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Bonding and Antibonding MO's (Read 6390 times)
Gerrit-Jan Linker
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Bonding and Antibonding MO's
29.10.09 at 09:09:00
 
Bonding and Antibonding MO's
 
Whether a molecular orbital (MO) is called bonding or anti-bonding depends what happens to the total energy of the molecule when the MO becomes populated. If the energy is lowered the molecule is stabilised and the MO is called bonding. On the other hand if the energy is raised, the molecule is destabilised and the MO is called anti-bonding.
 
In molecules with several atoms a particular MO may be bonding with respect to some adjacent pairs of atoms and antibonding with respect to other pairs. If the bonding interactions outnumber the antibonding interactions, the MO is said to be bonding, while if the antibonding interactions outnumber the bonding interactions, the MO is said to be antibonding.  
 
To find out whether an MO is bonding or anti-bonding in a region of space between two adjecent atoms consider the electron phase, the sign of the wavefunction. When an MO changes sign (from positive to negative) between two atoms, it is said to be antibonding with respect to those atoms. When the sign of the wavefunction does not change the MO is bonding for the atom pair.
 
You can also consider this by inspecting the atomic orbitals (AO's). If the sign of the AO's change the overlap of the AO's is said to be 'out of phase' and as such the electrons present in each antibonding orbital are repulsive and act to destabilise the molecule as a whole. If the sign of the AO's does not change, the overlap of the AO's is 'in phase' and the electrons in each bonding orbital is attractive and acts to stabilise the molecule.
 
Antibonding molecular orbits (MOs) are normally higher in energy than bonding MOs.  
 
Source:
Antibonding - Wikepedia
http://en.wikipedia.org/wiki/Antibonding
P.W. Atkins, Physical Chemistry, 3rd edition
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« Last Edit: 29.10.09 at 10:17:04 by Gerrit-Jan Linker »  

Gerrit-Jan Linker
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Gerrit-Jan Linker
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Re: Bonding and Antibonding MO's
Reply #1 - 30.10.09 at 21:19:26
 
Non bonding
 
Besides bonding and anti-bonding there is also non-bonding as a description of (part of) a MO when the MO does not participate in any bonding.
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« Last Edit: 28.11.09 at 23:28:20 by Gerrit-Jan Linker »  

Gerrit-Jan Linker
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