Why does 4s fill up before 3d?

[MariaJohn1D]

Why does the 4s orbital fill up before 3d orbital other than that it's at a "lower energy level"?

[Vivian Gonzalez 1A]

The only reason I can think of is since the 3d state is higher in energy than the 4s state, the 4s state would fill up faster because it would take less energy.

[KateCaldwell 1A]

The only reason I can think of is since the 3d state is higher in energy than the 4s state, the 4s state would fill up faster because it would take less energy.

I would have to agree with Vivian as the 4s electrons are lost first during ionization. The electrons lost first, have the highest energy level which is al the electrons furthest from the nucleus. Since they are the furthest from the nucleus, they are also the easiest to fill up.

[salvadoralvizo1J]

Is there any particular reason as to why orbitals are named the way they are, or where these letters chosen at random?

[Lily Emerson 1I]

s, p, d, and f are short for sharp, principle, diffuse, and fundamental based on the type of spectral lines the orbitals make