A neutral nuclear particle with mass slightly greater than a proton, discovered by Chadwick in 1932.
Practise Atomic Structure & Periodicity All Atomic Structure & Periodicity topics
The neutron is a neutral nuclear particle with mass about 1.675 x 10^-27 kg, slightly larger than the proton. James Chadwick discovered it in 1932 by observing radiation that could knock protons out of paraffin wax. Neutrons add strong-force attraction within the nucleus without adding electrical repulsion, so they stabilise nuclei and help determine the isotope. A free neutron is unstable and decays with a half-life of about 10 minutes, but neutrons bound in stable nuclei do not decay. Neutrons are also essential to nuclear fission, because they can split heavy nuclei.
Key ideas: The neutron is neutral with mass 1.675 x 10^-27 kg (1.0087 u), slightly heavier than the proton (discovered by Chadwick, 1932). Number of neutrons N = A - Z. Neutrons add mass and nuclear stability without changing chemistry much; stable light nuclei have N close to Z, heavy ones need N about 1.5 times Z.
Common mistakes and connections: Students think neutrons change the chemical element, but they only define the isotope. A free neutron decays with a half-life of about 10 minutes, which most forget. Neutrons drive nuclear fission chain reactions and explain the isotopes and the band of stability.
Neutrons add mass without charge; light stable nuclei have about equal neutrons and protons, while heavy nuclei like lead-208 need many more. The interactive lesson shows this as a live animation or chart.
Uranium-235 absorbs a neutron and splits, releasing more neutrons that can continue a chain reaction.
A neutral nuclear particle with mass slightly greater than a proton, discovered by Chadwick in 1932.
Neutron is a beginner topic in Atomic Structure & Periodicity. It needs no earlier chemistry lessons and is a good starting point.
Study these earlier topics in Atomic Structure & Periodicity first: Dalton's Atomic Theory, Electron, Proton.
The next topics in Atomic Structure & Periodicity are Thomson's Plum Pudding Model and Rutherford's Gold Foil Experiment.
Yes. The interactive lesson includes a self-check question on Neutron, and the Atomic Structure & Periodicity quiz draws on every topic in this area.
Neutron is topic 15 of 115 in Atomic Structure & Periodicity.