If protons are the identity badge of an atom, neutrons are its silent partners. Sitting in the nucleus right alongside protons, neutrons carry no electrical charge — they are neutral, which is exactly where their name comes from. Despite having no charge, neutrons play a crucial role: they act as nuclear glue. Without neutrons, the positively charged protons in a nucleus would repel each other and fly apart. Neutrons provide extra strong nuclear force attraction without adding electrical repulsion, stabilizing the nucleus.
James Chadwick discovered the neutron in 1932, more than a decade after the proton was identified. Scientists had long suspected that something else existed in the nucleus because atoms were heavier than their proton count alone would explain. Chadwick bombarded beryllium with alpha particles and detected a mysterious radiation that could knock protons out of paraffin wax. He showed this radiation consisted of neutral particles with a mass close to that of a proton. His discovery earned him the 1935 Nobel Prize in Physics and filled in a critical missing piece of atomic theory.
The number of neutrons in an atom can vary without changing the element — and this gives rise to isotopes. Carbon-12 has 6 neutrons, carbon-13 has 7, and carbon-14 has 8, but all three are still carbon because they all have 6 protons. This variation has enormous practical consequences. Carbon-14 is radioactive and is used in radiocarbon dating to determine the age of ancient artifacts. Certain uranium isotopes fuel nuclear reactors, while others do not. In medicine, specific isotopes are used as tracers in diagnostic imaging. Neutrons, though electrically silent, have a remarkably loud impact on our world.