts whether "Pluto", should properly be added as a planet, as it's very small. However it got accepted until 2006, when the IAU threw it out.
This was because a lot of new objects were being discovered, like Eris, which is bigger than Pluto. So if you accept Pluto as a planet, you'd have to accept Eris too. And there were more objects of comparable size. You could eventually end up with a list of 40 or 50 "planets". Which is far too long.
So the IAU demoted Pluto to dwarf status. Now astronomers (well, most of them), only acknowledge eight planets on the list. Pluto and the rest are regarded as interesting, but not genuine.
Couldn't this approach be adopted with the Periodic list of elements? That's to say, physicists and chemists, should only recognise 92 genuine elements, the rest being merely interesting?
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Thanks to evan, janus and chiral for all your valuable comments.
The point that "heavy" elements are always getting created in supernovae, is one that I realised with a head-smack after posting. But I didn't to bother to edit, as it was obviously bound to get picked up.
However, going back to the original question, about whether very transient, swiftly-decaying elements should be added to the Periodic Table. I would say not, because it would make the list of "elements" too long.
If I might cite a comparable example from Astronomy. The list of "planets" in the Solar System was eight, until the year 1930. In that year, a new "planet", Pluto, was discovered. Right from the time of its discovery, there were doubts whether "Pluto", should properly be added as a planet, as it's very small. However it got accepted until 2006, when the IAU threw it out.
This was because a lot of new objects were being discovered, like Eris, which is bigger than Pluto. So if you accept Pluto as a planet, you'd have to accept Eris too. And there were more objects of comparable size. You could eventually end up with a list of 40 or 50 "planets". Which is far too long.
So the IAU demoted Pluto to dwarf status. Now astronomers (well, most of them), only acknowledge eight planets on the list. Pluto and the rest are regarded as interesting, but not genuine.
Couldn't this approach be adopted with the Periodic list of elements? That's to say, physicists and chemists, should only recognise 92 genuine elements, the rest being merely interesting?
Because half-life doesn't make a good parameter by which to judge whether something is an element or not. With Pluto, we didn't have a clear cut definition for what a planet was until the IAU decided on the most recent definition.
We do have a good definition for element.
Besides, using half-life would not be consistent with a cut off at element 92. Neptunium, Plutonium, and Americium all have Isotopes with half-lives that are longer than the longest lived isotopes of a number of elements with atomic numbers less than 92, the shortest being Americium at 7270 yrs. Compare this to Actinium, Radium, Francium, Radon, astatine and Polonium, The longest lived isotope in this group belongs to Radium at 1600 yrs, and the longest lived isotope of Francium (atomic number 87) is a mere 22 min.
Why include it as a "real" element while rejecting higher numbered elements with more stable isotopes?
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OK Janus, many thanks for your post - you've (almost) persuaded me.
Especially when you cite Francium, whose longest-lasting isotope , -223, has a half-life of only 22 minutes! That did surprise me. Is there much Francium in the Universe?
But if it's accepted as an entry in the Periodic Table, then I suppose there's not much more to say.
Except I still feel that "elements" with a far shorter half-life, measured in mere milliseconds, don't really belong in a practical Periodic Table.
Thanks again for your post, which I appreciate.
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Let us also not forget Technetium, which is smack dab in the middles of the periodic table. There are no stable isotopes, and the longest lived has a half life of 4 million years (other isotopes have half lives in the days to weeks range, and some decay even more swiftly). https://en.wikipedia.org/wiki/Technetium
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Now, there are some "exotic" elements that I am unsure of whether to include or not. These are atoms that contain particles other than protons, neutrons and electrons (sometime in addition to these standard particles, sometimes without any). Many examples include muons substituted for electrons. These decay after only a few microseconds, but that is an eternity for some physical processes that occur on the atomic scale (for instance we can do spectroscopy on these to measure the energy levels, and this is even a tactic for performing "cold" fusion).
https://en.wikipedia.org/wiki/Exotic_atom
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Let us also not forget Technetium, which is smack dab in the middles of the periodic table. There are no stable isotopes, and the longest lived has a half life of 4 million years (other isotopes have half lives in the days to weeks range, and some decay even more swiftly). https://en.wikipedia.org/wiki/Technetium
Promethium is similar. The longest lives isotope is 145Pm with a half life of about 18 years.
If we didn't put the radioactive elements in the table, it would have holes in it.
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How far could the Periodic Table be extended, if we allowed all possible combinations of protons, electrons and neutrons to be included?
Would it have hundreds of "elements"?
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If we define elements as atoms with unique numbers of protons, then there are already 118 known elements. If we include all isotopes (unique numbers of protons and neutrons), then there are already several hundred. unique nuclei known. I'm sure there are all kinds of crazy elements formed during catastrophic events involving neutron stars, even if they are only short-lived.
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If we define elements as atoms with unique numbers of protons, then there are already 118 known elements. If we include all isotopes (unique numbers of protons and neutrons), then there are already several hundred. unique nuclei known. I'm sure there are all kinds of crazy elements formed during catastrophic events involving neutron stars, even if they are only short-lived.
Thanks chiral, when you mention "crazy elements", I take it you're envisaging that such elements, even if short-lived and formed in catastrophic events, would still have nuclei containing only particles of "standard matter", ie protons and neutrons.
Might there be elements whose nuclei are made of particles of "Dark Matter". I mean, can Dark Matter form atoms, and "elements", which could be arranged into a kind of "Dark Matter Periodic Table".
Is there any way we can find out?
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Might there be elements whose nuclei are made of particles of "Dark Matter"?
That is a bit difficult to say, since we don't know what Dark Matter is!
Or, more accurately, it is definitely made up of a variety of different things, but we haven't positively identified the majority of it.
For example, the observed effects of Dark Matter has contributions from:
- Thinly-spread normal stars: These may have been ejected by galaxies during collisions, and be spread so thinly through space that they don't show up in astronomical telescopes behind the glow of Earth's atmosphere. These are made up of regular nuclei.
- Free-floating planets or the dark cinders of small burnt-out stars: These are made up of regular atoms, made of standard matter.
- Neutron stars: These are like a single huge nucleus, with the mass of the Sun
- Black holes: Our equations don't work at the center of a black hole. But it is safe to say that it can't form a stable nucleus, as it will swallow the rest of the nucleus.
- Relic Neutrinos from the Big Bang: These interact only with the weak nuclear force. They ignore the strong nuclear force that holds the nucleus together, so they can't form a stable part of a nucleus (and even if they did, they would be so light that they would not affect its properties in any measurable way). They can be emitted by normal matter during nuclear decay, and they can (infrequently) be absorbed or scattered by normal matter, making them (slightly) detectable. They even ignore the electromagnetic force that holds the atom together. Unbound, they fly straight through matter at enormous velocities.
- Unknown particles that don't even interact via the weak nuclear force (this is the theory that most particle physicists think is most likely at present): These would be even more ghostly than neutrinos, even less likely to form part of a nucleus with standard matter, and even less likely to be detected.
- Small deviations from Einstein's gravity on large scales (this theory is not very popular): This theory has no need for Dark Matter particles.
"Dark Matter Periodic Table"
If Dark Matter is primarily made of unknown/hard-to-detect particles (as many cosmologists expect), there is nothing preventing these (unknown) particles from experiencing an (unknown) 5th force which would bind them together in a periodic table of their own, forming the equivalent of a Dark Matter periodic table.
And if these unknown particles have antiparticles, they may annihilate, perhaps releasing energy in the form of gamma rays. Several searches of the gamma-ray spectrum are underway at present, in an attempt to detect such events.
See: https://en.wikipedia.org/wiki/Dark_matter#Composition
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Is not the reason for the hunt for elements with ever shorter lives the dream that past 118 there maybe at 126 "an island of stability" with a relatively long life and interesting properties.
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We don't add things to the periodic table; it's already there. We just make the things that are in it.
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Is not the reason for the hunt for elements with ever shorter lives the dream that past 118 there maybe at 126 "an island of stability" with a relatively long life and interesting properties.
Yes, and perhaps this "dream" as you call it, is a true intuitive reaction against the very idea of so-called "Dark Matter".
What if "Dark Matter" isn't some alien thing made of weird particles, but consists of ordinary proton/neutron elements in the "island of stability" - at 126, and possibly other "islands" beyond. Elements like these, would probably have long-lives and "interesting properties", as you say.
Such properties might account for observations such as anomalous galactic rotations. These are currently ascribed to the presence of "Dark Matter". Couldn't they be due to the presence of "super-heavy" elements which are higher in the Periodic Table than we've yet discovered?
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We don't add things to the periodic table; it's already there. We just make the things that are in it.
I salute you sir, as an apparent true "Aristotelian"! Aristotle said the very same thing - that the idea of a "table", is already there. It exists as an eternal, pure, thought-form : "tableness". All we do, when we make an actual dining-room table, is make the wooden bits, nails, glue etc, that are in it.
Mind you, you can't really be an Aristotelian if you're a chemist, as his chemical ideas about there being just "four elements" - Earth, Air, Fire and Water, are unsound.
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Is not the reason for the hunt for elements with ever shorter lives the dream that past 118 there maybe at 126 "an island of stability" with a relatively long life and interesting properties.
Yes, and perhaps this "dream" as you call it, is a true intuitive reaction against the very idea of so-called "Dark Matter".
What if "Dark Matter" isn't some alien thing made of weird particles, but consists of ordinary proton/neutron elements in the "island of stability" - at 126, and possibly other "islands" beyond. Elements like these, would probably have long-lives and "interesting properties", as you say.
Such properties might account for observations such as anomalous galactic rotations. These are currently ascribed to the presence of "Dark Matter". Couldn't they be due to the presence of "super-heavy" elements which are higher in the Periodic Table than we've yet discovered?
I think this is highly unlikely. Dark matter is invisible to the entire electromagnetic spectrum to the extent that we have probed it (between 10–12 and 103 meter wavelengths). Atomic or molecular matter made of such heavy atoms would surely absorb somewhere within this region. This apparent non-interaction with electromagnetic energy is why people have posited particles such as neutrinos as explanations of dark matter.
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Thanks chiral,. You say we've "probed" and found Dark Matter to be invisible in the electro-magnetic spectrum. Therefore it must be made of some exotic stuff, like neutrinos
I suppose Russian radar-operators could "probe" US B-2 stealth-bombers, find them to be invisible on radar, and report that B-2's therefore must be made of neutrinos.
But the B-2's are only made of metal, just shaped and coated in a way that absorbs and deflects the probing radar emissions, so the B-2's don't show up.
Perhaps "superheavy elements" have a similar effect when we try to probe them?
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We don't add things to the periodic table; it's already there. We just make the things that are in it.
I salute you sir, as an apparent true "Aristotelian"! Aristotle said the very same thing - that the idea of a "table", is already there. It exists as an eternal, pure, thought-form : "tableness". All we do, when we make an actual dining-room table, is make the wooden bits, nails, glue etc, that are in it.
Mind you, you can't really be an Aristotelian if you're a chemist, as his chemical ideas about there being just "four elements" - Earth, Air, Fire and Water, are unsound.
I'm not sure about Aristotle's periodic table.
More importantly, I'm not absolutely sure about mine.
Until the elements were synthesised and characterised by their chemistry, we were not sure of the "shape" of that bit of the periodic table.
It's not clear if we put the elements in their places.
Maybe, they put us in our place.
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Bored Chemist, once the idea of a "Table" of elements has got a grip on us, we have to make all the elements fit into it.
Even if they don't seem to, like "rare earths" and others, they must be forced in.
Quite rightly. Because the ideal of "Table", as Aristotle perceived long ago, is pure and perfect, and transcends the banal ugliness of physical reality. So we should follow the ideal, and put all the elements in their proper places.
At least you Chemists can do this, and deserve respect for it. Physicists want to do the same, but they've got very confused lately, and just run around frantically inventing new "particles" all the time.
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I don't think that the rare Earth elements (f block) had to be forced into the periodic table... They fit very nicely, that bit usually gets yanked out so that the dimensions of the table are closer to that of a page in a book or a poster. An extended version of the table can be found here:
https://upload.wikimedia.org/wikipedia/commons/thumb/2/22/32_column_PT.jpg/650px-32_column_PT.jpg
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I don't think that the rare Earth elements (f block) had to be forced into the periodic table... They fit very nicely, that bit usually gets yanked out so that the dimensions of the table are closer to that of a page in a book or a poster. An extended version of the table can be found here:
https://upload.wikimedia.org/wikipedia/commons/thumb/2/22/32_column_PT.jpg/650px-32_column_PT.jpg
Many thanks Chiral for the link, which I've carefully studied.
It displays the "Periodic Table" as a perfectly rectangular block, consisting of 7 horizontal rows, and 32 vertical columns. Like a page in a book or a poster, as you say.
And this, perhaps demonstrates strongly the point I alluded to earlier - that we intensely want to make the elements fit into an ideal geometrical "table".
However the "table" shown in your link isn't ideal at all. A lot of it is empty, blank squares, with no actual elements in them.
For example, consider the top row of the Table. This has the element "Hydrogen" at the far left. And "Helium" over at the far right. Between these two elements there's nothing but a row of empty squares.
How do you explain that?
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I don't think that the rare Earth elements (f block) had to be forced into the periodic table... They fit very nicely, that bit usually gets yanked out so that the dimensions of the table are closer to that of a page in a book or a poster. An extended version of the table can be found here:
https://upload.wikimedia.org/wikipedia/commons/thumb/2/22/32_column_PT.jpg/650px-32_column_PT.jpg
Many thanks Chiral for the link, which I've carefully studied.
It displays the "Periodic Table" as a perfectly rectangular block, consisting of 7 horizontal rows, and 32 vertical columns. Like a page in a book or a poster, as you say.
And this, perhaps demonstrates strongly the point I alluded to earlier - that we intensely want to make the elements fit into an ideal geometrical "table".
However the "table" shown in your link isn't ideal at all. A lot of it is empty, blank squares, with no actual elements in them.
For example, consider the top row of the Table. This has the element "Hydrogen" at the far left. And "Helium" over at the far right. Between these two elements there's nothing but a row of empty squares.
How do you explain that?
What's to explain?
You are claiming that we want it to be a rectangle. But that's not how we draw it- because it really isn't that shape.
So what we"want" (so you say) doesn't matter.
It's like saying that we want to draw the map of the US as a big rectangular grid, but there's Alaska stuck out on one side and Hawaii on the other - how do we explain that?
Well, we drew it the shape that reality dictates.
WTF else would we do?
Why do you believe that " we intensely want to make the elements fit into an ideal geometrical "table"."?
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I'm just pointing out that the "Table of Elements" in the link that you kindly provided, is a big rectangle with lots of holes in it.
Especially striking is the long line of holes, in the top row, between Hydrogen on the left, and Helium on the right.
These holes have absolutely no purpose except to fill out the top row, in order to make a rectangular "Table". That's why I think you want it.
I mean, do you think the top row of the "Table" implies that there actually are 30 "missing", as yet undiscovered, elements between Hydrogen and Helium?
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the element "Hydrogen" at the far left. And "Helium" over at the far right. Between these two elements there's nothing but a row of empty squares.How do you explain that?
The chemical properties of an element depend primarily on how many bonding electrons are in the outer shell.
Since the periodic table was developed by chemists, it's not surprising that they would want to classify elements according to their chemical properties.
- Helium has 0 bonding electrons, so it logically groups with Neon etc.
- Hydrogen can be considered to have 1 electron in it's outer shell, which sort of groups it with Sodium.
- But Hydrogen can also be considered to have room to hold 1 extra electron in its outer shell, which would group it with chlorine.
- So Hydrogen is a bit of a "floater"
There are some other organizations for the periodic table which try to represent these characteristics without any "gaps"; but some of them take up more than 2 dimensions!
See: https://en.wikipedia.org/wiki/Alternative_periodic_tables
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My theory for why elements higher than uranium are unstable comes down to the electron and nucleus orbital configurations. An atomic electron is a negative charge in motion; orbital shape. As such it creates both electrostatic and magnetic forces. The electrons of any given atom will repel each other using electro-static repulsion. However, the movement of the electrons, in the orbital will counter this with magnetic force attraction. In the case of oxide or O-2, oxygen can hold two more electrons than it has protons, due to the extra electron magnetic attraction, countering the extra electron repulsive force, that exists beyond the protons.
As such, it makes sense that the nucleus will use it own version of nuclear orbitals, to help create the needed magnetic force vectors to lower the impact of the positive charge repulsion between the protons; spin and circulation.
Based on the stability of atoms, although the electrons orbitals and the protons orbital will net attract due to their own internal magnetic attraction, the magnetic addition of the electron orbitals, to the protons orbitals, appear to add a net repulsive magnetic force, between the electrons and nucleus. This never allows the two to meet. The result are persistent atoms. It may well be that the nucleus and electron orbitals reflect each other, like chiral centers in chemistry, but they can't overlap in space.
When we make higher atoms than uranium, in the lab, both the electrons and protons are magnetically adding among birds of a feather. However, this is compounding the magnetic repulsion between the nucleus and electron cloud used for atomic persistence; beyond stability.
Since neutrons do not carry charge, but will bind to the protons, the motion of the protons encourages the motion of the neutrons, while the inertia of the neutrons, inhibits the motion of the protons. This is the wild card, which the electrons don't see. The result is the nucleus is a reflection of electron orbitals, but modified by the need to optimize the neutron-proton binding forces.
In unstable isotopes, the impact of more or less than optimized neutrons, on the nucleus orbitals, will cause strain on the N-P binding forces, as these try to reflect the electron orbitals. The result is decay.
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My theory for why elements higher than uranium are unstable comes down to the electron and nucleus orbital configurations.
Two points, firstly, you don't know what the word "Theory" means and secondly, if the electrons made a difference then changing the electron density near the nucleus would affect the half life.
In most cases it doesn't (electron capture is the obvious exception).
So the nuclear stability issue isn't down to the electrons.