Protons and neutrons form an atomic nucleus without "touching" each other in the conventional sense of solid objects making physical contact. The behavior of particles at the subatomic level is governed by quantum mechanics, which operates differently from our everyday macroscopic experience.
In an atomic nucleus, protons and neutrons are held together by a strong nuclear force called the residual strong force or the strong nuclear force. This force is one of the fundamental forces of nature, along with gravity, electromagnetism, and the weak nuclear force. The strong nuclear force is responsible for binding protons and neutrons together, overcoming the repulsive electromagnetic force between the positively charged protons.
The strong nuclear force acts over extremely short distances, on the order of femtometers (10^−15 meters). It is a short-range force that diminishes rapidly with distance. It keeps the protons and neutrons in close proximity to each other, forming a tightly bound nucleus.
In quantum mechanics, particles are described by wave functions, which represent the probability distribution of finding the particle at different locations. The wave functions of protons and neutrons in the nucleus overlap, allowing them to interact through the strong nuclear force. However, they do not occupy specific, well-defined positions like solid objects in classical physics.
It's important to note that the concept of "touching" at the atomic scale does not have the same meaning as in everyday experience. Quantum mechanics describes particles as both particles and waves, exhibiting characteristics of both. The behavior of subatomic particles is better understood through the principles of quantum mechanics rather than classical notions of touch or physical contact.