Why do Copper, Silver and Gold break the norm of a full 2 electron s shell in favour of an 18 electron inner shell? Also, why is the next element in group 11 roentgenium likely to have a full s shell?

1 Answer
May 16, 2017

Because a full third inner shell with 18 electrons is more stable than a filled s subshell.


By transferring one of the s electrons to a d orbital the d orbitals become completely filled. Not only is the d orbital filled all of the orbitals in the next lower shell are filled. This creates a great deal of stability.

In contrast a filled s sub shell does not provide the same level of stability. Also the energy level difference between the larger but simpler s orbital and the smaller but much more complex d orbital disappears as the number of protons in the nucleus increases drawing the d orbital electrons closer to the nucleus.