1. 8-2.4 Hybrid Orbital Theory
Ⅰ. The Central Themes of
Hybridization Theory
Hybridization is the process of mixing
the atomic orbitals in an atom (usually
the central atom) to generate a set of
new atomic orbitals.

2. (2) The new atomic orbitals are called hybrid orbitals.
Hybrid orbital is atomic orbitals obtained
when two or more nonequivalent orbitals of
the same atom combine, are then used to form
covalent bonds.
(3) The number of hybrid orbitals generated is
equal to the number of atomic orbitals.
(4) The spatial orientation of these new orbitals
lead to more stable bonds and are consistent
with the observed molecular shapes.

3. The following points are useful for an understanding of hybridization
The concept of hybridization does not apply
to isolated atoms. It is used only to explain a
bonding scheme in a molecule.
(2) Hybrid orbital is not a pure atomic orbital.
Hybrid orbitals have very different shapes
from pure atomic orbitals.

4. (3) All the hybrid orbitals are equivalent in
every respect, except in their relative
orientations in space.
(4) Covalent bonds in polyatomic molecules
are formed by the overlap of a hybrid
orbital and a pure atomic orbital, or of
two hybrid orbitals.

5. Ⅱ. Types of Hybrid Orbitals
1. sp Hybridization
One s orbital and one p orbital form two sp hybrid orbital
Hybridization of all s orbital and a p orbital (of the
same atom) produce two sp hybrid orbitals. The two
sp hybrid orbitals have a linear arrangement.

6. two sp hybrid orbitals

7. BeCl2 molecules
4Be: 2s2 2p0 ↑↓ ↑↓
sp hybrid orbital

8. The sp hybrid orbitals in gaseous BeCl2
Be (excitated)
The sp hybrid orbitals in gaseous BeCl2

10. 2. sp2 Hybridization
One s orbital and two p orbital form three sp2 hybrid orbital

11. BF3 BF3 molecules 5B: 2s2 2p1 sp2-p sp2 hybrid orbital ↑ ↑↓ ↑↓ ↑↓ ↑↓ ↑

12. Figure: The sp2 hybrid orbitals in BF3

14. 3. sp Hybridization
One s orbital and three p orbital form four sp3 hybrid orbital

15. sp3-s σ
6C: 2s2 2p CH4 (methane) ↑↓ ↑↓ ↑↓ ↑↓
sp3 hybrid orbital

16. Figure: The sp3 hybrid orbitals in CH4

18. CH4

19. sp: BeCl2
sp2: BF3 , C2H4
sp3: CH4 , CCl4
Equivalent hybridization
Hybridization
Nonequivalent hybridization
sp3: NH3 , H2O

20. NH3 molecule Nonequivalent hybridization sp3 Hybrid orbital
Central atom N
7N: 1s2 2s2 2p3
sp3 Hybrid orbital
(one lone pair electrons)

21. Predict correct
bond angle

22. H2O molecule sp3 Hybrid orbital (two lone pair electrons)
Central atom O
8O: 1s2 2s2 2p4
sp3 Hybrid orbital
(two lone pair electrons)

23. bonding-pair vs. bonding
pair repulsion
lone-pair vs. bonding
<
lone-pair vs. lone pair
repulsion

24. H2O
NH3

25. sp2 Hybridization of Ethylene
6C: 2s2 2p CH2=CH2 (ethylene)
2py orbital
sp2 hybrid orbital

28. sp Hybridization of Acetylene
6C: 2s2 2p CH ≡ CH (acetylene) ↑↓ ↑↓ ↑↓ ↑↓ ↑ ↑
sp hybrid orbital

31. Geometry of the molecule
sp :180° linear
sp2 :120° trigonal planar
sp3 :109.5°tetrahedral
NH3 :107.3°
trigonal pyramidal
H2O :104.5°
Bent /Angular