4/16/2025
Contents
• (9.1) Hybridization and the localized electron model
• (9.2) The molecular orbital model
• (9.3) Bonding in homonuclear diatomic molecules
Chapter 9
Covalent Bonding: Orbitals
1
2
Hybridization – sp3 hybrid orbitals
Lewis Structure of CH4
• Theoretical expectations: The 2s and 2p orbitals of C have different energy.
Therefore, there should be two different types of C-H bonds in CH4.
• Experimental result: All C-H bonds in CH4 are identical
3
• Hybrid orbitals
• are made by mixing atomic orbitals
• may be sp3, sp2, sp, sp3d, and sp3d2
• all have the same energy
4
sp3 hybrid orbitals
Bonding in ammonia
• Gives a tetrahedral orbital arrangement
5
• Three sp3 orbitals are used to form bonds to the three hydrogen
atoms, and the fourth sp3 orbital holds the lone pair
6
1
4/16/2025
sp2 Hybridization and double bonds
Formation of sp2 Orbitals
• Gives a trigonal planar orbital arrangement
• Combination of one 2s and two 2p orbitals
7
8
sp2 Hybrid Orbitals
Example: Bonding in ethene (CH2=CH2)
• Notice the unhybridized p orbital shown with two lobes above and
below the plane containing the sp2 hybrid orbitals
9
• Sigma () sp2-sp2 hybrid orbital mixing
• Pi () bond: 2p-2p orbital mixing
10
sp Hybridization
sp Hybridization
• Formation of sp hybrid orbitals
• Involves one s and one p orbital
11
12
2
4/16/2025
sp Hybridized Carbon Atom
Example: N2
• Triple bond consists of a  bond and two  bonds
• A lone pair occupies an sp orbital on each nitrogen atom
13
• Orbitals of an sp Hybridized Carbon Atom
14
Example CO2
Example CO2
• Formation of sigma bonds in CO2
15
• Formation of pi bonds in CO2
16
Electron-Pair Geometry and Hybridization
dsp3 and d2sp3 Hybridization
• Linear electron-pair geometry = sp
• Trigonal planar electron-pair geometry = sp2
• Tetrahedral electron-pair geometry = sp3
• Trigonal bipyramidal electron-pair geometry = dsp3 (sp3d)
• Octahedral electron-pair geometry = d2sp3 (sp3d2)
17
• dsp3 (sp3d) – by mixing one d, one s, and three p orbital mixing – trigonal
bipyramidal arrangement of electron pairs
• d2sp3 (sp3d2) – by mixing two d, one s, three p orbital mixing –
octahedral arrangement of electron pairs
18
3
4/16/2025
Examples
19
4