Bosons are those particles that have an integer spin measured in the units of h-bar (spin = 0, 1, 2...).

The following are bosons:

• The carrier particles related to all the fundamental interactions
• Composite particles with even numbers of fermion constituents (such as mesons)

The nucleus of an atom is a fermion or boson depending on whether the sum of the number of protons and neutrons is odd or even. This property explains the strange behavior of very cold helium, which is a superfluid (meaning it has no viscosity, among other things) because its nuclei are bosons and may pass through each other.

quarks No, try again. protons No, try again. photons Correct! They are bosons. electrons No, try again.