Why do we still teach Bohrs Model?

[whitay]

Why do some education systems still continue to teach Bohr's model even though it's seen to be incorrect?

 

[micromass]

Why do we still teach classical mechanics even though there is GR and QM which provide a more general theory?

 

[dauto]

Why teach classical mechanics when it's seen to be incorrect? Same thing can be said about the vast majority of physics. All physical models have limitations. As long as you understand what those limitations are, the models may have value.

 

[UltrafastPED]

Because it was historically important, is quite simple and elegant, and clearly illustrates how quantum physics differs from classical physics.

Of course it was not the last word ... and it underwent changes between 1913 and 1923.

 

[whitay]

So main points about teaching Bohr's model are,

- It is historically significant.

- The limitations of the model need to be identified and explored.

- It exemplifies the transition from classical physics to quantum physics.

Is there anything else I should look at?

The reason I am raising this for discussion is because I am trying to determine the justification and validity of idealizing Bohr's model in introductory physics syllabus'.

 

[jtbell]

I used to teach a second-year college/university "intro modern physics" course that included the Bohr model. I eventually stopped spending time on the details of the classical-mechanics type derivations associated with it (centripetal force, speed of the electron in an orbit, etc.) and assigning homework problems relating to those details. I did this because I had the feeling that spending too much time on the Bohr model "fixed" it in students' minds firmly enough that it interfered with learning the quantum-mechanical model of the hydrogen atom later.

I kept only the formula for the discrete energy levels, which one can get directly from the Rydberg formula for the hydrogen spectrum and Planck's formula for energy and frequency, and gave the usual exercises on spectral lines and energy-level transitions. Otherwise I discussed the Bohr model only briefly, qualitatively, as part of the historical background leading up to quantum mechanics.

I then introduced Schrödinger's equation and covered the usual simple solutions (particle in a box etc.), working up to the hydrogen atom, from which one can see where the discrete energy levels actually come from.

 

[adjacent]

I eventually stopped spending time on the details of the classical-mechanics type derivations associated with it (centripetal force, speed of the electron in an orbit, etc.) and assigning homework problems relating to those details.

I kept only the formula for the discrete energy levels and gave the usual exercises on spectral lines and energy-level transitions.

Then how did they do those in the exams?

 

[Nick O]

My chemistry professor emphasized its usefulness when dealing with ions that have only one electron, such as Li(2-).

 

[jtbell]

I eventually stopped spending time on the details of the classical-mechanics type derivations associated with it (centripetal force, speed of the electron in an orbit, etc.) and assigning homework problems relating to those details.

Then how did they do those in the exams?

I simply did not include that material in my exams. In the US, professors write their own exams for their courses.

 

[Meson080]

It becomes complex to understand updated theory without the outdated theory. So, you must read Bohr's model.

 

[whitay]

Ok. So we've outlined the importance of Bohr's model and I do agree that it is a great stepping stone into quantum physics. But would it be advisable to teach Bohr's model without introducing model of the Hydrogen atom etc?

I fear that students will take Bohr's model as gospel if only it is taught and other models are not elaborated upon.