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View Full Version : Isnt it inaccurate to say Atoms are mostly empty space?



Sam99
2013-Feb-28, 09:31 AM
Doesn't this imply they are classical objects that have definite positions all the time?

Wouldn't it be meaningless to say its empty under the copenhagen interpretation? Instead an electron shell is empty only when measured at a particular instant?

Please clarify. thank you

grapes
2013-Feb-28, 10:18 AM
Wouldn't it be meaningless to say its empty under the copenhagen interpretation? Instead an electron shell is empty only when measured at a particular instant?

What would be your way of saying it if it is not measured at a particular instant?

antoniseb
2013-Feb-28, 12:12 PM
Doesn't this imply they are classical objects that have definite positions all the time?...

I'm not sure how often you read anything between scientists in which something depends on whether or not electron clouds (or protons and neutrons for that matter) are mostly empty space. By the time you get down to atom-sized or nucleon-sized smallness, words like empty and space start needing new meanings outside the sense the language developed over the centuries. When you read that atoms are mostly empty space, you are reading something for the popular press to explain a limited idea to lay-people.

Jens
2013-Mar-01, 06:23 AM
I think in fact that the probability shell extends to infinity, though the likelihood becomes very, very, very small, so in that sense there would be no empty space in the universe at all. But as others have said, this is only the statistical probability. If you measure it you will find it only in one place, and indeed you will find lots and lots of empty space where you didn't find it.

Sam99
2013-Mar-02, 01:51 PM
What would be your way of saying it if it is not measured at a particular instant?

Hmm its full?
If I understand your Q. its meaningless under the Copenhagen picture. It forces us to consider the wave-particle duality. Which is where our vocabulary runs out & can only make progress with the math & theory. This is what they mean by no one understands the quantum world at least not in a pictorial way.

lpetrich
2013-Mar-08, 06:04 AM
I think that it is inaccurate, because the atoms' electrons' wavefunctions stretch over the extent of atoms. In fact, that's what gives atoms their sizes.

In fact, in the Standard Model, electrons are described by the Dirac equation, which is a wave equation, like Maxwell's equations for the photon. I recall a physics professor who called photons "blobs of light", and electrons are much the same.

Cougar
2013-Mar-09, 01:40 PM
...electrons' wavefunctions stretch over the extent of atoms.

Can't argue with that. But at the same time, if you fire electrons at a hydrogen atom, you may see some deflection due to charge, but the electrons will very rarely hit anything. I still think the analogy is accurate: If an atom was the size of a cathedral, the atom's nucleus would be no bigger than a fly.

Ara Pacis
2013-Mar-09, 09:00 PM
Are electrons constrained to the orbital shells, which have a specific shape and thickness and altitude distance. I always figured the shells were like thin membranes such that the space in between the membranes was empty, but maybe that's incorrect.

lpetrich
2013-Mar-09, 09:19 PM
They are not thin shells, but thick and overlapping. Schematic diagrams can be misleading.

Ara Pacis
2013-Mar-10, 01:16 AM
They are not thin shells, but thick and overlapping. Schematic diagrams can be misleading.

Ah, then the idea that an electron moves from one shell to another shell almost instantaneously is inaccurate? That was a big leap and a big question back when I was in HS.

lpetrich
2013-Mar-10, 01:43 AM
The electron sort of spirals inward or outward as it goes from one state to the other.

I might have to try to work it out in detail for a "toy" system, like a 2-state system.

grapes
2013-Mar-10, 11:31 AM
Hmm its full?

Analogies are never perfect, but imagine sticking your hand into the vicinity of a rotating airplane propellor. Yes, the propellor "fills up" a considerable amount of space, but how much "really"?