Question

1. Which of the following order of energies of molecular orbitals of N2 is correct?
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Answer 1

Answer:

(i) (π2py ) < (σ2pz) < (π*2px) ≈ (π*2py)

Explanation:

have been taught that the MO diagram is different for molecules with 14 or less electrons than the one used for molecules with 15 or more electrons.

For N2 the orbitals in increasing energy are:

σ1s<σ∗1s<σ2s<σ∗2s<π2px,π2py<σ2pz<π∗2px,π∗2py<σ∗2pz

because it has 14 electrons.

For N2− there are 15 electrons. Will the MO diagram be the same as that of N2 or not? Why?

And because this is a good chance to ask, why is there this difference in orbital energies anyway?