Molecular Orbital Theory

Σ orbital

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

The ________ is σ2pz <𝜋₂ₚₓ and 𝜋₂ₚ if Z= or> 8.

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