So far as I know, even near-field optical microscopes are unable to
form images of atoms which come cloes to being pictures in the ordinary
sense. However, other types of microscopes regularly form images of
atoms. For exampls, scanning tunneling microscopes (STMs) work by
seeing how close they have to get to some surface to run a current
through them at some voltage. When there's an atom sitting on the
surface, it shows up as a lump in the STM position. Even the atoms in
the surface show up as a regular pattern in the image. This technique
is entirely routine.
There are many, many other ways in which the theory of atoms is
confirmed. These range from detailed spectroscopy to the quantitative
confirmation of predictions for the thermal properties of gases. The
STM and other images are just the icing on a very big cake.
Mike W.
(published on 10/22/2007)