difficulties with the Rutherford-Bohr model (1 Viewer)

[hys]

Identify [Recognise and name] the difficulties with the Rutherford-Bohr model, including its inability to completely explain:
-The spectra of larger atoms
-The existence of hyperfine spectral lines
-The Zeeman effect

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The Rutherford-Bohr model takes the first step to introduce quantum theory to the hydrogen atom but the model has many limitations and difficulties. For all of its success, the Bohr model of the atom had serious limitations, these include:

- It was an ad hoc mixture of classical and quantum physics. It assumed that some laws of classical physics held and others did not.
-It did not work for multi-electron atoms (hydrogen has only one electron).
- Certain spectral lines were found to consist of a number of very fine and close lines. The cause of these hyperfine spectral lines could not be explained.
- It could not explain the relative intensities of the spectral lines. Some lines were more intense than others. Why this should occur was unknown.
- The splitting of spectral lines when the sample was placed in a magnetic field the Zeeman effect could also not be explained.

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anyone got explanations why

 

[-=«MÄLÅÇhïtÊ»=-]

yup, i confirm dat, all u need to do is outline the 4 problems and explain why they were problems. You don't need to explain how they really work.

 

[hys]

Thanks for all contributions... yeah did some copy and pasting from excel but going to combine and rewrite with jacaranda notes

 

[spice girl]

-It was an ad hoc mixture of classical and quantum physics. It assumed that some laws of classical physics held and others did not.

Bohr said that electrons moved in discrete orbits. By assuming that they were discrete, he relied on quantum physics, but the idea of a determined, circular orbit relied on primitive classic concepts. It violates Heisenberg's Uncertainty Principle (which was invented later, pff...) which states essentially: "how do u know it's circular?"

-It did not work for multi-electron atoms (hydrogen has only one electron).

Electrons repel each other. This repulsion changes the energy levels, so the Rydberg equation only works for the one-electron atom.

- Certain spectral lines were found to consist of a number of very fine and close lines. The cause of these hyperfine spectral lines could not be explained.

It was explained in terms of "spin", later by Pauli, etc.

- It could not explain the relative intensities of the spectral lines. Some lines were more intense than others. Why this should occur was unknown.

Intensities of a certain wavelength is determined by the probability of the transition that caused the certain wavelength to be emitted. Calculations of this could not be developed by the Bohr model.

- The splitting of spectral lines when the sample was placed in a magnetic field ?the Zeeman effect ?could also not be explained.

Zeeman Effect is essentially the splitting of previously-discrete energy levels due to an external magnetic field (discrete = equal). This is later explained by the concept of electrons possessing magnetic spin (which you will learn in uni, if you're unfortunate), where the spin state which generates a magnetic dipole that opposes the external field is warped to a higher energy state, because electrons in these states are more uncomfortable...

 

[Big Willy]

i dont know much, but regarding the above post, isnt there 7 reasons?

I can only recall my teacher going "You got 6 marks for naming all 7 problems"

 

[-=«MÄLÅÇhïtÊ»=-]

will the syllabus says "the" 4 main difficulties. So i wouldn't state the wrong ones out of the 7 ur teacher told ya in the hsc.

 

[ronnknee]

This is helpful

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