Does an electron's energy state affect its distance from the nucleus?

[Latsabb]

Ok, so what I considered to be true for quite some time now has been somewhat tarnished after something that was said recently in a lecture, so I am looking for some insight.

Basically, I was told several times by several teachers/professors over the years that when an electron absorbs a photon, and moves to a higher energy state, the distance between the electron and the nucleus increases. (Obviously there is a probability, and I know of the electron cloud and such, but basically the higher energy state makes it more likely that the electron is further out) This was then used to demonstrate that at a high enough energy state, the electron would be "shot" out, and become a free electron, and the atom would become ionized. The logic being that the energy added by the photon was so high that the distance between the nucleus and electron was too great for the nucleus to "pull it back in." (again, we are talking figuratively) This was also used to show why heavier elements were typically easier to rip electrons from, as the valence shell was much further away from the nucleus.

Now then, fast forward to the last week. It was stated that the electron was not capable of physical movement, and although the electron could be anywhere in the cloud, the probability was rather fixed into set orbitals. When I inquired about the above statement, it was flat out said that the increase in energy does not change the charge of the electron, so would not change the distance, and that a change in charge that WOULD change the distance, would have an acceleration and therefore a movement, which wasnt possible.

So now I am quite confused on which is actually correct. Thanks in advance to anyone that can help with this, as it has sort of messed with my head, being that something I "knew" for a long time might actually be very false.

 

[Ygggdrasil]

Basically, I was told several times by several teachers/professors over the years that when an electron absorbs a photon, and moves to a higher energy state, the distance between the electron and the nucleus increases. (Obviously there is a probability, and I know of the electron cloud and such, but basically the higher energy state makes it more likely that the electron is further out) This was then used to demonstrate that at a high enough energy state, the electron would be "shot" out, and become a free electron, and the atom would become ionized. The logic being that the energy added by the photon was so high that the distance between the nucleus and electron was too great for the nucleus to "pull it back in." (again, we are talking figuratively) This was also used to show why heavier elements were typically easier to rip electrons from, as the valence shell was much further away from the nucleus.

This is the correct view of things. For example, on the graph at the bottom of this page, you can see the probability of finding the electron a certain distance r away from the nucleus Pnl(r) for the various orbitals. As you can see, the electron, on average, is farther from the nucleus for orbitals with higher energies. This must intuitively be true because as you move two oppositely charged objects farther apart, you increase their potential energy.

I have no idea what the person who offered the second explanation was trying to say, but it makes no sense to me.

 

[Latsabb]

Their point didnt make much sense to anyone, but they were basically looking at it from a charge point of view. Someone else mentioned that the charge hadnt changed, just the energy, and that an increase in charge would have actually pulled them closer. But I guess their point was something about how to move further away, the electron would have to move, meaning an application of a force, and therefore an acceleration. He stated that no such acceleration was possible for an orbiting electron, and that all movements within the cloud were instantaneous. (ie. without acceleration)

 

[cgk]

Many experts in quantum mechanics would not agree with the statement that electrons do not move; they clearly have non-vanishing kinetic energy, and there even are interpretation of quantum mechanics (e.g. Bohm mechanics) which are experimentally indistinguishable from mainstream-interpretations, and in which they do fly around like classical billard balls.
Also, whether or not the electronic transition upon absorption of a photon happens instantaneous is a non-trivial question which cannot be answered in the context of vanilla molecular quantum mechanics (without QED), where the eletromagnetic field is treated classically. This process is simply not within the realm of the model you are working in.

But, anyway, neither of these two aspects has not much to do with electrons being farther away from the nucleus or not. The different orbitals clearly have different <r^n> expectation values, with valence electrons being much further away from the core. Your first explanation fits to this. This has nothing to do with the charge of electrons changing, and I cannot see how anyone would think that. Claiming that is like saying that you need to change your own body mass in order to climb up a large building in an elevator.

 

[LudusRex]

I can provide some insight into this question. The relationship between an electron's energy state and its distance from the nucleus is a complex one and is still an area of active research in the field of quantum mechanics.

Firstly, it is important to understand that an electron does not have a fixed position or orbit around the nucleus. Instead, it exists in a cloud of probability known as the electron cloud. This means that the electron can be found anywhere within this cloud, with varying levels of probability.

When an electron absorbs a photon and moves to a higher energy state, its probability distribution within the electron cloud changes. This means that there is a higher chance of finding the electron further away from the nucleus. However, this does not necessarily mean that the distance between the electron and the nucleus physically increases.

The concept of "shooting out" or becoming a free electron is not entirely accurate. Instead, when an electron is ionized, it is simply removed from the atom's electron cloud. This can happen at any energy state, not just at a high energy state.

Regarding the statement that the electron is not capable of physical movement, this is not entirely true. According to quantum mechanics, the electron can exist in multiple energy states simultaneously. However, its energy state can only change through interactions with other particles or fields. This change in energy state does not necessarily mean that the electron is moving in a physical sense.

In summary, an electron's energy state does affect its distance from the nucleus, in terms of probability. However, this does not necessarily mean that the physical distance between the electron and nucleus changes. The concept of an electron's charge and its effect on distance is also a complex topic and is still an area of ongoing research. I hope this helps to clarify some of your confusion.