[diccup]

How differentiates bonding and antibonding in MO diagram?
Please let me know if anyone know good website or book for that.
I prefer website though.
Thanks,

 

[lucas89]

I tried looking up websites on my inorganic chemistrys web page, but there weren't any, and google hasn't helped much either. All I can say is for a general rule: the lower orbitals are bonding, the higher ones are anti. This is because the y-axis is labeled with energy, which increases the higher you go up. Bonding orbitals are of lower energy, and antibonding orbitals are of higher energy.

Of course, you have to keep in mind that the s-orbitals will have bonding and anti-bonding, as will the p orbitals (and p also has non-bonding degenerate orbitals). The s-orbitals are of lower energy, so they appear lower on the MO than the p's. I guess generally, the order could go like this:

p-antibonding
p-nonbonding
p-bonding

s-antibonding
s-bonding

Unfortunately, the concept of s-p orbital mixing may (and usually does) mix that order up by lowering the bonding energies, and increases the energy of the antibonding. Maybe your textbook can explain this concept a bit more than I can. Most general first year chemistry books kind of skim the surface of the topic, but maybe that's all the information you'll need to get the idea of s-p mixing.

I hope this helped.