2
$\begingroup$

My lecturer says that molecular orbitals don't change when electrons are added or removed from a molecule, but I don't understand why. As electrons are described by wave functions, surely more or fewer electrons means that the electrons interact differently and consequently the atomic orbital wave functions interact i.e. interfere differently to form different MOs.

$\endgroup$
  • 10
    $\begingroup$ They do change. $\endgroup$ – orthocresol Dec 7 '19 at 18:36
  • 2
    $\begingroup$ You are correct. While sometimes, for the sake of a simpler calculation, we might assume the orbitals remain the same with the addition/removal of an electron, they should always relax somewhat due to the new electronic configuration. $\endgroup$ – Tyberius Dec 7 '19 at 18:41
  • 1
    $\begingroup$ This ties into the difference of the concepts of vertical and adiabatic ionization. $\endgroup$ – Nicolau Saker Neto Dec 7 '19 at 21:20
0
$\begingroup$

The molecular orbitals do change when electrons are removed or added. But what does not change is the relative order of these orbitals with respect to other orbitals. If a given orbital has a higher energy than another one, it will remain so if you add one electron or it you remove one electron, whatever the absolute values of these energies.

$\endgroup$
  • 7
    $\begingroup$ "The molecular orbitals do change when electrons are removed or added. But what does not change is the relative order of these orbitals with respect to other orbitals" Proof or citation of proof, please - at the very least please explain how you are labelling the orbitals in varying geometries. $\endgroup$ – Ian Bush Dec 7 '19 at 21:54
  • 1
    $\begingroup$ When the energy relative order of atomic orbitals changes by the electron filling,( like 4s vs 3d ), why it should not for molecular orbitals ? $\endgroup$ – Poutnik Dec 8 '19 at 9:38

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.