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Proton
From Citizendium, the Citizens' Compendium
A proton is a subatomic-particle with a mass of 1.672 621 58 × 10−27 kg, a charge equal to the elementary charge of 1.602 176 462 × 10−19 coulomb and a spin of 1/2. Protons are one of the three fermions which make up most of the matter we deal with every day. They along with neutrons form the nucleus of every atom. They were briefly believed to be an fundamental particle however the rapid discovery of other particles in middle of the twentieth century disproved this theory. They are now known to be composed of two down quarks and one up quark. Protons are the lightest and most stable member of the baryon family.
Introduction
Protons, along with neutrons and electrons are the 3 building blocks of atoms, and are directly responsible for nearly 50% of the matter humans encounter on a daily basis.
History
The Proton was first proposed by Ernest Rutherford who discovered that there was a very dense positively charged center to an atom.
Structure
According to the Standard Model protons are composed of 3 quarks, two up quarks and one down quark. These combine to give it its charge and spin. These three quarks are held together by the strong force, the energy of these bonds is responsible for much of a protons mass.
