# Modern physics

roshan2004
Why the rutherford atomic model can't explain the line spectra of the hydrogen atom?

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the most essential is that a spiralling charge will emit radiation and thus loose energy making the atom collapse.

roshan2004
But,that only explains the unstability of atom.The question is about the spectra.

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if the atom is unstable, will there be a spectra? Well, it will be continuous -> compare with bremsstrahlung spectra.

roshan2004
So,Can I say this-Because the atom is spiralling down towards the nucleus,it will continuoulsly be giving the radiation forming a single wavelength,continuous spectra.

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I would not say that it will forming a single wavelenght, that is a discrete spectrum. Your sentence is a self contradiction.

roshan2004
So,how do I explain the reason then..........

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you just drop the "forming a single wavelength" part.

roshan2004
How about this-Rutherford's model suggests that the electrons can float around at any energy level they want, and that photons of any frequency or wavelength can be emitted.

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no electrons can not float around as they want! The rutherford model is a classical, non-quantum, model where electrons are orbiting the nuclei as planets orbiting the sun.

But the electrons are then under a radial acceleration, centripetal acceleration, and accelerating charges will emit radiation of continuous spectrum - there will be no stable energy levels and no atom will be stable.

roshan2004
So it means that they are continuously giving radiation of same type in rutherford which give a continuous radiation.

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the radiation is continuous in time and in wavelength

roshan2004
Thanks mate,are there any links that you know which has got the lectures on bohr's model of atom along with rutherford's and sommerfield's.

roshan2004
Why the orbit energy in bohr model is negative?

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all bound states has negative energy. (It all boils down to where you define the 0 level of energy).

roshan2004
What is meant by bound states?

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have you not done classical mechanics with planetary orbits and stuff? :O

roughly speaking, a system is bound if it's kinetic energy in the centre of mass system is smaller than the potential energy.

roshan2004
Thanks

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and since one often counts potential energy as negative, the energy of a bound system will become negative.

roshan2004
Really appreciate all your labour mate.

Bob_for_short
Why the Rutherford atomic model can't explain the line spectra of the hydrogen atom?

In a certain approximation, it can. If your electron starts falling from infinity (or just from very distant place), it radiates a quasi-continuous spectrum. This is called a radiative recombination. But it stops falling into the potential well before reaching the nucleus: its "lowest" orbit is determined with quantum mechanics. In fact, the electron can be captured by the nucleus in some cases (http://en.wikipedia.org/wiki/K-capture). In this sense, it can "reach" the nucleus and form a neutral particle with a proton.

Bob.