Re: [Phys-L] the Bohr atom, or not

["John Clement" <clement@hal-pc.org>]

But the point of the abstract was ignored:
"We find that if the curriculum does not include sufficient connections
between different models, many students still have a Bohr-like view of atoms
rather than a more accurate Schrödinger model."

I suspect that the Bohr model automatically comes from studying classical
mechanics.  In other words students spontaneously use a Bohr like model
because the atom has analogous features to the Solar system.  The Bohr like
atom is around us in drawings, pictures, and is a very natural model.  So
bringing out the connections between the models, and bringing out how the
ideas developed can help students to move from one model to another.

Also notice that the authors pointed out that there is weak evidence that
avoiding the Bohr model helps student understanding.  So it can possible be
a good model to include in the student considerations.

Models for building student understanding can be radically changed, and
students need to understand this.  One goes from classical mechanics to
relatavistic mechanics by bending the model.  Students first have to
understand that the wave velocity is basically independent of the frequency
and does not change with frequency.  Once this simple idea is established,
then it can be bent and the second order effects which produce the rainbow
can be introduced.  But they should be aware that there is a "conflict" and
that the velocity independence rule is not hard and fixed.  At that point
they have to begin to understand 2 variable reasoning.  So the Bohr atom is
based on classical ideas and a brand new model had to be introduced.
Students who understand this will be better able to transfer to the new
model for the atom.

But I will admit that further research can be done on how to best effect the
transfer.

As to the Bohr atom going away, that is very unlikely.  To have it disappear
from students minds you would have to re-educate all teachers from K to
college and remove it from numerous books, videos, and pictures.  It is here
to stay, and student absorb it either naturally or by encountering it.  Just
putting the electron cloud idea into lower level texbooks just adds more
stuff that students memorize as opaque gobbledy goop.

I did read that whole paper a while ago.  Who else read more than just the
abstract?

John M. Clement
Houston, TX



> Thanks for that.
>
> Those authors say in part:
>   "we find that comparing and contrasting different models is 
> a key feature of 
>    a curriculum that helps students move beyond the Bohr 
> model and adopt 
>    Schrödinger’s view of the atom."
>
> Surely we all agree that comparing and contrasting different 
> models is a good thing ... but that doesn't mean that the 
> Bohr model needs to be part of the mix.  One can compare and contrast
>  -- models using waves on a string
>  -- models using waves in a pool of water
>  -- computer animations using dot-density plots
>  -- computer animations using amplitude and color-coded phase
>  -- lots of other things, each of which involves more sense and less
>   nonsense than the Bohr model.
>
> Bottom line:  What really bugs me is the messed-up sense of 
> priorities, i.e. 
> spending time on the Bohr model to the exclusion of so much 
> other stuff that would be in every way better.