Electronic configuration in the valence shell of Barium is

The electronic configuration in the valence shell of silicon is The rule violated is

The electronic configuration in the valence shell of silicon is . The rule violated is

The electronic configuration of valence shell of Cu is 3d^(10)4s^(2) . How is this configuration explained ?

Name the elements of the 13th group and give general electronic configuration of their valence shells.

Which of the following can be a stable ground state electronic configuration (only valence shell) of carbon atom? : , , ,

The electronic configuration of Halogens in their valence shell is