A stable subatomic particle in the baryon family having a mass of 1.672 × 10
-24 grams (1,836 times that of the electron) and a positive electric charge of approximately 1.602 × 10
-19 coulombs. Protons make up part of the nucleus of all atoms except hydrogen, whose nucleus consists of a single proton. In neutral atoms, the number of protons is the same as the number of electrons. In positively charged atoms, the number of protons is greater than the number of electrons, and in negatively charged atoms electrons outnumber protons. Protons are believed to be composed of two up quarks and one down quark. See Table at
subatomic particle.