MO for heteronuclear diatomic molecules?

How do we know which molecular orbital diagram to draw for heteronuclear diatomic molecules?

Like, for homonuclear diatomic molecules, between lithium and nitrogen, the sigma orbital is higher in energy than the pii orbitals.
And vice versa for atoms between oxygen and fluorine.

However, what about molecules such as BO, CO and NO?

Which molecular orbital diagram do we follow?

Thank you


Posted from TSR Mobile

The more electronegative atom would have more tightly held atomic orbitls hence "lower" in energy reltive to those from less EN atom.

Google "moleculr orbitl of xx" images and check out. sensible textbook on intro to these things usually cover these too.

This isn't the case for NO


Oxygen is more electronegative

And the sigma orbital comes before the pii orbital



Posted from TSR Mobile

How do we know which molecular orbital diagram to draw for heteronuclear diatomic molecules?

Like, for homonuclear diatomic molecules, between lithium and nitrogen, the sigma orbital is higher in energy than the pii orbitals.
And vice versa for atoms between oxygen and fluorine.

However, what about molecules such as BO, CO and NO?

Which molecular orbital diagram do we follow?

Thank you


Posted from TSR Mobile

sigma and pi orbitals change order because of s-p mixing. As you move to the right across the row (Li--->F) the energy gap between s and p orbitals gets larger (because the effective nuclear charge increases). It just so happens that the crossover between the orbitals energies happens between N2 and O2. CO is isoelectronic with N2 , its MO diagram is asymmetrical but has the same mixing affects as N2 (ie the sigma and pi are swapped). NO has smaller s p mixing so its MO diagram looks more like O2 (again it will be lopsided because the atoms have different electronegativities!)