Oxygen-16 Nucleus

The neutron is the electrically neutral baryon that, together with the proton, builds atomic nuclei. A free neutron decays by beta-minus decay into a proton, an electron, and an electron antineutrino in about 15 minutes, while neutron-rich matter can persist inside neutron stars.

Object class

Baryon

The proton is the positively charged particle that gives every atomic nucleus its identity. Less than 1% of a proton’s mass comes from the masses of its quarks; almost all of the rest comes from the energy of quarks and gluons bound by the strong force.

Object class

Baryon

Hydrogen is the universe’s simplest and most common atom. Most hydrogen nuclei were forged in the first minutes after the Big Bang, and neutral hydrogen atoms emerged only after the universe cooled enough for electrons and protons to combine about 380,000 years later.

Object class

Atom

Composition

1 proton, 1 electron