We can't "see" an atom?

[neoweb]

I understand we can conduct experiments from which we can "infer" or "sense" that an atom or a certain number of atoms are present but we still can't physically "see" one, even with the most powerful microscope... true?

Nevertheless, are we still able to manipulate atoms, in the sense that we can put three and only three atoms of a particular kind in a box (crudely speaking)?

[selfAdjoint]

They have been able to "image" single atoms with the scanning tunneling electron microscope. These images are essentially averaged over short periods of time. Whether you call that "seeing" or not is up to you. If you are moved to be critical, recall that our natural seeing is more problematical, according to experimental psychologists, than we like to suppose.

[LURCH]

Agreement. We only "see" anything by bombarding it with photons and then measuring how those photons impact us and infering what they must have been up to before reaching us. If that's seeing, then I would say the STM constitute sight as well.

[Claude Bile]

We could not see an atom with an optical microscope (i.e. gauge it's size), even if the magnification were sufficient due to scattering effects, the atom would appear larger than it actually is.

While this is obviously difficult experientally, a similar effect is seen when observing fluroesecent nanoparticles under a microscope. Even though they are only 200 nm in diameter (Measured with an SEM) they appear to be at least a couple of microns wide under a microscope.

It is the scattering cross section of a particle rather than its physical size that determines how photons scatter off it and thus how the particle would appear under a microscope.

Claude.

[Gonzolo]

With electron microscopes (TEM), we can see images of certain crystal atomic planes seperated by only about 10-15 nm. (100-150 A). This size corresponds to an axis of the crystal's unit cell.

[Claude Bile]

Agreed, though I was referring to purely optical devices. With the aid of SEM, STM and NSOM technology, we can substantially improve our resolution.

Claude.

[misogynisticfeminist]

One more question: If we see the atom or maybe sub-atomic particles someday, would we see probability clouds or nice, rounded spheres? Or does the act of seeing cause wavefunction collapse ? Would quantum wierdness be apparent if we have the technology to see atoms and all..?

[Gonzolo]

How's this for relevance :

http://story.news.yahoo.com/news?tmpl=story2&u=/040921/480/tnkv60209210713&e=7

Quote : "Researchers Say Microscope Can See Atoms"

[Seiya Hilendith]

I believe, actually, and don't get me wrong, because I don't know if this has been said, that an atom is smaller than the minimal wavelength of visible light, which is violet. I'd say the scattering effect is comparable with a black pixel in a square of white being smoothed over to gray scales. That's why you cannot see one optically