Particles in quantum mechanics are categorized into two principal types based on their intrinsic angular momentum, known as spin.
- Fermions: Particles characterized by half-integer spin values (\(\frac{1}{2}, \frac{3}{2}, \frac{5}{2}, ...\)) in units of \(\hbar\). These particles adhere to the Pauli exclusion principle, forbidding identical fermions from occupying the same quantum state concurrently. Common examples include electrons, protons, and neutrons, all possessing a spin of 1/2.
- Bosons: Particles possessing integer spin values (\(0, 1, 2, ...\)) in units of \(\hbar\). They are not subject to the Pauli exclusion principle. Examples include photons (spin 1) and Higgs bosons (spin 0).
The stated half-integer spin value is \(1/2\).
