The main difference between protons and neutrons is that protons carry a positive charge, while neutrons are neutral (having no charge). Both protons and neutrons are found in the atomic nucleus and contribute to the atom's mass. Protons determine the atomic number, defining the identity of the element, while neutrons contribute to the stability of the nucleus. The number of protons in an atom defines its chemical properties, whereas the number of neutrons can vary, resulting in the formation of different isotopes of an element. This distinction is fundamental in understanding atomic structure and behavior.