Nucleon
A nucleon is a collective term for protons and neutrons, the particles that make up the atomic nucleus. These subatomic particles are themselves composite particles, meaning they are composed of smaller, fundamental particles called quarks.
Properties:
- Constituents of the Nucleus: Nucleons are the primary building blocks of atomic nuclei, held together by the strong nuclear force.
- Baryons: Nucleons are classified as baryons, a type of hadron (particles made of quarks). Baryons are characterized by having three valence quarks.
- Spin: Both protons and neutrons have an intrinsic angular momentum known as spin, with a value of 1/2 (expressed in units of ħ, the reduced Planck constant). This spin contributes to the overall spin of the nucleus.
- Mass: Protons and neutrons have slightly different masses. The proton has a mass of approximately 1.67262 × 10-27 kg, while the neutron has a slightly larger mass of approximately 1.67493 × 10-27 kg.
- Electric Charge: Protons carry a positive electric charge (+1e, where e is the elementary charge), while neutrons are electrically neutral (charge of 0).
- Strong Nuclear Force: Nucleons interact through the strong nuclear force, which is mediated by particles called gluons. This force overcomes the electrostatic repulsion between protons in the nucleus.
Significance:
The number of protons (atomic number) determines the element, while the number of neutrons affects the isotope of that element. The strong interaction between nucleons is crucial for the stability of atomic nuclei. Understanding the properties and interactions of nucleons is fundamental to nuclear physics and related fields, such as nuclear chemistry and nuclear engineering.
Quark Composition:
- Proton: Composed of two up quarks (u) and one down quark (d) (uud).
- Neutron: Composed of one up quark (u) and two down quarks (d) (udd).
The interaction between these quarks, mediated by gluons, is described by quantum chromodynamics (QCD).