nucleon

(noun)

One of the subatomic particles of the atomic nucleus (i.e., a proton or a neutron).

Related Terms

Examples of nucleon in the following topics:

  • Binding Energy and Nuclear Forces

    • The component parts are neutrons and protons, which collectively are called nucleons.
    • Conversely, energy is released when a nucleus is created from free nucleons or other nuclei—known as the nuclear binding energy.
    • It is the attractive force that binds together particles known as quarks (to form the nucleons themselves).
    • Similarly, even though nucleons are made of quarks in combinations which cancel most gluon forces (they are "color neutral"), some combinations of quarks and gluons leak away from nucleons in the form of short-range nuclear force fields that extend from one nucleon to another nucleon in close proximity.
    • A model of the atomic nucleus showing it as a compact bundle of the two types of nucleons: protons (red) and neutrons (blue).

  • Conservation of Nucleon Number and Other Laws

    • Through radioactive decay, nuclear fusion and nuclear fission, the number of nucleons (sum of protons and neutrons) is always held constant.
    • In physics and chemistry there are many conservation laws—among them, the Law of Conservation of Nucleon Number, which states that the total number of nucleons (nuclear particles, specifically protons and neutrons) cannot change by any nuclear reaction.
    • Chain reactions of nuclear fission release a tremendous amount of energy, but follow the Law of Conservation of Nucleon Number.
    • Finally, nuclear fusion follows the Law of Conservation of Nucleon Number.
    • Thus, the number of nucleons before and after fission and fusion is always constant.

  • Alpha Decay

    • Alpha decay is by far the most common form of cluster decay, in which the parent atom ejects a defined daughter collection of nucleons, leaving another defined product behind (in nuclear fission, a number of different pairs of daughters of approximately equal size are formed).
    • In theory it can occur only in nuclei somewhat heavier than nickel (element 28), in which overall binding energy per nucleon is no longer a minimum and the nuclides are therefore unstable toward spontaneous fission-type processes.

  • Beta Decay

    • Beta decay does not change the number of nucleons, A, in the nucleus; it changes only its charge, Z.