The concept of what an atom "looks" like has evolved over time as our understanding of atomic structure has advanced. Atoms are incredibly small, on the scale of nanometers (10^-9 meters), making them impossible to directly observe using traditional optical microscopes.
Our current understanding of atomic structure is based on various experimental evidence and theoretical models. The most widely accepted model is the electron cloud or quantum mechanical model, which describes the distribution of electrons in terms of probability densities and orbitals.
According to this model, atoms consist of a nucleus at the center, composed of protons and neutrons. The nucleus is surrounded by a cloud of electrons that occupy specific energy levels or orbitals. These orbitals represent regions in space where electrons are likely to be found.
While we cannot "see" atoms in the same way we see macroscopic objects, we have indirect evidence and experimental techniques that allow us to infer their existence and behavior. For example, techniques such as scanning tunneling microscopy (STM) and atomic force microscopy (AFM) can provide images of the surfaces of materials at the atomic scale by detecting interactions between atoms and a scanning probe.
Additionally, advancements in X-ray crystallography, electron microscopy, and spectroscopy have provided valuable insights into atomic structures and their arrangement in molecules and materials. These techniques allow scientists to indirectly observe the positions and arrangements of atoms in a variety of substances.
It's important to note that while we have developed detailed models and experimental techniques to understand atomic structure, our understanding is continually evolving as new technologies and theoretical advancements emerge.