Neutron: Definition, Discovery and Properties
Definition of Neutron
A neutron is a fundamental subatomic particle present in the nucleus of an atom. It has no electric charge and is represented by the symbol ${}_{0}^{1}n$
Discovery of Neutron
The neutron was discovered by James Chadwick in 1932.
Discovery Experiment
Chadwick bombarded a beryllium (Be) target with α-particles emitted from polonium. Highly penetrating neutral radiations were produced. These radiations struck a paraffin wax block and ejected high-speed protons. From the conservation of energy and momentum, Chadwick concluded that the radiations consisted of neutral particles having a mass nearly equal to that of a proton. He named these particles neutrons.
Nuclear Reaction:
${}_{2}^{4}He+{}_{4}^{9}Be\rightarrow{}_{6}^{12}C+{}_{0}^{1}n$
Properties of Neutron
1. A neutron has no electric charge.
2. Its mass is 1.6748 × 10⁻²⁷ kg or 1.008665 u.
3. Being neutral, it is neither attracted nor repelled by atomic nuclei and can penetrate deeply into matter.
4. It has low ionising power.
5. A neutron inside the nucleus is stable.
6. A free neutron is unstable and decays into a proton, an electron, and an antineutrino.
${}_{0}^{1}\mathrm{n}\rightarrow{}_{1}^{1}\mathrm{H}+{}_{-1}^{0}\mathrm{e}+\bar{\nu}$
7. The mean life of a free neutron is about 1000 s (16.6 minutes).
8. Thermal neutrons have a speed of about 2200 m s⁻¹ and an energy of about 0.025 eV.
9. The spin of a neutron is
$S = \frac{1}{2}\left(\frac{h}{2\pi}\right)$
10. The magnetic moment of a neutron is −1.91 nuclear magnetons.
Conclusion
The neutron is a neutral constituent of the atomic nucleus. Its discovery by James Chadwick in 1932 completed the basic picture of atomic structure and played a crucial role in the development of nuclear physics.
Frequently Asked Questions (FAQs)
What is a neutron?
A neutron is an electrically neutral subatomic particle present in the nucleus of an atom. It has a mass slightly greater than that of a proton.
Who discovered the neutron?
The neutron was discovered by James Chadwick in 1932 through experiments involving the bombardment of beryllium with alpha particles.
Why was the discovery of the neutron important?
The discovery of the neutron explained the existence of isotopes and helped scientists better understand atomic structure.
What is the charge of a neutron?
A neutron has no electric charge, making it a neutral particle.
What is the mass of a neutron?
The mass of a neutron is approximately 1.675 × 10⁻²⁷ kg or 1.008665 atomic mass units (u).
Where are neutrons found?
Neutrons are found in the nucleus of atoms along with protons, except in the nucleus of ordinary hydrogen, which contains only one proton.
What are the main properties of neutrons?
Neutrons are electrically neutral, have a mass slightly greater than protons, reside in the atomic nucleus, and contribute to nuclear stability.
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