Molecular orbital energy level diagrams shows the filling of electrons in the increasing order of energy. Here, we will discuss the two types of energy levels for filling of electrons in the molecular orbital.
What is energy level diagram for molecular orbital of N2
Here is the electronic configuration for homonuclear diatomic molecules up to N2:
sigma (1s) < sigma*(1s) < sigma (2s) < sigma* (2s) < Pi ( 2px ) = Pi( 2py ) < sigma ( 2pz ) < Pi*( 2px ) = Pi*( 2py ) < sigma*( 2pz )
Here is the electronic configuration for homonuclear diatomic molecules for O2, F2 and Ne2
sigma (1s) < sigma*(1s) < sigma (2s) < sigma* (2s) < sigma ( 2pz ) < Pi ( 2px ) = Pi( 2py ) < Pi*( 2px ) = Pi*( 2py ) < sigma*( 2pz )
Relation between electronic configuration and molecular behaviour
- Stability of molecules in terms of bonding and antibonding electrons
Bonding electrons > Nonbonding electrons, the molecule is stable due to the net force of attraction.
Bonding electrons > Antibonding electrons, the molecule is unstable due to the net force of repulsion.
Bonding electrons = Antibonding electrons, the molecule is unstable. Antibonding electrons have greater influence than bonding electrons.
2. Stability of molecules in terms of bond order
Bond order is half of the difference between the number of electrons present in the bonding and antibonding orbitals.
Bond order = 1/2 ( Nb – Na )
Nb > Na = bond order is +ve
Nb < Na = bond order is -ve.
Nb = Na bond order = 0
For diatomic molecules, the more is bond order, higher has bond energy. For example bond order of 3 has higher bond dissociation energy than bond order 2. Bond order 1,2,3 means 1,2,3 covalent bonds.
3. Bond length in terms of bond order
Bond length is inversely proportional to bond order. Greater the bond order, lesser will be the bond length.
4. Diamagnetic and paramagnetic behaviour
If all the electrons are paired, the molecule is diamagnetic in nature. If the electrons are unpaired, the molecule is paramagnetic in nature. Greater the number of unpaired electrons, more will be the paramagnetic behaviour.
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