Molecular Orbital Theory

Σ orbital

________: cylindrically symmetric about the bond axis; no nodal plane along the bond axis.

MO

In ________ theory, valence electrons are delocalized over the entire molecule, not confined to individual atoms or bonds.

relative energy ordering

internuclear region

An electron in an antibonding MO will be excluded from the ________, and thus have a higher energy than if in an atomic orbital.

energy differential

If the ________ is small, then the molecule is not as stable.

𝜋 orbital

________ (bonding orbital): molecular orbital with a nodal plane along the bond axis.

relative energy ordering

The ________ is 𝜋₂ₚₓ and 𝜋₂ₚy <σ2pz if Z <8.

Bond order = ½ ( of bonding electrons

of antibonding electrons)

σ orbital

cylindrically symmetric about the bond axis; no nodal plane along the bond axis

1s

1s = σ₁ₛ* (antibonding MO)

𝜋 orbital (bonding orbital)

molecular orbital with a nodal plane along the bond axis

2pₓ

2pₓ = 𝜋₂ₚₓ*

2pᵧ

2pᵧ = 𝜋₂ₚᵧ*

𝜋 orbital (antibonding orbital)

MO with 2 nodal planes along the bond axis

An electron in a bonding MO will be

attracted to both nuclei, and will be lower in energy (more stable) compared to an atomic orbital for a single nuclei

An electron in an antibonding MO will be

excluded from the internuclear region, and thus have a higher energy than if in an atomic orbital

N molecular orbitals can be created from

N atomic orbitals

Molecular orbitals arise from

adding together (superimposing) atomic orbitals

A linear combination of atomic orbitals (LCAO) creates

molecular orbitals (bonding and antibonding orbitals)

Bond order =

½ (# of bonding electrons - # of antibonding electrons)

The relative energies of the σ2pz compared to the  𝜋₂ₚₓ or y orbitals depend on

the z value of the atoms