3d Orbital [ENDORSED]

[Sabah Islam 1G]

I understand that the 4s orbital is filled up before the 3d orbital, but why is the 4s orbital filled up before the 3d orbital?

[sahiltelang-Discussion 1J]

Atoms always want to be in the lowest energy state possible. Thus it requires less energy for an atom to have electrons in a 4s orbital rather than a 3d orbital. This can get confusing bc 4 is considered a higher energy level.

[Jessica Benitez 1K]

When we look at the order of elements in the periodic table, we notice that the first two elements in the fourth row are part of the s-block. Therefore, 4s has a lower energy than 3d. However, for multi electron atoms after atomic number 20, 4s has a higher energy than 3d.