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"the most remarkable success of the Bohr's theory is that it provides a satisfactory explanation for the line spectrum of hydrogen."

But what is the problem with line spectrum of hydrogen which could not explained before the Bohr's theory was introduced and how it was explained by Bohr's theory?

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  • $\begingroup$ what do you mean by quantization of energy. $\endgroup$ May 27 '15 at 16:18
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    $\begingroup$ @PushkarSoni, do you have an idea what is Bohr model actually is? If not, first read about it, then if something is unclear, please, ask. $\endgroup$
    – Wildcat
    May 27 '15 at 16:25
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    $\begingroup$ @LordStryker, Bohr model by no means explained why electrons do not fall into the nucleus. It just takes this fact for granted. In fact, it uses this assertion as a starting point. Bohr's logic ultimately was: since electrons do not fall, there are some tricky orbits on which they move without radiating energy. Trying to reverse Bohr's argument would obviously be a perfect example of circular reasoning. :D $\endgroup$
    – Wildcat
    May 27 '15 at 16:35
  • $\begingroup$ @Wildcat Most certainly. However, it is used to illustrate these phenomena in a simple way. That is what I was trying to convey... $\endgroup$ May 27 '15 at 17:21
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Since this is pretty well covered in countless number of books and other sources I will try to just emphasise the key points.

  1. The emission spectrum of atomic hydrogen was well known at that time, the only problem was that no one was able to explain it. :D Where does all this lines come from, i.e. what physical process gives rise to such discrete spectrum?

  2. The wavelengths of spectral lines were known to be very well predicted by the Rydberg formula, but again no one was able to explain why this formula works, i.e. what are its physical justifications.

  3. Bohr model explained discrete spectrum as follows: spectral lines are due to electron transitions between stationary orbits. Bohr was also able to determine the actual energy spacing between levels in hydrogen atom and explain the reason for the structure of the Rydberg formula.

  4. However, Bohr failed to predict the lines in the emission spectrum even for helium atom. It happened simply because Bohr model is physically wrong. Electrons do not orbit around the nucleus.

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  • $\begingroup$ thanks now i understood. i have another question that why was the Bohr's model unable to explain the line spectra of multielectron atom, actually i don't even know what this actually means? please explain $\endgroup$ May 27 '15 at 16:30
  • $\begingroup$ @PushkarSoni, simply put, Bohr theory was wrong physical theory. Thus, it failed test on multielectron atoms and was eventually replaced by quantum theory. $\endgroup$
    – Wildcat
    May 27 '15 at 16:42
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    $\begingroup$ @PushkarSoni, oh, well, that would not be easy to explain. In few words: at microscopic level Mother Nature behaves very differently from our everyday experience. The very notion of trajectory does not longer make sense. $\endgroup$
    – Wildcat
    May 27 '15 at 16:53
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    $\begingroup$ @PushkarSoni, yes. Quantum mechanical description which operates just with the probabilities of finding an electron here and there is the working physical theory for an atom. $\endgroup$
    – Wildcat
    May 27 '15 at 16:55
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    $\begingroup$ @PushkarSoni, in case of any doubts better just post your question here (or at Physics.SE). The community will help much better (and faster) than any of its members individually. $\endgroup$
    – Wildcat
    May 27 '15 at 18:00

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