Subatomic particle that is part of the nucleus of the Atomo. The proton has a positive charge and a mass 1,840 times greater than that of the electron (which, by convention, is equal to 1). In a stable atom, the number of protons in the nucleus is equal to that of electrons. The proton and the neutron are also called nucleons.

The nucleus of the hydrogen atom is formed by a single proton. The mass of a proton is 1.6726 × 10-27 kg, approximately 1,836 times that of the electron. Therefore, the mass of an atom is concentrated almost exclusively in its nucleus.

The proton has an intrinsic angular momentum, or spin, and therefore a magnetic moment. On the other hand, the proton complies with the exclusion principle. The atomic number of an element indicates the number of protons in its nucleus, and determines which element it is.

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ProtostarProton-proton (cycle)