1. Theories of Covalent Bonding
Valence Bond (VB) Theory and Orbital Hybridization
The Mode of Orbital Overlap and the Types of Covalent Bonds

2. The Central Themes of VB Theory
Basic Principle
A covalent bond forms when the orbitals of two atoms overlap and the overlap region, which is between the nuclei, is occupied by a pair of electrons.
The two wave functions are in phase so the amplitude increases
between the nuclei.

3. 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.

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

5. 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

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

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

8. The sp2 hybrid orbitals in BF3.

9. The sp3 hybrid orbitals in CH4.

10. The sp3 hybrid orbitals in NH3.

11. The sp3 hybrid orbitals in H2O.

12. The sp3d hybrid orbitals in PCl5.

13. The sp3d2 hybrid orbitals in SF6.

15. 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

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

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

18. The paramagnetic properties of O2