Fermions are the building blocks of matter, distinguishing them from bosons, which mediate forces.

Fermions are fundamental particles that obey Fermi-Dirac statistics and follow the Pauli exclusion principle, meaning no two identical fermions can occupy the same quantum state simultaneously.

Two Types of Fermions

Fermions are classified into two main categories:

Quarks – The constituents of protons and neutrons.

Leptons – Includes electrons, muons, and neutrinos.

Each of these particles has an antiparticle counterpart, such as the positron, the antimatter version of the electron.

Fermions in the Standard Model

The Standard Model of Particle Physics recognizes 24 different fermions:

Fermion AntiMatter Particles

Each of the above fermions has a corresponding antiparticle:

12 Antiparticles

Anti-up quark, anti-down quark, anti-strange quark, anti-charm quark, anti-bottom quark, anti-top quark,

Electron antineutrino, muon antineutrino, tau antineutrino,

Positron, antimuon, antitau.

Interactions and Composite Fermions

Fermions participate in gravitational, electromagnetic, weak nuclear, and strong nuclear forces.

Some fermions, like protons and neutrons, are made up of quarks and are known as composite particles.

Composite fermions (such as hadrons, nuclei, and atoms) can be bosons or fermions depending on their constituents.

Because of the relation between spin and statistics, a particle containing an odd number of fermions is itself a fermion.

It will have half-integer spin.

The Importance of Fermions

Why are fermions important to our understanding of the Universe?

Fermions are essential for the structure of matter.

Their behaviour under Quantum Mechanics explains:

• Atomic structure: Electrons form distinct energy levels due to the Pauli exclusion principle.
• Nuclear interactions: Quarks combine to form protons and neutrons, which make up atomic nuclei.
• Condensed matter physics: The behaviour of electrons in solids leads to phenomena like superconductivity and Fermi liquid theory.