We know very well that all substances are composed of atoms - this is the smallest possible amount of any chemical element. The word "atom" comes from the Greek word "ἄτομος", which literally translates from ancient Greek as "indivisible" - something that can no longer be divided. Later, however, it turned out that atoms are not at all indivisible, but consist of a nucleus and electrons revolving around it. But it turned out that this is not the limit….
Soon, other elementary constituent particles like quarks were discovered, even the integrity of electrons, which could presumably be split into holons, spinons and orbitons, were questioned.
The "first bricks" of matter are so small that conclusions about their existence were made indirectly - through various experiments and mathematical calculations, but it would be very cool if we could see them with our own eyes, as we see microorganisms in a drop of water under a microscope. However, why not? It would seem that you just need to take a more powerful microscope and you can examine anything. Alas, no matter how powerful an optical microscope is, you cannot get with it a picture of not only an atom, but also a molecule.
To see an object, it must be illuminated with a beam of light, and the light must be reflected from its various parts and hit the retina. However, it is impossible to illuminate a certain atom due to the very way of interaction of photons with an atom. Most of the photons will simply fly through the atom, and if some photon is reflected back into the microscope eyepiece, then this will obviously not be enough. And in general, the visible light used in optical microscopes has a wavelength of the order of 400-700 nanometers, while the size of an atom is about 0.1 nanometer, so it is simply pointless to illuminate the atom with it.
But what if, instead of visible light, you use something else, for example, gamma radiation or a directed electron beam, which under certain conditions can behave like a wave with a length comparable to the size of elementary particles? That is, can an atom be seen through an electron microscope?
Yes and no. Yes, because photographs of atoms do exist, no - because the resulting image does not so much reflect the true appearance of the atom as it creates an accessible visualization. However, photographs of atoms taken by even the most powerful and accurate electron microscopes do not reveal their structure.
The photo shows the sulfur atoms and the place where one atom is missing. (c) David A. Muller et al. Nature, 2018.
First, most of the atom is empty space. The distances between the nucleus and the electrons on a scale are so huge that if you enlarge the nucleus to the size of an apple, then the electrons will revolve around it in an orbit with a radius of about a kilometer. This means that the particles that make up an atom simply would not fit into the field of view.
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Second, the Heisenberg uncertainty principle prevents us from considering the details. The location of the electron in the atom is determined as probable, at some moment of time it can be in one or another place. Therefore, in the photographs obtained, the atoms are seen as blurred balls-clouds formed by the rapidly changing orbit of electrons.
And finally, a funny video from IBM "The Boy and His Atom". Engineers at IBM used a scanning tunneling microscope to move carbon monoxide molecules (two atoms stacked on top of each other). Thanks to this, it was possible to shoot a video with objects so small that they can only be seen at a magnification of 100 million times.