Summary of Molecular Orbitals and Their Applications

What is a molecular orbital (MO)?

A region of space where electrons in a molecule are most likely to be found, formed by the combination of atomic orbitals from bonded atoms.

What are the two types of molecular orbitals and their functions?

Bonding Orbitals: Stabilize the molecule by increasing electron density between nuclei. Antibonding Orbitals: Destabilize the molecule by creating a node between nuclei.

What is the bond order formula?

Bond Order = (nbonding - nantibonding) / 2

What does a bond order greater than 0 indicate?

The molecule is stable.

How do you determine the stability of a molecule using bond order?

A bond order of 0 indicates instability and that the molecule does not exist under normal conditions.

What is the significance of partially filled or low-energy molecular orbitals in reactivity?

They often make the molecule more reactive.

What is the order of molecular orbitals for Li2 through N2?

σ2s < σ2s* < π2p < σ2p < π2p* < σ2p*

What characterizes diamagnetic species?

All electrons are paired; weakly repelled by a magnetic field.

What characterizes paramagnetic species?

Contains unpaired electrons; attracted to a magnetic field.

What is the significance of the HOMO-LUMO gap in chemical reactivity?

A smaller gap indicates higher reactivity, while a larger gap indicates lower reactivity.

What is the role of the HOMO in molecular reactions?

It contains the highest-energy electrons and determines how the molecule donates electrons.

What does LUMO stand for, and what is its role?

Lowest Unoccupied Molecular Orbital; it is the lowest-energy orbital available to accept electrons.