The nucleus of an atom is primarily made up of two types of particles: protons and neutrons. Together, these particles are known as nucleons.
Protons are positively charged particles, and their number in the nucleus determines the atomic number of the element, which identifies what element it is. For example, hydrogen has one proton, while carbon has six protons.
Neutrons, on the other hand, have no electric charge and contribute to the mass of the atom. The number of neutrons can vary within atoms of the same element, resulting in different isotopes. For instance, carbon has three commonly known isotopes: carbon-12, carbon-13, and carbon-14, which differ in the number of neutrons.
Together, protons and neutrons are held tightly in the nucleus by the strong nuclear force, which is one of the four fundamental forces of nature. This force is crucial for the stability of the nucleus, counteracting the repulsive electromagnetic force between the positively charged protons.