Naked Science Forum
Non Life Sciences => Chemistry => Topic started by: physicist_in_the_making on 17/10/2013 23:31:44
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Ive been wondering recently, what happens if a shell in an atom is forcefully overloaded with electrons?
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Dear physicist in the making - I abandoned any attempt at physics many decades ago, but my scanty knowledge of chemistry is that this is simply not possible. Electron shells can accommodate no more than there maximum number of electrons. This is an absolute. There is no mechanism that would allow it. I think the Pauli Exclusion Principle comes in to play in this regard, since it prohibits electrons from occupying the same quantum state. I suspect that if it was possible to undermine this principle then quantum mechanics would 'fall apart'. Since QM is remarkably well-validated this seems unlikely.
I repeat my caveat - this is a field in which I am too old to be a neophyte and too ignorant to be taken too seriously.
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Ophiolite is right. If you try to add extra electrons to an atom, the extra electrons will automatically move to occupy orbitals that can accept them (or if none are available, then to move to higher orbitals that are unoccupied).
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This is an absolute
I am no physicist, nor chemist (Yet) But I would say science has no absolutes, only near absolutes.
No?
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One thing to keep in mind is that the bohr diagrams with cute circles and shells don't represent the true form of atoms.
I'm not quite sure of the current theories of atoms and electrons, but whatever it is that creates pairing of electrons may preclude triplets. And a "shell" is comprised of specific orbitals of which one can't just add an extra half orbital once it is full.
Perhaps rather than considering "shells", one should think of energy minima with specific orbital configurations.
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If you add an electron to an atom you get a negative ion. Where it resides depends on the filling of existing shells or orbitals, but you can't overfill an orbital - the additional electron has to go into the next available orbital.
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This is an absolute
I am no physicist, nor chemist (Yet) But I would say science has no absolutes, only near absolutes.
No?
You are correct, but the sentence is used in the context of the Pauli Exclusion principle. If this is shown to be false in some circumstances then the absolute nature of this statement would be false. I could definitely have made that clearer in the way in which I phrased my post. Or put another way, there is an implicit If...then... statement. My impression is that there are a lot of these in science, some of which would be better made explicit.
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We can extend this answer from single atoms to larger objects like gold nanocrystals, the CPU chip in your computer, the Golden Gate bridge or the superconducting magnets in the MRI machine at your local hospital.
In these environments, there are many atoms of the same kind (whether Gold, Silicon, Iron or Niobium, respectively), at roughly the same temperature, and so electrons in many atoms will tend to fall into the same orbitals.
However, these atoms are in close proximity, and the Pauli Exclusion Principle forbids two electrons (or in general, two Fermions (http://en.wikipedia.org/wiki/Fermion)) sharing the same energy level. In this case, the orbital does not have a specific energy level, but expands out to a band of energies (http://en.wikipedia.org/wiki/Electronic_band_structure).
I understand that this effect can also be seen in less-dense states of matter, such as gases (http://en.wikipedia.org/wiki/Spectral_line#Pressure_broadening).
One effect that occurs in a superconductor is that the electrons "pair-up", so that they no longer act as Fermions, but effectively act as composite Bosons (http://en.wikipedia.org/wiki/Cooper_pairs), and these can all have the same energy level. This occurs in the cryogenic environment of the MRI machine.