[John489]

I just have a simple question pertaining the bonding and anti bonding molecular orbitals.

I realize the concept of anti bonding and bonding between orbitals, however, what would be the proof of Bonding being stabilizing and Anti-Bonding being non stabilizing. Is it related to the probabilities of electron density?

Thanks in advance

[fledarmus]

I'm not sure exactly what you are asking, but it sounds like you are trying to put the cart before the horse. The molecular orbital which is stabilizing is called the "bonding" orbital, precisely because it is stabilizing - having electrons in the bonding orbital rather than in the separate atomic orbitals is more stable, or there wouldn't be a bond between the two. The molecular orbital which is destabilizing is called the "anti-bonding" orbital precisely because it is de-stabilizing - putting electrons into that orbital reduces that strength of the bond, until it becomes more stable for the atoms to be separate and the bond no longer exists.

So the proof of Bonding being stabilizing, is simply that the stabilizing MO is called the bonding orbital.

Now if you are actually looking for proof that the particular version of the mathematical construct we use to combine two atomic orbitals to form two molecular orbitals, one of which is stabilized and one de-stabilized relative to the two atomic orbitals, that becomes a different question.

[John489]

I realize my question is ambiguous,so let me reframe it.

Are wave functions added in case of bonding and if so it will increase the probability of electron being in that particular area. But wht confuses me is the relation with this increased probability to the stabilizing effect it will have to the bond.

Does that help?

Another version- why does having density in between the two nuclei stabilizing?

[fledarmus]

I think the best that I could do without math would be a very simple example. Think of a hydrogen atom vs a hydrogen molecule, and the difference in attractive force between a single proton and an electron cloud with a -1 charge in the atom, and the attractive force between each +1 charged hydrogen nucleus and the -2 charged electron cloud of a bonding molecular orbital between them.

[John489]

So basically making a 2 e- cloud closer to a hydrogen nucleus containing a proton (1+) is stabilizing in case of bonding and vice versa?

More negative charge surrounding the positive charge is stabilizing? 

[Jorriss]

I realize my question is ambiguous,so let me reframe it.

Are wave functions added in case of bonding and if so it will increase the probability of electron being in that particular area. But wht confuses me is the relation with this increased probability to the stabilizing effect it will have to the bond.

Does that help?

Another version- why does having density in between the two nuclei stabilizing?

Physically, it makes sense that having electron density in between two positive centers will increase the stability.

But mathematically, what one sees in general chemistry or even physical, is found by taking a linear combination of atomic orbitals. Adding two wave functions does not necessarily mean bonding and subtracting does not have to mean antibonding, it just works that way in hydrogen (and I imagine any simple diatomic).

http://en.wikipedia.org/wiki/Linear_combination_of_atomic_orbitals

Read away and let us know if you have questions.

[juanrga]

I just have a simple question pertaining the bonding and anti bonding molecular orbitals.

I realize the concept of anti bonding and bonding between orbitals, however, what would be the proof of Bonding being stabilizing and Anti-Bonding being non stabilizing. Is it related to the probabilities of electron density?

Thanks in advance

Stability is given by :delta:E < 0, where E is energy.

Bonding molecular orbitals have less energy that atomic orbitals. Therefore the molecule is more stable than atoms alone and the bonding is made.

Anti bonding molecular orbitals have more energy than atomic orbitals. Therefore the atoms alone are more stable and no bonding is made.