Baryons
All known baryons are made of three valence quarks, so they are fermions (i.e. they have odd half-integral spin because they have an odd number of quarks). As quarks possess baryon number B = 1⁄3, baryons have baryon number B = 1. The best-known baryons are the proton and the neutron.
One can hypothesise baryons with further quark–antiquark pairs in addition to their three quarks. Hypothetical baryons with one extra quark–antiquark pair (5 quarks in all) are called pentaquarks. Several pentaquark candidates were found in the early 2000s, but upon further review these states have now been established as non-existent. (This does not rule against pentaquarks in general, only the candidates put forward). No evidence of baryon states with even more quark–antiquark pairs has been found either.
Each type of baryon has a corresponding antiparticle (antibaryon) in which quarks are replaced by their corresponding antiquarks. For example: just as a proton is made of two up-quarks and one down-quark, its corresponding antiparticle, the antiproton, is made of two up-antiquarks and one down-antiquark.
Read more about this topic: Hadron