assess the restrictions of the Rutherford and also Bohr atom models

investigate the line emission spectra to examine the Balmer collection in hydrogen (ACSPH138)

Limitations that Rutherford’ Atomic Model

There room three main limitations:

Rutherford"s model failed to deal with how and also why the electrons were secure in their orbits. In other words, electrons did not decay to collide v the nucleus. 

In timeless physics, increasing particles emit power including ones experience circular motion. In this case, why do electrons not emit energy in spite of experiencing electrostatic attraction in the direction of the positive nucleus? 
The model could not offer a description of wherein the electron were.The constituents of the nucleus might not be explained clearly, that is, the constituents to be unknown. Rutherford and also the outsdrta.netes from the Geiger-Marsden experiment only demonstrated its confident nature.

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Bohr’s atomic Model 

Niels" Bohr"s atomic design overcame the limitations of Rutherford"s model.

Niels Bohr proposed 3 postulates in his atomic model:

Electrons exist and orbit in stable and also circular orbits around the nucleus under the affect of electrostatic attraction. In these orbits, electrons carry out not emit energy.


 Bohr’s version of the atom describes electrons orbiting in stable power levels as opposed to Rutherford"s version in i beg your pardon electrons" motion was no described.

Energy is took in or emitted is specific packets dubbed quanta once electrons relocate from one stable power level sdrta.nete another. The photon emitted has energy given by E = Ef - EiElectrons orbited the nucleus such that their angular inert is an integral multiple o. In other words, the angular inert of electron is quantised.


Bohr’s postulates to be based turn off the hydrogen spectrum.

Spectral lines it was observed in the Balmer collection or hydrogen spectrum (part of) are a an outsdrta.nete of electronic shift from higher energy level to n = 2. Knowledge the Lyman and Paschen series are not forced in detail but students are resdrta.netmended to be conscious of what castle represent.

The discrete power levels the electrons carry out an explanation because that hydrogen’s emissions spectrum when it is excited by a resource of energy. Bohr proposed that the emission bands stand for electrons’ transition in between these discrete orbits.The absorption of energy will enable an electron to with a greater energy levelWhen one electron return to its soil state (usual power level), the power that was absorbed is currently emitted in the form of clearly shows light.Bohr’s model of the atom allowed scientists to predict the power levels in a hydrogen atom native spectroscopy data.


The Balmer Series

The emissions spectrum the hydrogen created when an electron returns to the 2nd electron orbit (n = 9) is formally as the Balmer series as shown below.


The energy levels sdrta.nete to be closer, the further away they room from the nucleus. This reasons the emission lines to it is in closer in the direction of the higher energy (shorter wavelength) region of the spectrum.


Table shows the energy difference, wavelength and colour associated with every electron transition of the Balmer Series

Transition of n









Wavelength (nm)









Energy distinction (eV)
















Limitations that Bohr"s atomic Model

There are several restrictions of Bohr"s model.

Firstly, the design is a mix of both classical and quantum physics. The circular movement of electrons stems from classic physics while the quantisation that its inert is an applications of quantum physics.There is likewise a lack of proof supporting his postulates and model, thus having no theoretical justification. There was also no explanation as to why no energy is emitted indigenous the orbiting electronsRelative soot of the spectral lines might not be described when observing the spectrum. Part lines appeared brighter than others and Bohr"s model might not describe this.Larger atoms might not be described by the Bohr model. Predictions make by Bohr’s model is just accurate because that unielectron species (atoms or ion with just one electron in that is outermost orbit) e.g. He+. However, the accuracy of this predictions decreases together the efficient nuclear fee of one atom or ion increases (due to greater number of protons).Hyperfine Splitting, i beg your pardon is the figure of lines very close with each other on a close examination. Every line actually consisted of a variety of smaller lines, something i m sorry Bohr"s design did no predict (it predicted only one line for each transition).

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The Zeeman Effect, emerging when a solid magnetic field was passed with the discharge tube (containing hydrogen) raising the hyperfine splitting, also could not be described by the model.Electrons own magnetic minute which contributes to your stable energy levels. When a strong magnetic ar is present, this magnetic residential property of electron is inevitably affected which leader to changes to the power states. However, the transforms are fairly insignificant which offers rise sdrta.nete hyperfine lines.



Practice question 1

What space Bohr"s postulates in his atom model? (2 marks)

Practice concern 2

Explain why Bohr"s atomic design is a mixture in between classical and also quantum physics. (2 marks)