Mass of Neutron

Sep 06, 2022, 16:45 IST

Relative masses of protons, neutrons and electrons

Sub atomic particles are extremely small and almost mass less. Still if we compare the mass of protons, neutron and electron it is observed that mass of Neutrons and Protons are almost equal whereas mass of electron are very less as compared to mass of proton and Neutrons. Therefore when we calculate amu the mass of electron is negated.  

Relative Mass of Proton Neutron and electron are

In this relative mass calculation we have assume that a neutron has a mass of 1, then the relative masses of proton and electron are.

Neutron = 1

Proton = 0.99862349

Electron = 0.00054386734

Mass of Neutrons In Kg

Neutron = 1.6749286*10-27 kg

Proton = 1.6726231*10-27kg

Electron = 9.1093897*10-31 kg

Mass of Neutron in MeV

Neutron = 939.56563 MeV

Proton = 938.27231 MeV

Electron = 0.51099906 MeV

Fundamental Properties of Proton neutron and Electron 

1. Electron:  Electron is a universal constituent of matter. 

  • Discovery:  It was discovered by J.J. Thomson in 1886, through the study of cathode rays (Julius Plucker) and the name electron was proposed by Stoney.
  • Charge: It was determined by Millikan by oil drop experiment as -1.602x10-19 coulombs or 4.803x10-10 e.s.u.
  • Mass: It was found by J.J.Thomson as 9.11x10-28 g. (nearly equal to 1/1837th of mass of hydrogen atom).
  • Specific charge:  e/m ratio is called specific charge and was determined by Thomson as 1.76x108 coulombs/gm.
  • Mass in amu:  It is 0.0005486 amu.
  • Mass of one mole of electrons: It is 0.55 mg.
  • Charge on one mole of electron is approx. 96500 coulombs or 1 faraday.
  • Density: 2.17x1017 g/cc. 
  • Radius: It is of the order of 10-15 cm.
  • Symbol: -1e0.
  • Location: Outside the nucleus.

2. Prot​on:

  • Discovery: It was discovered by Goldstein through perforated cathode rays experiment which showed the presence of anode or canal rays.
  • Charge: It carries unit positive charge i.e. 1.602 x 10-19 coulombs or 4.803x10-10 esu.
  • Mass: It was found to be 1.672x10-24 g or 1.672 x 10-27 kg.  This mass is 1837 times heavier than an electron.
  • Specific charge (e/m): It is 9.58 x 104 coulomb/gm (The value of e/m was maximum four hydrogen gas when taken inside the discharge tube. 
  • Mass of 1 mole of proton is nearly 1.007 mg.
  • Charge on 1 mole of proton is 96500 coulombs or 1 faraday
  • The volume of a proton is approximately 1.5x10-38 cm3.
  • Symbol: +1p0 or 1H1
  • Location:  lies inside the nucleus.

3. Neut​ron:

  • Discovery: It was discovered by Chadwick in 1932 by bombarding Be atom with high speed alpha-particles.
  • Charge: Charge less or neutral particle.
  • Mass: Its mass is 1.675x10-24 g or 1.675x10-27 kg.
  • Density: Its density is 1.5x1014 g/cm3 and is heavier than proton by 0.18%.
  • Specific charge: It is zero.
  • Mass of 1 mole of neutron is nearly 1.0087 g.
  • Disintegration: Isolated neutron is unstable and disintegrates into electron, proton and neutrino.
  • Among all the elementary particles neutron is the heaviest and least stable.
  • Symbol: 0n1
  • Location: Lies inside the nucleus.

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