[Gargamel]

Hello

In my book it says that an electron only can have a well-defined energy like the circels in Bohr's model.
In the book it also says that Bohrs model is not the true reality because the electrons is kinda located in an electron cloud.

I might be wrong on this: When i look at the electron cloud the electron must possess the same energy according to Bohr. If this is true I imagine that when an electron is closer to the nucleus it must have a higher speed compared to when it is far from the nucleus (kinetic energy+potential energy = constant for that particular electron)

Can someone please confirm my way of thinking. Im a bit curious if I can use the classical laws from physics to explain this, so I might be wrong because my book doesnt say anything about the electrons speed...and it says that classic physics can be used.

Thx for reading

[MrTeo]

I might be wrong on this: When i look at the electron cloud the electron must possess the same energy according to Bohr. If this is true I imagine that when an electron is closer to the nucleus it must have a higher speed compared to when it is far from the nucleus (kinetic energy+potential energy = constant for that particular electron)

Not really, as Bohr's values for radii only mark the average or "more probable (in terms of radial probability)" position of the electron while the cloud extends in space. Moreover we can't really find out the electron's speed because of a certain grade of indetermination of the measure caused by Heisenberg's principle. You're right when you say that lower electrons have got an higher speed but quite often speeds between one level and the other are quite close, and that's why electrons "jump" form one level to the other and also many bonds form. Bohr's model accords quite well with previsions (just think at the fact that Rydberg's formula comes from that model) if you don't consider much of the problems related to atomic physics: this is why you can also derive it from classical mechanics, just considering the equilibrium of a mass (the electron) rotating around the nucleus and thinking at the angular moment of an electron as a multiple of $$ \frac{h}{2\pi} /$$ (due to quantization of energy).

[Gargamel]

Okay, thx for the answer, this really help my understanding. (im not quite sure i understand all of it, but i understand that electrons in the same shell must have a higher velocity when they are closer to the nucleus, compared to electrons in the same shell but a more far away from the nucleus)

(in my first thread it should be "and it says that classical physics can not be used". But cant modify it)

[MrTeo]

Well, as your book says, if we're working in a quantum-mechanical perspective we can't use classical physics... but this is a really hard way to analyze the atomic structure (even if it's the best model). Working with classical physics we can see a few interesting things about electrons and orbitals tough they only partially accord to experimental results.