Proton
A positively charged subatomic particle found in the atomic nucleus, carrying a charge of +1 elementary unit.
Formula / equation
m_p = 1.6726 × 10⁻²⁷ kg
Unit
u
In depth
With a mass of 1.00728 u, the proton is a baryon composed of two up quarks and one down quark. Its count in the nucleus defines the element and sets the nuclear charge that binds the electron cloud. A bare proton is simply a hydrogen ion, H⁺, and is the species transferred in every Brønsted acid–base reaction.
Examples in the real world
The single proton in a hydrogen nucleus; the 26 protons that make an atom iron rather than manganese.