Protons
Protons
Protons (/ˈproʊ.tɒn/) are subatomic particles, symbol p or p+, with a positive electric charge of +1e elementary charge and a mass slightly less than that of a neutron. Protons and neutrons, each with masses of approximately one atomic mass unit, are collectively referred to as "nucleons".
Etymology
The term "proton" comes from the Greek word "protos", meaning "first". This name was given by physicist Ernest Rutherford in 1920, who first discovered the existence of protons.
Properties
Protons are composed of two up quarks, one down quark, and the gluons that mediate the forces "binding" them together. The rest masses of quarks contribute only about 1% of a proton's mass. The remainder of a proton's mass is due to quantum chromodynamics binding energy, which includes the kinetic energy of the quarks and the energy of the gluon fields that bind the quarks together.
Interaction
Protons are spin-½ fermions and are subject to the Pauli exclusion principle. They are a necessary part of atomic nuclei. Protons also act as stable building blocks of the universe and determine the chemical properties of every atom. They are observed in the interactions of cosmic rays.
Related Terms
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