Valence Bond Theory + Molecular Orbitals

Valence Bond Theory

a merger of Quantum Mechanics and Lewis's Model for shared electron pairs

Sigma Bond

bond where electron density is the highest between 2 atoms along "bond axis"

Hybridization

atomic orbitals can be mixed to generate new, hybrid atomic orbitals in different geometries

Pi Bond

bond where the electron density is highest above and below the "bond axis"

Chirality

not superimposable with its mirror image

Isomers

same chemical formulas but different structural formulas

Aromaticity

a property of cyclic molecular structures with pi bonds in resonance that gives increased stability. (Benzene, alternating single + double bonds)

Molecular Orbitals

these form when atomic orbitals combine. If 2 atomic orbitals combine, 2 molecular orbitals result.

Bonding Orbitals

Lower energy than the atomic orbitals that made it. Increased electron density between nuclei. Help hold atoms together.

Anti-Bonding Orbitals

Higher energy than the atomic orbitals that made it. Decreased electron density between nuclei (nodes), destabilize molecules.

Bond Order Calculation

1/2(bonding electrons - anti bonding electrons)

Diamagnetic

no unpaired electrons, doesn't interact with a magnetic field (nitrogen)

Paramagnetic

has unpaired electrons, does interact with a magnetic field (oxygen)

HOMO

highest occupied energy level

LUMO

lowest unoccupied energy level

HOMO-LUMO GAP

energy required to excite an electron from HOMO to LUMO. Basis of solar energy.