The smallest possible size for an atom is determined by its fundamental constituents, which are protons, neutrons, and electrons. Atoms are typically classified as the basic building blocks of matter. However, atoms are not indivisible and can be further divided into subatomic particles.
Protons and neutrons are found in the nucleus of an atom, while electrons orbit around the nucleus in specific energy levels. The size of an atom is primarily determined by the extent of the electron cloud, which represents the region where electrons are most likely to be found. It is important to note that the electron cloud does not have a sharp boundary, and the electrons exist in a state of probability distribution rather than as distinct particles with defined positions.
The limit to how small an atom can be divided is governed by the concept of subatomic particles. Protons and neutrons, once thought to be fundamental particles, are now known to be composed of smaller particles called quarks. Electrons are currently considered fundamental particles with no known substructure.
The study of subatomic particles and their interactions is a field of research known as particle physics. Scientists use powerful particle accelerators and detectors to probe the smallest scales of matter. While the concept of a fundamental limit to the size of an atom is not yet known, current scientific understanding suggests that quarks and electrons are point-like particles without any internal structure.
As for why we have not observed anything smaller than subatomic particles, it is mainly due to technological limitations. To explore the subatomic realm, scientists require extremely high-energy experiments and advanced detection methods. Currently, our technological capabilities have not reached a level where we can directly observe or manipulate particles smaller than those already known. However, ongoing research in particle physics aims to uncover new insights into the fundamental nature of matter and potentially discover new particles or phenomena beyond our current understanding.