Difference Between Bosons and Fermions

The key difference between bosons and fermions is that bosons have integer spin whereas fermions have half-integer spin.

All the particles we observe in nature comes in two types as bosons and fermions. We can divide the particles into these two groups based on the spin of the particles. Therefore, we call it “spin classification”. All particles have a spin or “intrinsic angular momentum”.

1. Overview and Key Difference
2. What are Bosons
3. What are Fermions
4. Side by Side Comparison – Bosons vs Fermions in Tabular Form
5. Summary

What are Bosons?

Bosons are a type of particles with integer spin. Therefore, these particles are not constrained by the Pauli exclusion principle. We can describe the energy distribution of these particles using Bose-Einstein statistics.

Figure 01: Symmetric Wave Function of Bosons

Some examples of bosons include fundamental particles such as photons, gluons, etc. It includes both elementary particles and composite particles, i.e. mesons. One important characteristic of these particles is that they do not restrict the number of particles that occupy the same quantum state. Bosons are called “force carriers” due to this reason. Moreover, they act as the glue that holds the matter together. Moreover, the wave function, which describes a collection of bosons, must be symmetric with respect to the exchange of identical particles.

What are Fermions?

Fermions are a type of particles with half-integer spin. Therefore, they are constrained by the Pauli exclusion principle. Unlike bosons, two fermions cannot occupy the same quantum state at the same time. If multiple fermions have the same spatial probability distribution, then at least the spin of each fermion is different from each other. Moreover, fermions are particles that make up the matter.

Figure 02: Antisymmetric Wave Function of Fermions

Examples for fermions include electrons, protons and neutrons. Furthermore, the wave function that describes a collection of fermions must be antisymmetric with respect to the exchange of identical particles.

What is the Difference Between Bosons and Fermions?

Bosons and fermions are two groups of particles. The key difference between bosons and fermions is that bosons have an integer spin whereas fermions have a half–integer spin. Furthermore, the wave function of bosons is symmetric while the wave function of fermions is antisymmetric.

Moreover, bosons particles are not constrained by the Pauli Exclusion Principle, but fermions are. Apart from that, at the same quantum state, two boson particles can occupy at the same time, but fermions cannot occupy the same quantum state at the same time. So, this is also a significant difference between bosons and fermions. Some examples for bosons include photons, gluons, helium atoms, etc. while for fermions examples include electrons, protons, quarks, neutrons, etc.

Below info-graphic shows more descriptions regarding the difference between bosons and fermions.

Summary – Bosons vs Fermions

All the particles we know can be divided into two groups as bosons and fermions, based on the spin of particles. The key difference between bosons and fermions is that bosons have integer spin, whereas fermions have a half-integer spin.

Reference:

1.“Spin Classification.” Spin Classification of Particles, Available here.

Image Courtesy:

1. “Symmetricwave2” By TimothyRias – Own work (CC BY 3.0) via Commons Wikimedia
2. “Asymmetricwave2” By TimothyRias – Own work (CC BY 3.0) via Commons Wikimedia