Bohrs atommodel

Bohrs atommodel bygger på Rutherfords atommodel, hvor negativt ladede elektroner bevæger sig i rundt om en positivt ladet kerne. Det geniale ved Bohrs atommodel er derfor ikke selve modellen, men skridtet med postulatet om at elektronerne er i stationære baner (dvs. de falder ikke ind i kernen efter et stykke tid pga. Coulomb-kræfterne mellem den positive ladning og den negative ladning).

"It is obvious that the behaviour of such a system will be very different from that of an atomic system occurring in nature. In the first place, the actual atoms in their permanent state seem to have absolutely fixed dimensions and frequencies. Further, if we consider any molecular process, the result seems always to be that after a certain amount of energy characteristic for the systems in question is radiated out, the systems will again settle down in a stable state of equilibrium, in which the distances apart of the particles are of the same order of magniture as before the process.

Now the essentail point in Planck's theory of radiation is that the energy radiation from an atomic system does not take place in the continuous way assumed in the ordinary electrodynamics, but tha is, on the contrary, takes place in distinctly separated emissions, the amount of energy radiated out from an atomic vibrator of frequency ν in a single emission being equal to τhν, where τ is an entire number, and h is a universal constant."

[N. Bohr, "On the Constitution of Atoms and Molecules", Philosophical Jounal, juli, 2013]

Netop sammenhængen mellem atomets elektroners baner og lysets diskrete spektrum udsendt fra atomet førte Bohr på sporet af den rigtige forståelse: At elektronerne kun kan befinde sig i helt bestemte energitilstande i forhold til atomkernen. Hvis ikke ville strålingen for det første være kontinuerlig og for det andet ville elektronerne gå til grunde efter kort tid, da de ville spirallere ind i atomkernen.

Med Borhs atommodel kan hydrogenspektret forklares.

Jon, december 2010