nucleons

Nucleons are the collective term for the subatomic particles that compose atomic nuclei, primarily protons and neutrons. These particles are classified as baryons, which are a type of fermion, meaning they follow the Pauli exclusion principle and contribute to the overall mass and charge of an atom.

Protons are positively charged particles, with a charge equal in magnitude but opposite in sign to that of electrons. They are stable and serve as a key factor in determining the elemental identity of an atom. The number of protons, known as the atomic number, defines the chemical element. Neutrons are electrically neutral particles that reside within the nucleus alongside protons. Their primary role is to add to the nuclear mass and contribute to nuclear stability by offsetting electrostatic repulsion between positively charged protons.

Nucleons are held together in the nucleus by the strong nuclear force, one of the four fundamental forces of nature. This force is attractive and significantly stronger than electromagnetic repulsion at very short distances, enabling protons and neutrons to coexist within the nucleus despite their electrostatic repulsion. The interactions among nucleons are described by quantum chromodynamics, which accounts for the behavior of the underlying quarks and gluons involved.

The mass of nucleons is approximately 938 MeV/c² for protons and 939 MeV/c² for neutrons, accounting for most of the atom’s mass. Isotopes are variants of elements distinguished by differing numbers of neutrons, affecting nuclear stability and properties. Understanding nucleons is fundamental to nuclear physics, cosmology, and various applications including nuclear energy and medical imaging.