Molecular Orbitals Theory

These flashcards cover essential vocabulary and concepts related to Molecular Orbitals Theory and its comparison with Valence Bond Theory.

Molecular Orbitals (MO)

Regions in a molecule where electrons are likely to be found, formed by the linear combination of atomic orbitals (LCAO).

Bonding MO

A molecular orbital formed when atomic orbitals combine constructively (AO1 + AO2), resulting in higher probability of finding electrons between nuclei.

Anti-bonding MO

A molecular orbital formed when atomic orbitals combine destructively (AO1 - AO2), resulting in lower probability of finding electrons between nuclei.

Bond Order

A measure of the stability of a bond calculated as the difference between the number of electrons in bonding and anti-bonding MOs, divided by two.

Aufbau Principle

The principle stating that electrons occupy the lowest energy orbitals first.

Pauli Exclusion Principle

The principle stating that no two electrons can have the same set of quantum numbers, thus limiting the number of electrons in each orbital.

Hund’s Rule

The rule stating that electrons will fill degenerate orbitals singly before pairing up.

VB Theory

Valence bond theory where bonds are localized between pairs of atoms and result from the overlap of atomic orbitals.

MO Theory

Molecular orbital theory where bonding electrons are delocalized throughout the entire molecule.

Hybrid Atomic Orbitals (HAOs)

Atomic orbitals that have been mixed to form new orbitals suitable for the pairing of electrons in chemical bonds.

Resonance

The concept where a molecule can be represented by two or more valid Lewis structures, indicating delocalization of electrons.

LCAO (Linear Combination of Atomic Orbitals)

A method used to construct molecular orbitals by combining atomic orbitals.

Stable Molecule

A molecule with a bond order greater than 0, indicating it is more stable than the separate atoms.

Diatomic Molecule

A molecule composed of two atoms, which can be homonuclear or heteronuclear.

Heteronuclear Diatomic Molecule

A diatomic molecule that contains two different elements, leading to different energy levels for atomic orbitals.

Valence Electrons

The electrons in the outermost shell of an atom, which are involved in bonding.

Electronegativity

A measure of the tendency of an atom to attract a bonding pair of electrons.