Molecular orbital order

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Miya Eberlein 1J
Posts: 29
Joined: Fri Sep 25, 2015 3:00 am

Molecular orbital order

Postby Miya Eberlein 1J » Sun Nov 08, 2015 8:08 pm

Does anyone know why for Nitrogen and below, the sigma p orbital is located above the two pi orbitals, but it moves to above the pi orbitals for oxygen and above? this was probably mentioned in class but I was just wondering out of curiousity!

Austin Hyun 1F
Posts: 26
Joined: Fri Sep 25, 2015 3:00 am

Re: Molecular orbital order

Postby Austin Hyun 1F » Sun Nov 08, 2015 8:35 pm

Hi Miya,

So this change in the M.O. diagram is because the elements preceding oxygen on the periodic table have a nuclear charge less than 8 (Z<8). In these elements, the sigma orbitals' energies are increased, as they exist along the bond axis, whereas the pi orbitals' energies do not increase, as their electron densities are concentrated away from the bond axis. I hope this clarifies your question! Also, pg. 97 of the course reader may help explain a little more, too, if that helps!

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