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Pauli’s Exclusion Principle

Hey guys!  How’re all..I hope well. Today I wanna discuss an important topic named Pauli’s Exclusion Principle. 


The electrons in an atom are distributed in a definite way among various shells & subshells.
This distribution is governed by a principle given by Pauli in 1925, known as Pauli’s Exclusion Principle.

It is the quantum mechanical principle which states that two or more identical fermions cannot occupy the same quantum number within a quantum system simultaneously.

In the case of electron in atoms it can be stated as follows :

 It is impossible for two electrons of a poly-electron atom to have the same values of four quantum number like ,

  • Principle quantum number
  • Angular momentum quantum number
  • Magnetic quantum number
  • Spin quantum number
In simply according to the that principal :

“No two electrons in an atom can have all the four quantum numbers same “

In order to illustrate the principle let us consider two electrons present in the K-shell 

n=1(same)   l = 0 (same)  m = 0(same)  s= +1/2 & -1/2(different)

Thus it is quite clear that an orbital can have a maximum of two electrons with opposite spins the orbital with two electrons is called filled orbitals while the orbital having only one electron is known as half filled orbital.
On this basis, we can deduce the number of permitted electrons in various subshells.

e.g. Quantum numbers of 13th, 14th, 15th electron of Chlorine:

It is clear that the quantum number of each electron is different.
I hope you understand today’s discussion. Still any query write to us in comment section. 

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