[khwcm]

Combining 2 ideas that i have, for hydrogen atom:
1) electron is quantized in an atom
2) electron density(probability of finding electron) against distance from nucleus(R) graph

so, we may see that, at different R, we may still find an electron due to the wave properties

WLOG, assume an electron move away from nucleus in the same energy level(ground state), so PE remain unchange. since no external energy is given to the atom, total energy remain unchange.

my question is:
What changes can lead to the electron move furthur?

[Jorriss]

Are you talking before or after a measurement? Your question is, to me, unclear.


It seems the issue is that (even though you seem to see this is not the right perspective) you are talking about the electron as if it is a planet in orbit or a particle following classical physics.

As far as my understanding of quantum goes, nothing is making it move away from the nucleus in the traditional sense as much as it doesn't have a definite distance from the nucleus until some measurement is made, so a question like, what makes it move away from the nucleus, isn't really a quantum question as you've posed it.  

Sorry if I misunderstood your question or point.

[McCoy]

Combining 2 ideas that i have, for hydrogen atom:
1) electron is quantized in an atom

What does that mean?

[khwcm]

Jorss:
you are right that i am thinking of "It seems the issue is that (even though you seem to see this is not the right perspective) you are talking about the electron as if it is a planet in orbit or a particle following classical physics."

however, in my mind, even electron does not move as an orbital, it only carries a fixed amount of total energy which is equivalent to sum of KE and PE. However, when electron move randomly(so that means different radius) in the same energy level, PE remain unchange. so what can make the electron not moving as an orbital( with fixed radius)?

McCoy :
for "electron is quantized in an atom", i mean electron move with fixed energy(should be PE, right?) in an atom

[McCoy]

McCoy :
for "electron is quantized in an atom", i mean electron move with fixed energy(should be PE, right?) in an atom

Okay personally, I always talk about quantization of what electron does (like its motion) which are results of quantization of energy. So that's why I was confused. By the way, no one knows for sure how electron moves in the nucleus.  But I don't think it moves randomly...it follows some path religiously but i don't know how!

[Jorriss]

McCoy :
for "electron is quantized in an atom", i mean electron move with fixed energy(should be PE, right?) in an atom

Okay personally, I always talk about quantization of what electron does (like its motion) which are results of quantization of energy. So that's why I was confused. By the way, no one knows for sure how electron moves in the nucleus.  But I don't think it moves randomly...it follows some path religiously but i don't know how!

It doesn't follow a path - until something disturbs the system, it doesn't 'exist' anywhere finitely at all. You can only discuss it's path in terms of probabilities of finding it in a particular area.

[McCoy]

It doesn't follow a path - until something disturbs the system, it doesn't 'exist' anywhere finitely at all. You can only discuss it's path in terms of probabilities of finding it in a particular area.

I think the idea of path is even wrong altogether because it doesn't make sense. I used it for luck of words. By the way, knowing the probability density doesn't translate into know how the electron is moving. As I said, no one knows how it moves.

[Jorriss]

It doesn't follow a path - until something disturbs the system, it doesn't 'exist' anywhere finitely at all. You can only discuss it's path in terms of probabilities of finding it in a particular area.

By the way, knowing the probability density doesn't translate into know how the electron is moving. As I said, no one knows how it moves.

Yeah, that's why I went along with what you said and phrased it the way I did.

[McCoy]

"Yeah, that's why I went along with what you said and phrased it the way I did."

I see. cheers. I think quantum mechanics is an incomplete theory!

[khwcm]

ok....so let me change my tone...and consider this "new" problem i have:

from the electron density(probability of finding electron) against distance from nucleus(R) graph, it is probable(when probability not equal to 0) for us to find an electron at 2 distinct radius, say, r1, r2.

since electron is in ground state, they are in the same energy level. which means they have same PE.

again: Total energy = PE + KE. why can an electron move in different position with different radius but with same PE?



 

[Yggdrasil]

For an electron in a wavefunction associated with a particular energy, you can't really think of the electron as moving away from the atom and having the same potential energy.  Because of quantum mechanics and the uncertainty principle, if we know the energy of an electron we cannot know the position (the hamiltonian and the position operator do not commute).  The electron is basically spread out between all of the points in its radial distribution function and is not really moving between positions within that distribution.

[McCoy]

ok....so let me change my tone...and consider this "new" problem i have:

from the electron density(probability of finding electron) against distance from nucleus(R) graph, it is probable(when probability not equal to 0) for us to find an electron at 2 distinct radius, say, r1, r2.

since electron is in ground state, they are in the same energy level. which means they have same PE.

again: Total energy = PE + KE. why can an electron move in different position with different radius but with same PE?

Yggdrasil is right. As an analogy, you can't increase the radius of the same circle and expect same area! 

[khwcm]

actually....i am quite messy >.< ....may you please elaborate more about that?

does it mean that the electron is move with FIXED radius and in wave form, which is similar to the Bohr model?

isnt electron can exist in different position(with different position) so we call that as electron "cloud"?

[McCoy]

actually....i am quite messy >.< ....may you please elaborate more about that?

does it mean that the electron is move with FIXED radius and in wave form, which is similar to the Bohr model?

isnt electron can exist in different position(with different position) so we call that as electron "cloud"?

...considering electron to be moving in fixed radius is a bohr model, which is wrong but it's still beig used beacuse it's easy to understand. Electrons don't move around the nucleus. No one knows what electron does around the nucleus....u can't say electron has this velocity, position or momentum ....they exists in mixed states.
electron cloud is electron density which is a result psi squared. this thing is not good mate...i'd suggest you chat with your professor about it.