*Fermions* constitute the second of the two main categories of sub-[[Atom|atomic]] particles in physics (the other category being [[Boson|bosons]]). They have half-integer [[Spin|spin]]. For example, the electron is a fermion and has spin 1/2. Fermions must obey the **Pauli exclusion principle**, which means **no two fermions can occupy the same quantum state** at once. This exclusiveness is crucial for forming stable matter (e.g., distinct electron shells in atoms). It also gives us an understanding of how the periodic system of elements is structured. Other examples of fundamental fermions include quarks (which make up [[Proton|protons]] and [[Neutron|neutrons]]) and neutrinos. >[!read]- Further Reading >- [[Electron]] >- [[Boson]] >[!ref]- References