[samiam]

So when you start fill d sub levels the energy drops and so the the p sub level becomes higher in energy i.e [Ar]4s^2 3d^2 would actually be [Ar] 3d^2 4s^2 because d sub level lost energy right.


so say a question is find Electronic config of Ga^2+

Ga Electronic config is [Ar]3d^10 4 s^2 5p^1 so now it would be [Ar]3d^10 5s^1 ?

[samiam]

So when you start fill d sub levels the energy drops and so the the p sub level becomes higher in energy i.e [Ar]4s^2 3d^2 would actually be [Ar] 3d^2 4s^2 because d sub level lost energy right. this happens for all d sub levels right? and not just the 3d sub levels?


so say a question is find Electronic config of Ga^2+

Ga Electronic config is [Ar]3d^10 4 s^2 5p^1 so now it would be [Ar]3d^10 5s^1 ?

[stewie griffin]

Assuming you've got the correct configuration for Ga to start (I don't have a periodic table on me at the moment and am too lazy to google it) then I would say the correct answer should be [Ar]3d¹⁰4s². You take the electrons from the highest energy orbitals. The way the configurations are written, the energy increases as we write more shells and subshells. So take away the 5s¹ first and then take one away from the 4s².