Re: Bohr's Atom still number one

The_Man <me_so_horneeeee@xxxxxxxxx> wrote in
news:1178572539.034098.14560@xxxxxxxxxxxxxxxxxxxxxxxxxxxx:

On May 5, 4:29 pm, bz <bz+...@xxxxxxxxxxxxxxxxxxxx> wrote:
"g...@xxxxxxxxxxx" <g...@xxxxxxxxxxx> wrote
innews:1178394138.430885.325220@xxxxxxxxxxxxxxxxxxxxxxxxxxx:



On May 5, 10:41 am, bz <bz+...@xxxxxxxxxxxxxxxxxxxx> wrote:
snip too long

....
My main point is that the Bohr model predicts a
rapid loss of energy with all electrons collapsing into the nucleus.
Bohr could not explain why orbiting electrons would not radiate
constantly.

Bohr could not (well) explain why electrons would not radiate.

Agreed.

His
best explanation was that the electrons were confined to "orbits" of
specific energy.

Not a very good explanation as 'orbits' implied circular motion, centripedal
acceleration and radiation.

You suggest that electrons would collapse into the nucleus in the Bohr
model. This is not accurate.
.....
The collapse into the nucleus is the classical prediction. Since Bohr
knew already that this didn't happen, he had to model WHY this doesn't
happen. He had mostly ad hoc explanations.

You are correct, it is the classical prediction. Bohr did know it didn't
happen. He didn't know why.

.....

He ran into another problem. His model only works for a hydrogen atom with a
single electron.

.....
What makes you think they have a high velocity in the atom?

One can easily calculate the KE of an electron, and therefore its
velocity.

That assumes that the energy is expressed as a linear motion (along with a
centripedal force, producing a circular motion). One can certainly calculate
an orbital velocity for the electrons. However it fails to explain why
electrons undergoing such motion would not be radiating constantly.

Core electrons travel at approximately c/ Z, where Z is the
nuclear charge. When Z gets large, the speed of the electrons becomes
sufficiently close to c, so that relativistic effects become very
important.

Are such effects observed? Wouldn't the atomic mass be effected?

If electrons were fired at an atom with the same velocity as the calculated
velocity for a Bohr orbit, what would happen?

They don't in the modern atomic theory, but, you are correct when you
think that, in Bohrs model, they will need to be traveling.

They will need to be attracted to the nucleus. That attraction will
'push' them toward the nucleus. Only their speed keeps them from
reaching it.

In fact, s electrons have a non-zero probability of being In the
nucleus. Such is the basis of the hyperfine interaction.

Agreed. A significant probability. But this steps outside Bohr's model.

Electrons, when ever they travel at a high speed and their direction of
travel is changed, radiate energy.

This is not true.

When is it not true?

The KE of a particle can be visualized by examining
the wavefunction. Where the wavefunction is highly curved, the KE is
high. Where the wavefunction is slowly changing, the KE is low. Since
the wavefunction for a 1s orbital is essentially exp(-r), the function
is obviously more highly curved near the nucleus, than at infinity.

Agreed, but what does this have to do with showing flaws in the Bohr model?

I am trying to show guskz the problems with Bohr's model and where it fails
to correspond with observations.

We DO observe that electrons, when their path is changed, radiate energy.


--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

bz+nanae@xxxxxxxxxxxxxxxxxxxx


--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

bz+spr@xxxxxxxxxxxxxxxxxxxx remove ch100-5 to avoid spam trap
.

Relevant Pages

  • Re: Bohrs Atom still number one
    ... rapid loss of energy with all electrons collapsing into the nucleus. ... Bohr could not explain why orbiting electrons would not radiate ... Because they are undergoing constant acceleration toward the nucleus, ...
    (sci.physics.relativity)
  • Re: Disproving evolution
    ... all, from Maxwell to the discovery that electrons existed, dates ... But there were theories of the atom that did not have radiating ... The objection that such electrons would radiate was made right ... The Bohr model was in 1913. ...
    (talk.origins)
  • Re: Bohrs Atom still number one
    ... rapid loss of energy with all electrons collapsing into the nucleus. ... Bohr could not explain why orbiting electrons would not radiate ...
    (sci.physics.relativity)
  • Re: Bohrs Atom still number one
    ... rapid loss of energy with all electrons collapsing into the nucleus. ... Bohr could not explain why orbiting electrons would not radiate ...
    (sci.physics.relativity)
  • Re: what is the relation between force and energy?
    ... But irretrievably grounded on the Bohr model. ... circle and requires angular momentum. ... Bohr for electrons to have differing angular momenta even if they have ...
    (sci.physics)