According to Bohr model of atom, electrons move up an energy level in presence of EM field and emit a photon moving down the level.

In complete absence of any external EM field, shouldn't the electron collapse into the nucleus since it would keep losing energy as photons but wouldn't gain any?

(I do know (a little) about quantum mechanics and also that Bohr model is severely lacking. I was wondering if Bohr model had explained this phenomenon.)

  • 7
    $\begingroup$ Yes it should, so Bohr atom is impossible. End of story. $\endgroup$ Feb 2 at 11:31
  • 2
    $\begingroup$ I'd suggest learning some basic quantum mechanics since this observation was one of the key anomalies that led to its development. $\endgroup$
    – matt_black
    Feb 2 at 11:36
  • 1
    $\begingroup$ No, Bohr's model hadn't explained this phenomenon(historically). But during that time the idea of 'Quantum ' hadn't been yet applied to matter. By taking the ad hoc assumption that electrons can occupy only some specific orbits in which the angular momentum has specific values(quantised) and by assuming that in these energy levels it does not radiate energy(another ad hoc assumption), Bohr basically explained the major features of the atomic spectrum which was a great feat at that time since there was no classical explanation for the discrete nature of atomic spectra. $\endgroup$
    – user102687
    Feb 6 at 17:36

This collapsing electron orbit issue was a stumble stone for the last major classical Rutherford model of an atom. According to the classical electrodynamics, an electron accelerated by a central force should emit radiation and finally collapse on the nucleus.

The Bohr model of an atom was the first major quantum atomic model, addressing this electron collapsing issue. It has been postulated that just particular energy levels are allowed, where de Broglie matter wave of an electron forms a standing wave along its orbit.

The Bohr model was significant progress in its time, predicting many observations. But it was later abandoned for its various shortcomings. The major issue was addressing the electron orbital angular momentum and problems with its zero value ( the quantum number $\ell=0$ ).

It was replaced by the quantum model based on the Schroedinger's wave equation, that came with the concept of orbitals.

Later came the Pauli(Schroedinger-Pauli) equation addressing spin and then models involving Special relativity as Klein-Gordon equation or more famous Dirac equation.

The consequences of the Dirac equation are predictions of antimatter before it was observed ( specifically of a positron ) and natural integration of phenomena of quantum spin, that was until than rather an ad-hoc addition to non-relativistic models.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.