Chapter 29: Nuclear Physics
29.D: Subatomic Particles
- Subatomic Particle
- A particle smaller than an atom.
- Elementary Particle
- A subatomic particle that is not made up of smaller particles.
- Composite Particle
- A subatomic particle that is made up of other subatomic particles.
- Antiparticle
- A particle having the same mass and spin as its corresponding particle but having other characteristics that are opposite.
- Quark
- An elementary subatomic particle used to make up hadrons.
- Standard Model
- The classification system for subatomic particles that provides descriptions of three of the four fundamental forces.
Early Evidence of More Subatomic Particles
- Wolfgang Pauli suggested the existence of another particle in 1931.
- Fermi named this proposed particle the neutrino.
- Neutrinos were finally detected in 1956.
Nuclear Building Blocks
- Protons and neutrons are composite particles.
- Electrons are elementary particles.
- Rule 1: Every reaction will happen at some time unless prohibited by a conservation law.
- Rule 2: Every particle has an antiparticle.
Subatomic Particle Zoo
- Physicists are compelled to classify subatomic particles.
- Fermions include the leptons and quarks.
- Bosons are the other major group of elementary particles.
- Elementary fermions and bosons can combine to form hadrons.
- Composite fermions form baryons, including protons and neutrons.
- Composite bosons form mesons.
- Only a few of the subatomic particles are stable.
Quarks
- There are six kinds (flavors), each given a whimsical name.
- Every quark has an associated antiquark.
- Quarks have fractional charges.
- Quarks combine to form hadrons.
- Quarks do not exist individually; they exist only inside hadrons. This is called quark confinement.
- The forces that hold quarks tightly are described by their color charge.
Questions for Students
- Define subatomic particle, elementary particle, and composite particle.
- What is an antiparticle and how does it relate to its corresponding particle?
- Describe the role of quarks in the structure of hadrons.
- What is the standard model and what does it describe?
- Explain the concept of quark confinement and color charge.