How many electrons are in the highest energy orbital of the element copper? There is 1 in the outermost shell but what about the highest energy orbital?

Answer 1

the electron configuration for Cu is [Ar]3d¹⁰ 4s¹ so there is one electron in the hightest energy orbital (4s)

Answer 2

That was what I put as my answer but my teacher marked it wrong and said "this is asking for the highest energy orbital versus the outermost shell." But in my book it has 1 as the highest energy orbial:/