Atomic orbitals to molecular orbitals

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Atomic orbitals to molecular orbitals[edit]

We start with the simple principle that atomic orbitals can be combined to give molecular orbitals. In building up our combinations, the overlap between atomic orbitals is determined by their energy, orientation and size.

In the simple example of the hydrogen molecule, the two 1s atomic orbitals (one on each H atom) are combined to give two molecular orbitals:

Ao mo.gif

In this case, the energy, orientation and size of the 1s atomic orbitals on each H atom are the same. In the ground state of the hydrogen molecule, the two electrons present occupy the bonding MO, and so hydrogen is a nice stable molecule!

In the next section, we extend this picture to some triatomic molecules.