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Electronic configuration of Lanthanoids & Bohr's bury's rule

Electronic configuration of Lanthanoids;

ce (58) to lu(71)  electronic configuration of lanthanoid cannot be predicted corrected by Aufbau principal.

for eg. after filled 6s orbital in barium the next electron in lanthanum should enter 4f orbital in fact it does not happen and next electron goes in 5d orbital. so electronic configuration of lanthanoid[ 57]   |xe|6s^2 5d^1.


Electronic configuration of Actinoids;

electronic configuration of actinoids cannot be predict correctly by aufbau principal

for eg.  After filling 7s orbital in radium(88)  the next electron in actinium should 5f orbital. in fact it does not happen and next electron goes in 6d orbital .so electronic configuration of actinium[89]  |Rn|7s^2 6d^1.
 Bohr's bury's rule (n+l)  rule: 

According to this rule the energy of an orbital depends upon (n+l)  value, the orbital with lower value of (n+l)  will be lower energy  and will filled first.

for eg.  
              3d                     4s
            n=3                   n=4
             l=2                     l=0
        n+l=5                n+l=4

since (n+l)  value is less for 4s  orbital is lower energy is filled earlier than 3d.

if (n+l)  comes out to be same than orbital will lower value of 'n' will be lower energy and is filled first.

for eg.     3d                   4p
              n=3                   n=4
              l=2                    l=1
         n+l = 5               n+l= 5
since ( n+l) value comes out be same for 3d and 4p orbital but value of n is less for 3d orbital  so 3d orbital of lower  energy and is filled earlier than 4p.


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