Electron Configuration for transition metals

[Katie 3H]

For All d-orbital, or transition metals?, do the electrons in the s level atomically try to fill the d level before it? No matter what?

[Hannah_Pon_1F]

So it's a little complicated but from my understanding (talking specifically about 4s and 3d, but can be generalized)

- The elements up to argon: There follow the general building up pattern
- Potassium and calcium: The pattern is still working here. The 4s orbital has a lower energy than the 3d, and so fills next.
- The d-block elements: Once you get to scandium, the energy of the 3d orbitals becomes slightly less than that of the 4s, and that remains true across the rest of the transition series, so the d orbitals are being filled. The 4s behaves as the outermost orbital/energy level.

For the two exceptions Cr and Cu and their respective groups, it is more stable to fill the d orbitals than keep 4s2, thus:
Cr: [Ar]3d54s1
Cu: [Ar] 3d104s1

For more detail: https://chem.libretexts.org/Bookshelves ... _Chemistry)/Electronic_Structure_of_Atoms_and_Molecules/Electronic_Configurations/The_Order_of_Filling_3d_and_4s_Orbitals

[Reece Fong 2k]

The s subshell will fill before the d subshell UNLESS a d5 or d10 configuration can be reached first. For example, for Cr, instead of [Ar]4s23d4, itll be [Ar]3d54s1, where the d subshell comes first due to it being less energy.

[Michelle_Duong_3H]

Hello,

The s orbital is filled before any d orbitals for the first two groups of the periodic table because its energy is lower. However, once there are three or more valence electrons, the d subshell is lower in energy. While the s orbital is still filled first (with the exception of when a half-full or full d subshell can be achieved), the d subshell will be listed before the s subshell in the electron configuration.

Hope this helps!

[Jordan Kaplan 2E]

For elements past 3p6, 4s will get filled first because that orbital has a lower energy. However, once electrons fill 4s and move onto the 3d orbital, the 3d orbital now has a lower energy level which is why it gets written before the 4s in electron configurations

[Justin_Choo_3J]

Hello!!

d-Orbitals are written first in electron configuration because they have more energy than 4s which means that the 4s orbital which will fill first, followed by all the 3d orbitals.