proton

A proton is a type of baryon that has an electric charge of +1 and is stable. (A baryon is a hadron, i.e., a composite particle, that is made up of three quarks.) Protons are subject to the strong force, the force which draws together protons and neutrons to form an atomic nucleus. The nucleus of all elements include protons, but the simplest/most-common hydrogen nucleus consists of just a proton, and ionized hydrogen is just protons. At room-temperature velocities, protons are merely hydrogen and not dangerous, but higher-velocity protons found in the solar wind and cosmic rays are a danger to humans and to equipment in outer space.

Protons were created very soon after the Big Bang when the temperature dropped sufficiently that quarks combined into protons and neutrons. Radioactive decay sometimes converts a proton within a nucleus to a neutron or vice versa.