SCC Education

Molecular Orbital Theory

Molecular Orbital Theory
In the molecular orbital model, orbitals on individual atoms interact to produce new orbitals, called molecular orbitals, which are now identified with the whole molecule.

THROW OUT THE IDEA OF LOCALIZED BONDING
Why Do Atoms Form Molecules
The Aufbau principle tells us to put electrons into the lowest energy configuration in atoms.  Similarly, molecules form when the total energy of the electrons is lower in the molecule than in individual atoms.
Just as we did with quantum theory for electron in atoms, we will use the molecular quantum theory to obtain.
1. Molecular Orbitals  What are the shapes of the waves?
Where are the lobes and nodes?
What is the electron density distribution?
2. Allowed Energies.  How do the allowed energies change when bonds form?

Wave-functions and Energies: Bonding in H2
If we calculate the wave functions and allowed energies of a two proton, two electron system as a function of separation between the nuclei (the bond length), then we see how two atoms are transformed into a molecule.
This calculation tells us
Whether a bond forms - Is the energy of the molecule lower than the two atoms?
The equilibrium bond length - What distance between the nuclei corresponds to the minimum in the energy?
The structure of the bond - What is the electron density (charge) distribution (y2)?
Electronic properties of the molecules
Diatomic Molecular Orbital Theory
In the case of diatomic molecules, the interactions are easy to
see and may be thought of as arising from the constructive
interference of the electron waves (orbitals) on two different
atoms, producing a bonding molecular orbital, and the
destructive interference of the electron waves, producing an
antibonding molecular orbital

This Approach is called LCAO-MO
(Linear Combination of Atomic Orbitals to Produce
Molecular Orbitals)

sharma sir,scceducation,scc,ssc,free cbse notes,free study material,maths,mathematics,science,9718041826,  Molecular Orbital Theory,  Molecular Orbital Theory,  Molecular Orbital Theory,  Molecular Orbital Theory,  Molecular Orbital Theory 