Physics · nuclei · NEET
James Chadwick discovered the neutron in 1932. He fired alpha-particles (helium nuclei) at a beryllium target. This produced a neutral radiation that could knock protons out of light nuclei like carbon and nitrogen. Using conservation of energy and momentum, he showed this radiation could not be photons and must be a new neutral particle of mass close to the proton. He got the 1935 Nobel Prize for it.
The charge on a neutron is exactly zero. It is electrically neutral. This is the key reason it was found so late: being neutral, it is not deflected by electric or magnetic fields and leaves no track, so it was much harder to detect than the charged proton or electron.
The neutron is very slightly heavier than the proton. Neutron mass = 1.00866 u, proton mass = 1.00727 u. So the order of masses is neutron > proton >> electron. In NEET, remember neutron is the heaviest of these three basic particles.
Because it carries no charge. Detectors of that era worked by sensing the deflection or ionisation trail of charged particles in electric and magnetic fields. A neutral neutron produces no such trail, so it stayed hidden until Chadwick detected it indirectly through the protons it knocked out.
No. A free neutron (outside the nucleus) is unstable. It decays into a proton, an electron and an antineutrino, with a mean life of about 1000 seconds. But inside a nucleus the neutron is stable, which is why nuclei can hold neutrons permanently.
The neutron mass is 1.00866 u, which equals 1.6749 x 10^-27 kg. Since 1 u = 1.66 x 10^-27 kg, multiplying 1.00866 by this gives the value in kilograms. This is one of the standard constants NEET expects you to recall.
A neutron is a neutral (zero charge) subatomic particle found inside the nucleus, along with protons. Its mass is 1.00866 u, slightly more than a proton's mass.
James Chadwick discovered the neutron in 1932 by bombarding beryllium with alpha-particles. He was awarded the 1935 Nobel Prize in Physics for this discovery.
The neutron has zero charge. Its mass is 1.00866 u, equal to 1.6749 x 10^-27 kg.
Because it has no charge, it is not affected by electric or magnetic fields and leaves no ionisation track, so it was detected only indirectly through the protons it knocked out of light nuclei.
A free neutron is unstable and decays into a proton, an electron and an antineutrino with a mean life of about 1000 s. Inside a nucleus, however, the neutron is stable.
