By William Hirsch Updated Aug 30, 2022
Protons are subatomic particles that, along with neutrons, form the nucleus of an atom. While slightly lighter than neutrons, a proton is about 1,836 times heavier than an electron, with a mass of 1.6726 × 10⁻²⁷ kg. Despite being a composite particle, its positive electric charge is fundamental to atomic structure.
Protons are not elementary; they consist of three valence quarks bound by the strong force, a fact that underlies their stability and interactions.
The positive charge of protons holds the nucleus together through electrostatic attraction and creates the electric field that keeps electrons in orbit. The count of protons—denoted by the atomic number (Z)—uniquely identifies each chemical element.
In high‑energy physics, proton beams are accelerated to relativistic speeds and collided to probe fundamental forces and particles. CERN’s Large Hadron Collider (LHC) uses powerful superconducting magnets to guide protons around a 27‑kilometre ring before head‑on collisions, revealing sub‑nuclear structures and testing theoretical models. Such experiments also aim to recreate the quark‑gluon plasma that existed shortly after the Big Bang.
Within stellar cores, protons undergo nuclear fusion at temperatures around 1 million °C. Fusion merges lighter nuclei into heavier ones, releasing energy because the final mass is less than the sum of the initial masses. Einstein’s mass‑energy equivalence (E = mc²) explains this energy release, which powers the Sun and other stars.
