Electron Configuration

[sarahtang4B]

when do we know if an electron fills the d shell and not the s shell first. like why do we skip 4s2 sometime and jump to 3d10 shell?

[804991762_4A]

It's not that we skip 4s2, but rather its because we have to put in order of lowest energy to highest and 4s2 has a higher energy than 3d, therefore it will be []3d4s

[danicatran4]

But in what instance would 3d (or any d orbital) have a lower energy than s? Is it all the time?

[Mariah Hill]

Why does 3d have a lower energy the 4s?

[nataliefgarcia3I]

Can someone please explain this because I am also confused.

[Jewelyana3A]

I was also confused about the correct order and way to write the electron configuration. I would definitely ask a TA for clarification, but I think that there are just two ways to write it. For example, for Cobalt you can write [Ar]3d^74s^2 or [Ar]3d^9. Again I'm not complete certain, but it may be just two ways of writing it.