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Q : 1. (1!) (1!) (1!)(1!)( ) 2. (1!) (1!) (1)(1) (1) 3. (1!) (1!) (1)(!)(1) here one (1) is the upper arrow and (!) this is the downward arrow...... among these above mentioned electronic configuration ,which one is correct ? tell me why 2 is correct??
The electronic configuration corresponds to

                           
1S2     2S2        2Px  2Py   2Pz  orbitals.


 Filling of orbitals follow Hunds rule of maximum multiplicity.

Hund's Rule states that:

  1. Every orbital in a sublevel is singly occupied before any orbital is doubly occupied.
  2. All of the electrons in singly occupied orbitals have the same spin

Look at the correct electron configuration of Nitrogen(Z = 7): 1s2 2s2 2p3

Nitrogenexample.jpg

We can clearly see that p orbitals are half filled as there are three electrons and three p orbitals. This is because the three electrons in the 2p subshell will fill all the empty orbitals first before pairing with electrons in them. If we look at the element after Nitrogen in the same period, Oxygen (Z = 8) its electron configuration is: 1s2 2s2 2p4

oxygenexample.jpg

Oxygen has one more electron than Nitrogen and as the orbitals are all half filled the electron must pair up.




 


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