Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

I Do Electrons have different mass when in different orbitals?

  1. Jun 17, 2016 #1
    I am wondering do electrons have different mass when they are in different orbitals? I know the energy levels are different so it seems like they must have more mass at the lower orbitals. Has anyone ever tried to measure the mass of electrons in different orbitals?
  2. jcsd
  3. Jun 17, 2016 #2


    User Avatar

    Staff: Mentor

    I don't think you can separate individual electrons from the rest of the system (other electrons + nucleus) in order to perform a measurement on their mass. Not sure though.
  4. Jun 17, 2016 #3

    Vanadium 50

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor

    If different electrons had different masses they would be distinguishable, and that would dramatically change their physical and chemical properties.
  5. Jun 17, 2016 #4


    Staff: Mentor

    As mentioned above, the mass of an excited electron doesn't change, what changes is the mass of the atom, the system of both the electron and the nucleus.

    I don't know if this has been measured for partially excited states, but it can be measured for completely ionized hydrogen vs the ground state.
  6. Jun 17, 2016 #5


    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor
    2016 Award

    Have you tried solving the Hydrogen atom wavefunction (something we get undergraduate in physics to do in their QM classes)? You'll notice that the mass of the electron doesn't change for all the orbital solutions. And these solutions match extremely well with what we observe, especially from atomic spectra.

    So what can you conclude from that?

  7. Jun 17, 2016 #6


    User Avatar

    Different electrons ? ... :oldconfused:
    How about making this statement instead ?

    If electrons had different masses they would be distinguishable, and that would dramatically change their physical and chemical properties, which would make them ... different, I suppose ?

    Carry on...
    Last edited: Jun 18, 2016
  8. Jun 18, 2016 #7
    The change in the mass of the system composed of the nucleus and the electrons is a relativistic effect which is not included in textbook solutions of the hydrogen atom. The binding energy of the system composed of the nucleus and the electrons is ΔmC2 where Δm is the total mass loss of the system upon the formation of the bound state. The order of this binding energy is in the eV range.

    The analogue for the nucleus, the binding energy of the system composed of the neutrons and protons, is in the MeV range.

    The mass deficit in the bound system cannot be attributed to a single component of the system, it is a property of the whole bound system.

    I believe the nuclear analogue of this atomic phenomenon (which you describe as partial excitation) is easily measurable.
  9. Jun 18, 2016 #8


    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor
    2016 Award

    I am aware of such relativistic effects. However, this unfortunately might open another can of worms on the validity of the concept of "relativistic mass", which have had many previous threads before this (if you care to search). So whether one can accurately assign this as an increase in mass, or lump it into the relativistic momentum, is debatable. This is why I seldom (and lately, never) invoke such an effect.

    My asking first on whether the OP had done the solution to the hydrogen atom is to establish a "baseline knowledge" of what he/she already knows. If he/she hasn't done such a thing, then maybe it is a good place to start before we jump off into more complex situations. Otherwise, invoking such a thing as relativistic effect is trying to force an infant to run before he can even crawl. The fact that the OP posted this in the Classical Physics forum gave me a hint that we can't assume too much on the foundational knowledge.

    In any case, is THIS what the OP really is asking for, or is making a reference to?

  10. Jun 18, 2016 #9
    First of all I would like to thank everyone for their replies. I thought I would be lucky to get one or two replies. This was a great response. Thank you. To answer the general question of what level I am at. I am into natural philosophy so I do not have a strong background in mathematics. I am intensely interested in physics and how things work mechanically speaking. I am open to all perspectives but I do have my own opinions on how things in the Universe work. These statements should be a good clue to my style of thinking. I did look into the Bohr model already and found that this was abandoned as it did not work for more complicated atoms. I still think this method has great promise and can be applied to more complicated systems. What I believe is missing is that the equations need to evolve to more complex formulations in order to include additional interactions that effect the electrons and the overall atomic systems.

    I ask this question in order to see what the latest thinking is on this topic and because I have my own idea on what the answer should be. Ultimately I am interested in knowing and understanding the answer to this question. I was not able to find on the Internet a definitive answer to this topic.
    So far what I am getting from the comments is that the exact answer to this question is not known for sure. There are at least 3 various perspectives.

    1. No measurements have been made on individual electrons outside of an atom or at different orbitals.

    2. An assumption that if different electrons have different masses they would have different chemical and physical properties. I think that I may agree with that and so I suspect that electrons do have different properties when in different orbitals. This is what I think that I understand about electrons. Please correct me if I have something wrong.
    A. Electrons go to higher orbitals when they absorb photons.
    B. Electrons become more energetic as they absorb photons.
    C. Electrons can absorb more than one photon.
    D. Electrons loose energy when they emit photons.
    E. Electrons drop to lower orbitals when they emit photons.
    F. If Electrons gain and loose energy then their velocity and mass should change as a result of the energy gain or loss.

    My thinking that caused my question

    A. If photons do become more energetic when they absorb a photon then this must mean they have undergone a transformation because of the addition of the photon.
    B. If the photon does in fact increase in energy then the velocity at which the photon travels at must increase in that orbital. Has this ever been measured or looked for.
    C. Since I believe that a electron has a particular velocity then an electron has a path. At this point all Quantum Mechanics people may want to argue against such a notion as they believe that particles do not have individual paths or velocities. But in order to determine the possibility of electrons having different masses I think that a classical approach to this problem would be best suited for answering the question and or determining an experiment that could answer my question.
    D. I believe that classical approach would be the best approach since QM has provided no solution for the origin of mass so until such a time, I believe that QM mathematics could only be utilized to a limited extent by including QM constants and quantized values in differential equations.

    3. The next comment... "The change in the mass of the system composed of the nucleus and the electrons is a relativistic effect which is not included in textbook solutions of the hydrogen atom."

    That is very interesting, perhaps it should be included. What if the relativistic effect is in fact the complete and central cause of the emergence of the mass field. I think that this is a strong possibility. I believe that there is a great deal of evidence to support such a claim. Just my opinion.

    These additional comments hopefully explains why I am asking about such a specific detail. I want to know what main stream physics knows about my question. If someone knows the answer, for sure, one way or the other. I would really be interested in knowing the exact details and interpretation and meaning of those details. If someone knows of an experiment that has been performed to determine if electrons have different properties in different orbitals I would love to know the details of the results.

    Reference https://www.physicsforums.com/threa...erent-mass-when-in-different-orbitals.875885/
  11. Jun 18, 2016 #10
    I'm answering the original poster question by clarifying that exciting an electron to a higher energy level reduces the binding energy of the overall system made of the nucleus and electrons and as such increases the mass of the overall system but not the mass of the excited electron.
  12. Jun 18, 2016 #11


    User Avatar

    Staff: Mentor

    The problem with this way of thinking is that you already have an idea you want to shoehorn evidence to fit and you ignore evidence that goes against your idea, inventing excuses to cast doubt on the mainstream theories that cover this. This is a considerable cognitive bias and I implore you to think more on it.

    Let's be clear here. The theory that governs physics at this scale is Quantum Electrodynamics. As far as I know, QED states that you cannot distinguish the different electrons nor can you say that any particular electron inhabits a particular orbital. You can certainly perform a measurement and you will get a definite answer, but if you let the atom return to its previous state and perform the same measurement you cannot say that the electron you just measured was the same electron as before.

    Your first mistake is in thinking that the electron and the rest of the atom are separate systems. When a photon is incident on an atom and is absorbed, it is the atom as a whole that absorbs the energy of the photon, not a single electron. Remember that the electron interacts with the nucleus and the rest of the electrons, so if you do something to an electron it will affect the rest of the atom in some way. Exciting an electron to a higher orbital will subtly change the energy of the rest of the orbitals, as will ejecting an electron.

    Second, electrons themselves cannot have different chemical properties in different orbitals because the electrons are bound to atoms, and it is the atoms as a whole that have chemical properties.

    Third, it is the atom as a whole that gains or loses mass when absorbing or losing energy, not just electrons by themselves.

    I'm sorry but you've regressed about 100 years in science with this way of thinking. The classical approach cannot do what you want it to do. If you want to use a classical approach then you now need to explain, using classical mechanics, why an electron doesn't spiral down into the nucleus in a few nanoseconds, why electrons can only exist in certain "orbitals", and a number of other phenomena that scientists encountered a century ago. The attempt to answer these questions led straight to quantum physics, which explains and correctly predicts a huge range of phenomena with unparalleled accuracy at this scale. Abandoning quantum physics would be like abandoning General Relativity for newtonian mechanics just because you don't think "bending space" makes sense.

    So you want to abandon QM, but you actually don't...

    And QM does provide an explanation for the change in the mass of the system. It's called binding energy.

    There is no such thing as a "mass field".
  13. Jun 18, 2016 #12


    Staff: Mentor

    Thread closed for moderation

    Edit: the thread will remain closed. Electrons do not have different mass when they are in different orbitals, but atoms do have different mass when their electrons are in different orbitals. Almost all of the OPs misconceptions stem from not recognizing that distinction.
    Last edited: Jun 18, 2016
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Do Electrons have different mass when in different orbitals?
  1. THe differences (Replies: 1)