[awkko808]

In my class we went over MOs very briefly and did examples for O2 O2+ CN CO etc. The teacher also said that you could use MO theory to satisfy the electron configuration of ionic bonds but never went over it. I was wondering if anyone has an example of how this could be done say for NaCl? I have looked on the internet but particularly don't understand how the nonbonding orbitals work and how the orbitals are placed at different energy levels for different atoms.

Also an unrelated question, valence orbitals are the only ones that matter in determing bond order, and thus conceptually are the only ones participating in the bond?
So for N2, whose MO e- configuration is: σ_1s²σ_1s^*2σ_2s²σ_2s^*2Π_2p⁴σ_2p² only the pi and sigma 2p orbitals contribute to the bond?

[juanrga]

In my class we went over MOs very briefly and did examples for O2 O2+ CN CO etc. The teacher also said that you could use MO theory to satisfy the electron configuration of ionic bonds but never went over it. I was wondering if anyone has an example of how this could be done say for NaCl? I have looked on the internet but particularly don't understand how the nonbonding orbitals work and how the orbitals are placed at different energy levels for different atoms.

Also an unrelated question, valence orbitals are the only ones that matter in determing bond order, and thus conceptually are the only ones participating in the bond?
So for N2, whose MO e- configuration is: σ_1s²σ_1s^*2σ_2s²σ_2s^*2Π_2p⁴σ_2p² only the pi and sigma 2p orbitals contribute to the bond?

MO theory is a general model to obtain the wavefunctions of any ordinary molecule/ion or even larger systems as solids (giant molecules), aggregates (water clusters), and so on.

I do not have an electronic example at hand for NaCl, but I have for ICl. I wait can be useful for you



The energy levels for each orbital (atomic or molecular) are obtained by solving the time-independent Schrödinger equation

H Psi = E Psi

Molecular orbitals (M) are obtained by combination of atomic orbitals (A). For instance,

Psi_M = c_A1 Psi_A1 + c_A2 Psi_A2

Think of the special case c_A1 = 0 and c_A2 = 1

Psi_M = Psi_A2

This molecular orbital will have the same energy than the atomic orbital. This orbital is not decreasing the energy of the separated atoms, therefore it is not bonding the atoms. At the same time this orbital is not increasing the energy of the separated atoms, therefore it is not anti-bonding them. It is neither bonding nor anti-bonding. This is the reason which is called a non-bonding orbital.

A typical example are the 2p_x,y,z of Fluorine in HF. There is not 2p orbitals in the H for the combination and the 2p of the F are alone. Think of non-bonding orbitals as a kind of analog of the lone pairs of Lewis theory.

What is the definition of bond order?

[awkko808]

We've only touched up on Schrodinger's equation but now I understand how the orbital energies are calculated - through Schrodinger's equation. May I ask what the c operators stand for? As in c_A1 and c_A2.
As for bond order, I ended up finding the answer to that.

Thank you!

[juanrga]

We've only touched up on Schrodinger's equation but now I understand how the orbital energies are calculated - through Schrodinger's equation. May I ask what the c operators stand for? As in c_A1 and c_A2.
As for bond order, I ended up finding the answer to that.

Thank you!

c_A1 and c_A2 are numerical coefficients that measure the 'importance' or 'weight' of each atomic orbital in the molecular orbital. Their values are obtained when solving the Schrödinger equation.