Neutrons

A neutron is a neutral subatomic particle and is present in the nucleus of the atom. They are usually denoted by N and net charge associated with it is zero. It is present in the nucleus and proton and neutron together are called nucleons. Total number of protons and neutrons gives the atomic mass of an element. 

It also stated that neutrons present in the nucleus differ in isotopes as isotopes have the same atomic number but different atomic mass.

For the stability of the atom, the neutron is a must but there is an exception in protium-1.

Nuclear Physics and Properties of Atoms

Nuclear physics is the branch of science in which the study of neutron and other electromagnetic induction is done. Neutrons and protons are together and have the same physical quantity in the nucleons.

Physical properties and chemical properties of an atom is decided by the number of proton and neutron present in the atom - 

• Neutrons are slightly heavier than protons and balance the electron and hold the electron in the atom.

• The number of protons is equal to the number of neutrons in the nucleus or number of a nucleus is greater than one from the number of protons.

• If the number of neutrons gets more than the number of protons in excess in the nucleus then the particle becomes radioactive and breaks up to release alpha or beta rays.

• Neutron has penetrating power greater than gamma rays.

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Discovery of Neutrons

Its existence was noted by the Rutherford Nuclear Model of Atom (Alpha particle scattering experiment. It also gives us remarkable information of the arrangement of the constituent particles) in this experiment where most of the alpha particle passes undeviated, some through smaller angles and some with an angle larger than 180 degrees. It indicated the presence of a particle in the middle part of the atom (nucleus); it marked the presence of a mass particle and the neutron was discovered later in 1932 by James Chadwick.

As electrons have negligible mass and thus the mass of an atom is due to proton only, it would create problems in the model. Thus, it was indicated the presence of the neutral particle with an equal mass of the proton must be present in the atom.

Rutherford realized that atomic mass of different elements cannot be explained unless there is the presence of another particle. Rutherford, in 1920, stated that a kind of neutral particle with a mass equal to the mass of a proton.

In 1932, during the study of the artificial transmutation of atoms, James Chadwick discovered a particle indicated by Rutherford in 1920. When a thin foil of beryllium is bombarded with fast-moving alpha particles and beryllium changes into carbon and emits a neutral particle of the same mass as the proton.

The particle was also found in many other reactions and this new fundamental particle was named neutrons because of its neutral nature.

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Properties of Neutrons

• There are electrically neutral particles. The mass of the neutron is 1.675 x 10−27
  which is slightly greater than the mass of a proton.

• The weight cannot be analytically measured using this technique as they have no electric charge.

• They are highly penetrating but not much when compared to cosmic rays.

• They are unable to ionize a gas. Therefore, they do not produce a track in Wilson's cloud chamber.

• The total sum of the neutrons and protons present in an atom accounts for the approximate mass of an atom in a.m.u (atomic mass unit).

• The neutron is not an elementary particle, as it has a magnetic field.

• These subatomic particles are affected by the magnetic field but have no effect of an electric field.

• Its magnetic field can be related with the quarks substructure and the internal distribution of the charge.

• Its mass can be measured by subtracting the mass of the proton from the atomic mass. 

• A neutron is composed of three quarks and these elementary particles gave neutron its magnetic particle( the Quarks model was discovered in the 1960s).

• The magnetic field of the neutron ( neutral particle) is not zero.

Charge and Mass of Neutrons 

• The charge associated with neutrons is zero. Therefore, neutrons are subatomic particles with a neutral charge. 

• The mass of a neutron is approximately equal to 1.008 atomic mass units. 

• Since neutrons have no charge, their mass cannot be directly determined by mass spectrometry techniques. 

• We can calculate the mass of the neutron by subtracting the mass of the proton from the mass of the deuteron. (The mass of the neutron is negligible, and we can calculate the mass of the neutron by subtracting the mass of the proton from the mass of the deuterium atom).

Application of Neutrons

• Neutrons are highly ionized and penetrating particles and can be used in boron capture therapy and medical uses but they activate the matter when absorbed and leave it to be radioactive.

• It plays an important role in a nuclear reaction (in particular knowledge and behaviour of the neutron has helped in the development of nuclear weapons and nuclear reactors).

• In the development of the neutron lenses.

• Neutrons are used in the method of NAA (neutron activation analysis). They are used to analyze simple samples of materials in a nuclear reactor and neutron emitter is used in finding light nuclei in the environment. 

• It is used in neutron tomography used in medical procedures but it can have unfortunate side effects. It can leave the affected area radioactive thus it is not used widely.

• It is used in boron capture therapy in which a small beam of neutron is used to cure cancer.

• Neutron radiation can deliver energy to cancerous regions in orders of magnitude greater than gamma rays.

• The Uranium-235 and Plutonium-239 are used in the nuclear fission reactors by almost every time by absorption of the nucleus.

• In nuclear scattering facilities where the radiation is used to condense matter in research using X-rays, the warm, hot, and cold neutron application is used.

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Conclusion

This is all about the discovery and definition of neutrons. Understand the difference between this subatomic particle with the rest. Focus on how it is used in different industrial processes these days.