Naked Science Forum
General Science => Question of the Week => Topic started by: Adam Murphy on 13/04/2021 14:51:52
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Mejnun got in touch to ask:
"I have learned at school that when an electron excites it jumps to another orbital around the nucleus. If an electron jumps an orbital you would expect that at that moment it can be found between the two orbitals. My teacher told me that this is never the case. I can not wrap my head around it. Does the particle just disappear in one orbital and appear in the other? Is this instant, is the particle in the other orbital the same? Can you please help me to understand this?"
Any thoughts?
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Simple answer:
Instead of thinking about orbitals as an electron's "location", think about them more as descriptors of the electron's "mood." Within a 1-atom system, all orbitals are centered at the nucleus, and there is a lot of spatial overlap between them. The real difference between the orbitals is not "where" they are, but rather "how" the electron is. Does it have a lot of kinetic energy? Does it have a lot of angular momentum (and if so, how is it oriented?). You might recognize these questions as related to the quantum numbers an electron can have, specifically the ones that determine orbital. And again, you'll note they don't say anything about "where" the electron is.
So think of the electron as a wasp. It can be calm, or it can be angry. There is nothing in between, and it can instantly go from one to the other or back.
Complicated answer: there is no spoon, it is only your mind that bends. (orbitals are made up tools that are useful for answering some questions, but not so useful for other questions... electronic states are even more complex models that are more accurate, and (for most people) even less intuitive.
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There has been considerable progress in the past decades with using lasers to stimulate and measure the quantum state of electrons around atoms.
- These techniques are expected to be the basis of the next generation of super-precise clocks (and maybe quantum computers?)
My simplistic understanding of some results I read is that the electron can be in a quantum superposition of two orbitals for a short period of time while it absorbs or emits a photon.
- The duration of the superposition corresponds to the uncertainty in time of absorbing or emitting the photon (as advised by Heisenberg and others)
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Mejnun got in touch to ask:
"I have learned at school that when an electron excites it jumps to another orbital around the nucleus. If an electron jumps an orbital you would expect that at that moment it can be found between the two orbitals. My teacher told me that this is never the case. I can not wrap my head around it. Does the particle just disappear in one orbital and appear in the other? Is this instant, is the particle in the other orbital the same? Can you please help me to understand this?"
Any thoughts?
Your teacher cannot, in general, be correct. The electron isn't owned by the nucleus, and it can travel between different nuclei. I'm pretty sure then it can be in between two electron states too, although the two states will inevitably have physical overlap and then the wavefunction will transition between them via the overlap if it has sufficient energy; nature will take the easiest route almost every time.
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The best pictorial representations of orbitals are fuzzy, because the describing function is a probability, not a locus. So although the probability of finding an electron "between orbitals" is very small, it isn't zero.
Thus even the most covalently bonded materials (e.g. low density polyethylene) have some free electrons and there is no perfect insulator.
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Hey there,
i think u have to first ask yourself, what does it mean for an electron to "be" somewhere? I've read this somewhere, which sums it up quite good:
Suppose I look at an electron, and see where it is, but what did I do when I 'looked' at the electron? I must have observed some photon that had just interacted with that electron. If I want to get an idea of the motion of the electron (no just its instantaneous momentum, but its position as a function of time), I need to observe it for a period of time. This is a problem, though, because I can only observe the electron every time it interacts with a photon that I can observe.
That's why I don't think we can exclude the idea of an electron being between orbitals, since tracking every motion is very hard.
And as the others already mentioned the electron is not necessarily bound, it can travel between nuclei.
I hope this helps your understanding.
Greetings.
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Thanks all - and the audio answer has just been published: https://www.thenakedscientists.com/podcasts/question-week/why-are-electrons-never-between-orbitals
chiralSPO - I particularly liked your analogy so it went into the script.