Chapter 6: Chemical Bonding II: Valence Bond Theory and Molecular Orbital Theory

valence bond theory

An advanced model of chemical bonding in which electrons reside in quantum-mechanical orbitals localized on individual atoms that are a hybridized blend of standard atomic orbitals; chemical bonds result from an overlap of these orbitals.

atomic orbitals

(AOs) A mathematical function that represents a state of an electron in an atom.

hybridization

A mathematical procedure in which standard atomic orbitals are combined to form new, hybrid orbitals.

hyrid orbitald

Orbitals that form from the combination of standard atomic orbitals and that correspond more closely to the actual distribution of electrons in a chemically bonded atom.

pi bond

The bond that forms between two p orbitals that overlap side to side.

sigma bond

The bond that forms between a combination of any two s, p, or hybridized orbitals that overlap end to end.

isomers

One of two or more molecules with the same chemical formula but with a different structure.

molecular orbitals

(MO) A mathematical function that represents a state of an electron in a molecule.

molecular orbital theory

(MO) An advanced model of chemical bonding in which electrons reside in molecular orbitals delocalized over the entire molecule. In the simplest version, the molecular orbitals are simply linear combinations of atomic orbitals.

bonding orbital

A molecular orbital that is lower in energy than any of the atomic orbitals from which it was formed.

antibonding orbital

A molecular orbital that is higher in energy than any of the atomic orbitals from which it was formed.

molecular orbital diagram

(MO) An energy diagram showing the atomic orbitals of the atoms that compose a molecule, the molecular orbitals of the molecule, their relative energies, and the placement of the valence electrons in the molecular orbitals.

bond order

For a molecule, the number of electrons in bonding orbitals minus the number of electrons in nonbonding orbitals divided by two; a positive bond order implies that the molecule is stable.

nonbonding orbitals

An orbital whose electrons remain localized on an atom.