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[Phys-L] the Bohr atom, or not



Hi Folks --

Let me start a discussion by giving one side of the argument:

Suggestion #1: If you feel the urge to tell your introductory physics
class about the Bohr model, lie down until the feeling goes away.

Suggestion #2: If you feel obliged to mention the constant known as the
Bohr radius, you could derive it using a particle-in-a-box argument.
See e.g. Feynman volume III page 2-6.

Rationale: The effort involved for writing down the particle-in-a-box
wavefunctions is less than for writing down the circular Bohr orbits.
It is no less correct, and is incomparably better as a foundation for
further developments.

Suggestion #3: Instead (or additionally), you could model the atom as
a harmonic oscillator, i.e. as a charged mass on a spring. Then talk
about the states of a quantum harmonic oscillator. Again, this is
incomparably more useful as a foundation for further developments.

==========

It has been known for more than 80 years that the Bohr model is not
the right picture. Unless I'm missing something, there is no good
reason to mention it at all. Everything about it will have to be
unlearned as a prerequisite to understanding anything about quantum
mechanics in general or atoms in particular.

Anybody who wants to know the history of it can go sign up for a
course over in the history department, where they talk about caloric
and phlogiston and time-dilation and brontosauruses et cetera.

===============================

Would anybody care to make the counterargument? I don't recall ever
hearing an argument in favor of the Bohr model ... and it is easy to
find textbooks that don't mention it all (including at least one set
of large, red, 50-year-old textbooks) ... yet other books continue to
mention it, even in the most recent editions. What am I missing?