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Pauli's Exclusion Principle.

  1. Jun 30, 2015 #1
    I was reading about the Pauli Exclusion Principle and I had a doubt. This principle tells us that a maximum of two electrons can be present in an energy level and the spin of the electrons has to be in the opposite direction.

    But S orbital can hold a maximum of two electrons. This is fine but what about the next orbital called P orbital. It can hold upto 8 electrons?

    On further study I found that in the first orbital there can be two electrons with opposite spins. But (Note here) in the next p orbital it has subshells namely 2s, 2px, 2py and 2pz. Each subshell contains maximum 2 electrons.

    Is this line of thought correct Drakkith?
    Last edited: Jun 30, 2015
  2. jcsd
  3. Jun 30, 2015 #2
    Also tell me how the orbitals K,L,M are related to orbitals s,p,d,f? Whats the difference?
  4. Jun 30, 2015 #3


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    Staff: Mentor

    That's the Pauli exclusion principle, not the Heisenberg uncertainty principle.
  5. Jun 30, 2015 #4
    I think I have the answer to that Drakkith.

    k l m and n are shells while s p d and f are subshells.
  6. Jun 30, 2015 #5
    Sorry for that mistake. Yes I am talking about the pauli exclusion principle.
  7. Jun 30, 2015 #6
    I think if I am to be corrected. The L orbital can hold upto 8 electrons. That also would mean L orbital has subshells namely 2s, 2px, 2py and 2pz. Is this correct?
  8. Jul 1, 2015 #7
    To designate a particular subshell we write the number of the shell itself followed by the subshell designator.

    1 s the first shell has one orbital type associated with it.
    2 s p the second shell has two orbital types associated with it.
    3 s p d etc
    4 s p d f
    5 s p d f g
  9. Jul 1, 2015 #8
    Correct me if I am wrong. The next energy level M has 9 subshells. 3s has one subshell. Then 3p has 3 subshells namely 3px 3py 3pz. Then the 3d has five subshells namely 3dxy 3dxz 3dyz 3dx2-y2 and 3dz2. So it can hold upto 18 electrons. Am I right?
  10. Jul 1, 2015 #9
    A table would help to explain further. This table shows quantum number m along with quantum number l and n. It is clear from this table that m (Quantum number) has different values and those values determine the number of shells.

    n l m
    3 0 0 3s

    3 1 -1 3p
    3 1 0
    3 1 1

    3 2 -2 3d
    3 2 -1
    3 2 0
    3 2 1
    3 2 2
  11. Jul 1, 2015 #10


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    Science Advisor

    Shells and subshells are not orbitals. And s and p orbitals are only degenerate (i.e. have the same energy) in hydrogen like atoms.
    The Pauli principle also doesn't say that there can only be two electrons in an energy level but only two electrons in an orbital. But there may be several orbitals having the same energy.
  12. Jul 1, 2015 #11
    It would be useful to distinguish between orbitals, shells and subshells. The quantum numbers determine this, So if

    • They have the same n it is called shell
    • They have same n and l it is called sub-shell
    • They have the same n, l, and ml it is called orbital
  13. Aug 27, 2016 #12
    Think of it this way: Pauli Exclusion Principle says that no two electrons can have the same set of the 4 quantum states which distinguish the electrons around an atom: N, L, M, or S. If they have the same N,L, or M, they can only be distinguished by their S (spin).
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