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Bonding vs Antibonding

Posted: Mon Nov 02, 2015 4:19 pm
by Camryn Marshall 1C
Im lost on the whole concept of bonding vs antibonding. I understand in terms of molecular orbital theory because I can memorize how the diagram should look but besides that I dont understand it conceptually. For example on number 77 of the homework it says draw the bonding and antibonding orbitals that correspond to the sigma bond in H2. Will someone explain to me how its supposed to look?

Re: Bonding vs Antibonding

Posted: Mon Nov 02, 2015 7:21 pm
by Chem_Mod
Bonding orbitals occur when the two atomic orbitals of the respective atoms overlap while in phase. Antibonding orbitals occur when the two atomic orbitals have overlap while out of phase. Electrons in bonding orbitals stabilize the molecule, while electrons in the antibonding orbitals destabilize the molecule.

Your question about H2 would be a great question to bring to a TA so that she/he can work through it with you. However, if you do the molecular orbital diagram for H2, you will see that there is one bonding sigma orbital, and one antibonding sigma orbital. There are a total of 2 electrons in the molecule (one for each H), so you fill the bonding orbital (fill lowest energy orbitals before moving up to higher orbitals) and then you're done.

Re: Bonding vs Antibonding

Posted: Wed Dec 02, 2015 6:23 pm
by 704628249
If two orbitals are in phase, then they are bonding. These bonding orbitals will stabilize the molecule. If two orbitals are out of phase, then they are anti bonding, and will not stabilize the molecule.