# Basic atomic picture clarification

1. Jan 31, 2009

### johndb

I find the mechanics of the atom are not clear to me. I understand that the Bohr "step" of electrons in orbit is non-applicable anymore, then there is De Broglie's wave theory, this is never built upon. I always find it just mentioned never expanded on, I'm left with basic questions, okay so do we now assume electrons orbit or move around the nucleus in wave-like motions, or perhaps they are stationary and bob/shift back and forth in a mechanic pendulum like manner and we note that it is this action which creates wave-like oscillations (surely not a suggestion which is too absurd). The other question is do they produce different shapes of wave with different amplititudes and frequencies. Does one have to involve the uncertainty principle and elecric forces to resolve this picture?

2. Jan 31, 2009

### ZapperZ

Staff Emeritus
The reason why this is seldom mentioned in the complete sense is because it cover whole chapters in an undergraduate QM class.

You can look at the painful details of the derivation for a hydrogen atom here. It isn't trivial, but every single physics major will have to know this cold.

Zz.

3. Jan 31, 2009

### johndb

I still think that for amateurs on the outside of such in depth physics, could be presented with a clearer picture as a framework/a big picture view in studying atomic physics a stepping stone to help them from getting lost, confused and frustrated. The questions that arose when the wave theory was introduced are still not answered. Can anyone reach this simplified level, do electrons orbit, do they stop, do they move in waves, is this asking too much?

4. Jan 31, 2009

### ZapperZ

Staff Emeritus
It is, because the words you use such as "move" and "orbit" no longer have clear meanings when we deal with QM. That's why in QM, the mathematical description comes first, and the English language that we use to describe it comes second. The word "waves" that are often used in QM isn't even a real wave. More often than not, it is simply a designation of the mathematical nature of the differential equation (i.e. the Schrodinger equation looks like a wave differential equation) and therefore, the solution is called a "wave function". But without the mathematical knowledge of it, one would be misled into thinking that this is your ordinary wave that one sees in classical optics. It isn't!

Often in QM, the question itself is the difficulty because we are trying to force a square object through a round hole, i.e. we are trying to force nature to give answers in ways that we have previously understood - our classical concepts.

There are, I think, many pop-science books (Gribbin has several) that has tried to explain QM, and may even have attempted to describe an atom. However, in all cases, they try to explain it via analogy or via one narrow specific example or special case. This is because as you can see, the full description of it isn't trivial. There are simply things that are just too complex to be reduced accurately into simpler forms. That may be the reason why you see a lot of holes in any layman description of an atom.

Zz.

5. Jan 31, 2009

### WaveJumper

And it's even harder to imagine the atom as a wave, as seen in the double slit experiment:

http://www.whatsnextnetwork.com/technology/index.php/2007/05/28/p5211

Maybe we are deficient in the imagination department.

6. Jan 31, 2009

### ZapperZ

Staff Emeritus
I'm not sure if it is more difficult, because it's the same principle as with any other "particles", including photons. So if we can describe the interferences pattern with photons, why not atoms.

The difficulty here is more on the experimental realization, because the atom has to be ultracold to make sure the whole atom is in a "coherent" state with its various constituents. We've seen atoms as big as buckyballs undergoing such phenomenon.

Zz.

7. Jan 31, 2009

### Redbelly98

Staff Emeritus
I'm not sure why you say this, or who "we" refers to. Surely such things were imagined at some point in the early 1900's, when ordinary matter was first described as having wave behavior.