1. The Central Themes of VB Theory
A set of overlapping orbitals has a maximum of two electrons that must have opposite spins.
The greater the orbital overlap, the stronger (more stable) the bond.
The valence atomic orbitals in a molecule are different from those in isolated atoms.
There is a hybridization of atomic orbitals to form molecular
orbitals.

2. Orbital overlap and spin pairing in three diatomic molecules.
Hydrogen, H2
Hydrogen fluoride, HF
Fluorine, F2

3. Hybrid Orbitals Key Points
The number of hybrid orbitals obtained equals the number of atomic orbitals mixed.
The type of hybrid orbitals obtained varies with the types of atomic orbitals mixed.
Types of Hybrid Orbitals sp
sp2
sp3
sp3d
sp3d2

4. The sp hybrid orbitals in gaseous BeCl2.
atomic orbitals
hybrid orbitals
orbital box diagrams

5. The sp hybrid orbitals in gaseous BeCl2.
orbital box diagrams with orbital contours

6. The sp2 hybrid orbitals in BF3.

7. The sp3 hybrid orbitals in CH4.

8. The sp3 hybrid orbitals in NH3.

9. The sp3 hybrid orbitals in H2O.

10. The sp3d hybrid orbitals in PCl5.

11. The sp3d2 hybrid orbitals in SF6.

13. relatively even distribution of electron density over all s bonds
The s bonds in ethane(C2H6).
both C are sp3 hybridized
s-sp3 overlaps to s bonds
sp3-sp3 overlap to form a s bond
relatively even distribution of electron density over all s bonds

14. The s and p bonds in ethylene (C2H4).

15. The s and p bonds in acetylene (C2H2).

16. Contours and energies of the bonding and antibonding molecular orbitals (MOs) in H2.
The bonding MO is lower in energy and the antibonding MO is higher in energy than the AOs that combined to form them.

17. The MO diagram for H2. Energy AO of H AO of H
Filling molecular orbitals with electrons follows the same concept as filling atomic orbitals.
s*1s
Energy
AO of H 1s
AO of H 1s
H2 bond order = 1/2(2-0) = 1
s1s
MO of H2

18. MO diagram for He2+ and He2.
Energy
s*1s
s1s
s*1s
AO of He 1s
AO of He+ 1s
AO of He 1s
AO of He 1s
Energy
s1s
MO of He+
MO of He2
He2 bond order = 0
He2+ bond order = 1/2

19. Bonding in s-block homonuclear diatomic molecules.
s*2s
s2s
s*2s
s2s
Energy 2s 2s 2s
Be2
Li2
Be2 bond order = 0
Li2 bond order = 1

20. Contours and energies of s and p MOs through combinations of 2p atomic orbitals.

21. Relative MO energy levels for Period 2 homonuclear diatomic molecules.
without 2s-2p mixing
with 2s-2p mixing
MO energy levels for O2, F2, and Ne2
MO energy levels for B2, C2, and N2

22. MO occupancy and molecular properties for B2 through Ne2

23. The paramagnetic properties of O2