The Hydrogen Atom: An Unique Case of Quantum Numbers

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Discussion Overview

The discussion centers on the unique characteristics of the hydrogen atom in relation to quantum numbers, particularly why its energy levels depend solely on the principal quantum number n, unlike other atoms where energies depend on both the principal quantum number and the orbital quantum number. The scope includes theoretical aspects of quantum mechanics and the implications of various interactions and effects on energy levels.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions why hydrogen is unique in its dependence on the principal quantum number n, suggesting that other elements have energies influenced by both n and the orbital quantum number.
  • Another participant notes that electron-electron interactions in other atoms contribute to this difference.
  • A participant introduces the concept of the Runge-Lenz vector as an additional conserved quantity that explains the unique properties of hydrogen, linking it to the nature of orbits under different potential laws.
  • It is mentioned that fine structure effects introduce an l dependence in energy levels, particularly when considering relativistic effects as described by the Dirac equation.
  • Another participant asserts that l dependence will also be present in hydrogen atoms, indicating that real hydrogen atoms exhibit more complexity than the ideal model suggests.
  • Discussion includes the effects of spin-orbit coupling and interactions with the proton magnetic moment, which lead to fine and hyperfine structures in the energy levels of hydrogen.
  • One participant points out that perturbations such as external electric or magnetic fields can also introduce l and m dependence in hydrogen, referencing the Zeeman and Stark effects.
  • It is concluded that only the ideal hydrogen atom shows n dependence exclusively, while real hydrogen atoms exhibit l and m dependence due to various factors.

Areas of Agreement / Disagreement

Participants express differing views on the factors contributing to the energy level structure of hydrogen compared to other atoms. There is no consensus on the extent to which various effects influence the energy levels, indicating ongoing debate and exploration of the topic.

Contextual Notes

Limitations include the assumption of an ideal hydrogen atom versus real hydrogen atoms, as well as the dependence on external factors that may alter energy levels. The discussion does not resolve the complexities introduced by different interactions and effects.

albertsmith
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Why is the hydrogen the only atom that depends only on principal quantum number n and for all other elements, energies depend on both orbital quantum number and principal quantum number?
 
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in other atoms there will be electron-electron interactions.
 
Incomplete. The reason is an "extra" conserved quantity, called the Runge-Lenz vector (check wikipedia). It's somehow, the same reason for which orbits close (i.e.: ellipses) under the 1/r^2 potential but they do not in general 1/r^p ones.

Also, if you take into account fine structure effects, there appears an "l" dependence of the energy levels. E.g., if you consider relativistic effects, as in Dirac eq.
 
And that L-dependence will also be around in hydrogen atoms.
 
The hydrogen atom has both spin-orbit coupling (coupling of the electron magnetic moment and the orbital magnetic moment) and coupling to the proton magnetic moment that create both fine structure and hyperfine structure of the electron energy levels. The famous ones are the Lamb shift and the 1420 MHz (21 cm electron-proton spin coupling) line in intergalactic hydrogen.
 
l dependence of hydrogen will also arise due to perturbations in the potential, such as an external electric or magnetic field. You can look up the Zeeman effect and the Stark effect.

SO! Really, only ideal hydrogen atom has only n dependence. Real hydrogen atoms have l and m dependence.
 

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