What is Neutron

The neutron is a sub-atomic particle and it has a symbol n, which has a neutral charge. It has a slightly greater mass than Proton. Protons and neutrons constitute the nuclei of atoms. Their properties and interactions are described by nuclear physics. The chemical properties of an atom are mostly determined by the configuration of electrons that orbit the atom’s heavy nucleus. Electrons configuration is determined by the charge of its nucleus and that is determined by the number of protons.

neutron nucleus atomic electrons protons

Neutrons do not affect the electron configuration, but the sum of atomic and neutron numbers is the mass of the nucleus.

Atoms of a chemical element that differ only in neutron numbers are called isotopes.

The properties of an atomic nucleus are dependent on both atomic and neutron numbers. With their positive charge, the protons within the nucleus are repelled by the long-range electromagnetic force. Still, a much stronger and short-range, nuclear force binds the nucleons closely together.

Discovery of Neutron

The atoms consist of a small positively charged massive nucleus surrounded by a much larger cloud of negatively charged electrons. In 1920 Rutherford suggested that the nucleus consisted of positive protons and neutrally charged particles, suggested to be a proton and an electron bound in some way.

At a point, electrons were considered to reside within the nucleus because it was known that beta radiation consisted of electrons emitted from the nucleus. Throughout 1920 people assumed the atomic nucleus was composed of protons and nuclear electrons.

But the problem raised that it was difficult to reconcile the proton-electron model for nuclei with the Heisenberg uncertainty relation of quantum mechanics.

Observer properties of atoms and molecules were inconsistent with the nuclear spin expected from the proton-electron hypothesis. This was discovered by Oskar Klein in 1928.

In 1931, Walther Bothe and Herbert Becker found that if alpha particle radiation from polonium fell on beryllium, Boron or Lithium, an unusually penetrating radiation produced. As it was not influenced by any electric field then both the scientist assumed it is Gamma radiation.

Models for an atomic nucleus consisting of protons and neutrons were quickly developed by Werner Heisenberg and others. The proton-neutron model explained the puzzle of nuclear spins.

Beta-decay and Stability of the nucleus

The neutrons and protons bound in a nucleus form a quantum mechanical system wherein each nucleon is bound in a particular, hierarchical quantum state. Protons can decay to neutrons or vice versa within the nucleus. This process is called Beta-decay.

These emitted particles carry away the energy excess as a nucleon falls from one quantum state to a lower energy state while the proton changes to a neutron or vice versa. Such decay processes can occur only if allowed by basic energy conservation and quantum mechanical constraints.

Detection of Neutron by neutron capture

A common method for detecting neutrons involves converting the energy released from neutron capture reactions into electrical signals.

There are other methods too for detecting a neutron but this is easy as neutron capture is not that difficult.


The mass of a neutron cannot be directly determined by mass spectrometry since it has no electric charge. The mass of the proton can be deduced by subtracting proton mass from the deuteron mass.

The neutron is composed of two down quarks and one up quark. The decay of the proton to a neutron occurs similarly through the electroweak force. The decay of one of the proton’s up quarks into a down quark can be achieved by the emission of a W boson.

The geometry of charge distribution

An article published in 2007 featuring a model-independent analysis concluded that the neutron has a negatively charged exterior, a positively charged middle, and a negative core.

In a simplified classical view, the negative “skin” of the neutron assists it to be attracted to the protons with which it interacts in the nucleus.

Neutron stars

At extremely high pressures and temperatures, nucleons and electrons are believed to collapse into bulk neutronic matter called neutronium. This is presumed to happen in neutron stars.

The extreme pressure inside a neutron star may deform the neutrons into a cubic symmetry, allowing tighter packing of neutrons.


The antineutron is the antiparticle of the neutron, it was discovered by Bruce Cork in 1956, a year after the antiproton was discovered. So studying antineutrons provides stringent tests on CPT-symmetry.


I know, I left out a lot of stuff from this topic but it had numerous things to cover which can be found in other blogs as everything in science is entangled with each other and can be covered in other topics.


Leave a Reply

Your email address will not be published. Required fields are marked *