Sodium has two 1s electrons, two 2 s electrons, six 2p
electrons and one 3s electron.
     

3p

 

3s

           
     

2p

 

2s

           
               

1s

           

Let's summarize this electron distribution for sodium as

1s22s22p63s1

The superscripts tell us how many electrons there are of each type.


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