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Facts about Protons for Kids


The proton is a subatomic particle with the symbol p or p+ and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom.

  • The name proton was given to the hydrogen nucleus by Ernest Rutherford in 1920, because in previous years he had discovered that the hydrogen nucleuscould be extracted from the nuclei of nitrogen by collision, and was thus a candidate to be a fundamental particle and building block of nitrogen, and all other heavier atomic nuclei.
  • In the modern standard model of particle physics, the proton is a hadron, composed of quarks.
  • Prior to that model becoming a consensus in the physics community, the proton was considered a fundamental particle.
  • In the modern view, a proton is composed of two up quarks and one down quark, with the rest mass of the quarks thought to contribute only about 1% of the proton’s mass.
  • The free proton is a stable particle that has not been observed to break down spontaneously to other particles.
  • Free protons are found naturally in a number of situations in which energies or temperatures are high enough to separate them from electrons, for which they have some affinity.
  • Protons also result from the radioactive decay of free neutrons, which are unstable.
  • When free hydrogen atoms react with each other, they form neutral hydrogen molecules (H2), which are the most common molecular component of molecular clouds in interstellar space.
  • Such molecules of hydrogen on Earth may then serve as a convenient source of protons for accelerators and other hadron particle physics experiments that require protons to accelerate, with the most powerful and noted example being the large hadron collider.
  • Two terms are used in referring to the mass of the quarks that make up protons: Current quark mass refers to the mass of a quark by itself, while constituent quark mass refers to the current quark mass plus the mass of the gluon particle field surrounding the quark.
  • The most recent calculations claim that the mass is determined to better than 4% accuracy, even to 1% accuracy.
  • However, since July 5, 2010, an international research team has been able to make measurements involving a proton and a negatively-charged muon.
  • The Apollo Lunar Surface Experiments Packages (ALSEP) determined that more than 95% of the particles in the solar wind are electrons and protons, in approximately equal numbers.
  • Because the Solar Wind Spectrometer made continuous measurements, it was possible to measure how the Earth’s magnetic field affects arriving solar wind particles.
  • Protons also occur in from extrasolar origin in space, from galactic cosmic rays, where they make up about 90% of the total particle flux.