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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: Lewis on December 18, 2019, 12:47:47 PM

Title: Atomic orbitals confusion
Post by: Lewis on December 18, 2019, 12:47:47 PM

Hi.

I'm confused about filling 3d and 4s subshells. When writing electrons configuration for transition metal (for example), why do we fill 4s before 3d, yet when this same metal atom gets ionized, 4s electrons are removed first (assuming that 4p isn't filled)?

Also, why do subshells become more stable when they are half-filled or fully-filled with electrons?

What I think:
- 4s is higher than 3d, but 3d extends more away from the nucleus than 4s does.
- Half filled: because they don't face repulsion force from another electron in the same orbital maybe?

Title: Re: Atomic orbitals confusion
Post by: Corribus on December 18, 2019, 02:50:34 PM

You can't treat the orbital energies as though they are static things. When you remove an electron from a shell, it affects the energies of all the other orbitals. The situation also changes when the core nuclear charge changes. As to why the orbital energies fill up in an unexpected order, here is a useful reference:

https://www.chemguide.co.uk/atoms/properties/3d4sproblem.html

Title: Re: Atomic orbitals confusion
Post by: Lewis on December 21, 2019, 11:38:39 AM

Quote from: Corribus on December 18, 2019, 02:50:34 PM

You can't treat the orbital energies as though they are static things. When you remove an electron from a shell, it affects the energies of all the other orbitals. The situation also changes when the core nuclear charge changes. As to why the orbital energies fill up in an unexpected order, here is a useful reference:

https://www.chemguide.co.uk/atoms/properties/3d4sproblem.html

Sorry for the late reply, and thanks, that explains a lot.