Half-integer spin fermions are constrained by the Pauli exclusion principle whereas integer spin bosons are not. The spin classification of particles determines the nature of the energy distribution in a collection of the particles. Back Fermions Fermions are particles which have half-integer spin and therefore are constrained by the Pauli exclusion principle . Particles with integer spin are called bosons .
Fermions incude electrons , protons , neutrons .
The wavefunction which describes a collection of fermions must be antisymmetric with respect to the exchange of identical particles, while the wavefunction for a collection of bosons is symmetric. The fermion nature of electrons also governs the behavior of electrons in a metal where at low temperatures all the low energy states are filled up to a level called the Fermi energy. This filling of states is described by Fermi-Dirac statistics . Back Bosons Bosons are particles which have integer spin and which therefore are not constrained by the Pauli exclusion principle like the half-integer spin fermions . The energy distribution of bosons is described by Bose-Einstein statistics .