What are nucleons?

Nucleons are either protons (positively charged subatomic particles) or neutrons (uncharged subatomic particles) , in the practices of chemistry or physics. They are known for their role as making up an atomic nucleus. The number of nucleons in a nucleus defines an isotope's mass or nuclei number.

Nucleons were thought to be elementary particles, until the 1960s, not made up of smaller parts. Now they are known to be composite particles, made of three quarks linked together by the so-called strong interaction. The interaction between two or more nucleons is called internucleon interaction or nuclear force, which is also ultimately caused by the strong interaction.

Nucleons sit at the border where particle physics and nuclear physics overlap. Particle physics, particularly quantum chromodynamics, provides the fundamental equations that explain the properties of quarks and of the strong interaction. These equations explain quantitatively how quarks can bind together into protons and neutrons.