# Homework Help: Conflict with atomic model.

1. Oct 26, 2008

### ovais

1[ Now in the 2nd year of b.tech I, since was in class 9th not understanding how Bohr modified the earlier Rutherford atomic model.It is known to me that Rutherford atomic model was failed because it could not satisfy the electromegnetic principle,according to wich an elecltron continue to lose energy as it revolves around another charge(nucleus).Bhor modified the earlier model by stating each orbit with fixed orbit.I am not understanding when electromagnetic theory demands electron to continously lose energy,how then Bhor let the orbits of moving electron with fixed energy to explain the stability of atom.]

2. Relevant equations no equations needed

3. The attempt at a solution.I am not understanding when electromagnetic theory demands electron to continously lose energy,how then Bhor let the orbits of moving electron with fixed energy to explain the stability of atom.]

2. Oct 26, 2008

### merryjman

If the electron was assumed to orbit the nucleus, that meant that the electron was experiencing an acceleration (since its velocity would always be changing). Because the electron was viewed as a wave, it had to shoot off waves in order to change direction and conserve momentum, and this means losing energy. In fact, this happens at particle accelerator labs like Fermilab and CERN; the accelerating particles give off X-rays.

This would mean that the electron could emit all sorts of different EM waves (different colors) corresponding to the amount of energy lost. But it was observed that (for example) the Hydrogen atom only emitted certain colors when excited. Bohr explained this by assuming only certain circular orbits were allowed, so that when the electron gained or lost energy it would always be the same energies (colors) being gained or lost.

3. Oct 26, 2008

### borgwal

Correcting merryjman: In the classical model of an atom the electron certainly was *not* seen as a wave. But an accelerating charge in classical theory should continuously emit radiation. An atom certainly doesn't do that.

The Bohr model explained that not only is light emitted only at certain frequencies, but there is also a lowest energy state in which the electron is stable and no longer emits any radiation.