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Author: Subject: Why are odd elements rarer that even elements ?
metalresearcher
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[*] posted on 18-10-2020 at 12:05
Why are odd elements rarer that even elements ?


On this image on Wikipedia, I noticed that almist *all* odd elements are considerably rarer than even ones.

https://commons.wikimedia.org/wiki/File:Elements_abundance-b...

Except Beryllium (4, even) is very rare, even compared to the odd neighbors Lithium (3) and Boron (5).
Another issue : these two elements are also rare compared to other elements of the second row.

Why ?
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[*] posted on 18-10-2020 at 12:19


I know that elements 3, 4, and 5 are rare because they are not created in stellar cores. Fusion goes H -> He -> C, and skips right over those three.
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EthidiumBromide
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[*] posted on 18-10-2020 at 12:20


I'm not sure if I'm entirely correct on this, but I recall that it's a general trend that nuclei with odd numbers of protons tend to be less stable.
This is evidenced by certain facts, such as monoisotopic elements (elements with only one stable isotope) are exclusively odd-numbered elements (one exception: beryllium), and odd numbered elements generally have less stable isotopes that even numbered elements. And the formation of odd numbered elements by fusion within stars is also a rarer event than the formation of even-numbered elements.

Perhaps someone else will come along and provide more concrete and reliable information. I don't know the explanation of this phenomenon as physics is not my strong side. But if anything, maybe it could guide you in the right direction for researching this subject.

[Edited on 18-10-2020 by EthidiumBromide]
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DraconicAcid
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[*] posted on 18-10-2020 at 12:50


I have a vague feeling that this could probably be explained by the existence of nuclear orbitals, but I've never looked into nuclear physics deeply enough to know more about these orbitals than that they exist.

(Although I get the feeling that a joker will be along to explain it in terms of radical pathways soon enough.)




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clearly_not_atara
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[*] posted on 18-10-2020 at 13:07


Nucleons in nuclei pair up in spin up/down pairs similarly to electrons in orbitals (because they're fermions). So the most stable nuclei usually have even numbers of nucleons, and with the exception of lithium-6, boron-10 and nitrogen-14, it is basically always more stable to have an even number of protons with an even number of neutrons than a maybe more favorable proton/neutron ratio with odd numbers of both.

As such e.g. sodium-22 decays to neon and aluminium-26 decays to magnesium while magnesium-24 and silicon-28 are stable. A nucleus with an odd number of protons is generally only stable with an even number of neutrons and also a favorable proton:neutron ratio. Iron has four stable isotopes, cobalt one, nickel five and copper two, et cetera.




[Edited on 04-20-1969 by clearly_not_atara]
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Maurice VD 37
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[*] posted on 19-10-2020 at 03:41


On the other hand, Beryllium-8 is so unstable, that it does not exist longer than the duration of the collision between two alpha particles (helions). Why is it so ? Beryllium-8 has an even number of protons and neutrons, and even a doubly even number of protons and neutrons. It must be super stable. And still it does not exist. Why ?
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[*] posted on 19-10-2020 at 22:51


Quote: Originally posted by clearly_not_atara  
Nucleons in nuclei pair up in spin up/down pairs similarly to electrons in orbitals (because they're fermions). So the most stable nuclei usually have even numbers of nucleons, and with the exception of lithium-6, boron-10 and nitrogen-14, it is basically always more stable to have an even number of protons with an even number of neutrons than a maybe more favorable proton/neutron ratio with odd numbers of both.

And hydrogen-2.
Of the other natural odd-odd nuclei, Ta-180 does not decay at all, V-50 very slowly and La-138, Lu-176 and K-40 slowly.
Be-8 is unstable not because it is particularly unstable but because He-4 is super stable. For the same reason there is no bound nucleus with mass 5.
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Mateo_swe
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[*] posted on 20-10-2020 at 07:48


Cant this be related to the electron shells?
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DraconicAcid
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[*] posted on 20-10-2020 at 08:26


Quote: Originally posted by Mateo_swe  
Cant this be related to the electron shells?

The nucleons do exist in shells, which are similar to the electron shells, but unrelated.




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