4s vs 3d subshells

[Arjun_Anumula_3E]

After the lecture, I still have a question about 4s and 3d subshells. Does the 4s subshell have more energy than the 3d one? Some other online sources were saying otherwise so I'm not quite sure what is true

[Misheel Enkhbold 1C]

Based on the lecture, for Potassium and Calcium, 4s is lower than 3d but once you move to Scandium, 3d state has lower energy than 4s. 4s is lower in energy until it fills up but once it does, it has higher energy than the 3d subshell.

[Chance Lee 1G]

At first the 4s has lower energy, which is why the 4s shell is filled up first. However, once the 4s fills up, the 3d shell would gain an electron. After this, the 3d shell would have less energy than the 4s shell.

[KyleNagasawaDisc3C_Chem 14B2022W_]

Hey Arjun,

The orbitals associated with an atom are filled on a lowest-energy basis. For the sake of clarity, I will be using Calcium as an example.

The two valence electrons purposefully fill the 4s orbital because the 4s orbital is initially lower in energy than the 3d subshell. As the 4s gets filled up, its energy becomes greater than the 3d subshell, resulting in subsequent filling of the 3d subshell. This also rationalizes why the first electrons to be removed to generate a Ca2+ ion are removed from the higher-energy, outermost 4s orbital.

I hope this helps!

[Audrey Banzali-Marks 1A]

Adding onto these posts, when valence electrons are removed from transition metals like Zn, are electrons removed from the 4s subshell or 3d subshell? The 3d subshell isn't full, but would the electrons be removed from 4s since that subshell is the outermost one?