Electron motion in a p-orbital

1. Aug 26, 2010

ldv1452

In a p-orbital how does an electron travel from lobe to another if it must cross the nodal plane which has no electron density?

2. Aug 26, 2010

Redbelly98

Staff Emeritus
Welcome to PF!

It doesn't travel from one lobe to another, it is simultaneously in both lobes. More precisely, it has nonzero probability of being in each lobe, at every moment.

3. Aug 26, 2010

ldv1452

Thanks you. I'm still a little unclear on this. Is it that the electron does not actually travel through space? Or just that we can not determine its position so we rely on probability?

4. Aug 26, 2010

alxm

Well this is somewhat of an interpretation issue. But the usual view is that it's position is indefinite. The electron is 'moving', in the sense that it has kinetic energy (and some other properties of motion) however it is not moving in the classical sense where it has a definite position and momentum at every point in time.

5. Aug 26, 2010

ldv1452

This is very interesting. So are you saying that at a given point in time an electron may not have a position (in the sense that it physically is not anywhere) or that it has no "position" per say because we can not determine it? And if its the former then where is the electron at that point in time?

6. Aug 26, 2010

alxm

It's somewhere. You have the wave function (which, for a single electron, is what the orbital is), which tells us the probabilities that the electron will be in different locations. The total probability sums up to 1. This probability density is in fact directly observable, because it's the same thing as the charge density around the atom.

It's not that we can't determine it. (see the threads on the Heisenberg uncertainty principle) It's that it is genuinely 'undetermined'. (which is not to say we don't know anything about it. In fact, as far as we know, the wave function tells us everything that we can know about it) Of course, even if it did have a definite location (which we just didn't know about), which some interpretations of QM hold, then that position would still not have much real significance, because the uncertainty principle means that any attempt to measure the position to within the size of an atom, would change the momentum of the electron so much that it would be kicked out of the atom.

So, it doesn't have a definite location, and even if it did, you wouldn't really be able to do much with it in practice. (so the interpretational thing is more philosophical in this respect)

7. Aug 26, 2010

Staff: Mentor

There is simply no generally accepted answer to these questions. This is the subject of the various interpretations of QM. People who study these interpretations seriously, or do research in them, disagree vigorously among themselves on these issues. Look at the longest-running threads in this very forum. They're all about interpretational issues, and topics related to Bell's Theorem, which puts restrictions on what kind of interpretations are valid.

8. Aug 26, 2010

shredder666

and remember just because the shape of p looks like a dumbbell doesn't mean its confined in it, theres a minute probablility that it could be just a bit outside of the shape that we happened to define it to be.

9. Aug 26, 2010

ldv1452

Very enlightening responses everyone. Thank you.

10. Aug 27, 2010

Redbelly98

Staff Emeritus
I like that.