well you cant see them in open air, its literally impossible.
Because a law of physics states that no neutrons can occupy more than a single point in space, which also means that no two neutrons can occupy the same point in space time, since electrons and protons are derivatives of neutrons, it applies to them too.
But photons, light particles, do not have to comply with that rule, that is why they can pass through seemingly solid objects that are thin enough, because they can occupy a point in space occupied by a neutron or neutron derivative. But it takes away some of the energy of the photon, and when the resistance of passing through the object is too much it will simply bounce off, that is what you see.
But many of the atoms with small atomic numbers including oxygen, CO2, nitrogen, and more have very little resistance against the photons while the ones with larger amounts are very resistant, and of course there are abnormal ones that dont follow the general rule. But that general rule applies to solids, most gases since the atoms are very spaced out resist photons very little.
But the fact is you cannot see any individual atoms simply because those ones in the air have negligible amounts of resistance and you simply cannot see them because when the photon hits any atom, it would simply go through the atom, you need for it to bounce off to get an image.
