150 likes | 749 Views
Molecular Orbitals. An overview. MO Theory. Robert Mullikan won the Nobel Prize in 1966 for developing this theory. This theory describes the electrons in orbitals belonging to the entire molecule. Molecular Orbitals. A molecular orbital (MO) can hold a maximum of two electrons.
E N D
Molecular Orbitals An overview
MO Theory • Robert Mullikan won the Nobel Prize in 1966 for developing this theory. • This theory describes the electrons in orbitals belonging to the entire molecule.
Molecular Orbitals • A molecular orbital (MO) can hold a maximum of two electrons. • A MO has a definite energy. • We can represent an MO with an electron-density cloud.
LCAO • Linear Combination of Atomic Orbitals • Whenever two atomic orbitals overlap, two molecular orbitals form. • # in = # out • Energy is conserved, so… • One orbital will be lower in energy • One orbital will be higher in energy
The Two Orbitals • s* Antibonding orbital • Very little electron density between the nuclei • Higher in energy • Destabilizes bond formation • s Bonding orbital • Promotes bond formation • Electron density is between the nuclei • Lower in energy
Bond Order • In MO theory, bond stability of a covalent bond is related to its bond order. • Bond order = ½(# bonding electrons - # antibonding electrons) • Bond order can be an integer or a fraction
Compare bond orders • Which would be more stable: He2 or He2+? Justify your answer.