1. Valence Shell Electron Pair Repulsion Theory
Planar triangular
Valence Shell Electron Pair Repulsion Theory
Tetrahedral
Trigonal pyramidal
Bent

2. Molecular Shape
VSEPR theory assumes that the shape of a molecule is determined by the repulsion of electron pairs.

3. VSEPR Theory Based on Electron Dot (Lewis structures)
Theory predicts shapes of compounds
abbreviated VSEPR
VSEPR (pronounced “vesper”) stands for Valence Shell Electron Pair Repulsion
VSEPR predicts shapes based on electron pairs repelling (in bonds or by themselves)
Electrons around central nucleus repel each other. So, structures have atoms maximally spread out

4. VSEPR overview Names of Shapes: tetrahedral trigonal pyramidal Bent
Each shape has a name
(you will have to know these)
Names of Shapes:
tetrahedral
trigonal pyramidal
Bent
Linear
trigonal planar

5. Models
Tetrahedral
Triangular Planar
Bent or V
Linear
Trigonal pyramidal

6. methane, CH4
Tetrahedral
109.5°
Bonds are all evenly spaced electrons

7. ammonia NH3 .. .. .. .. Trigonal Pyramidal
Less repulsion between the bonding pairs of electrons

8. .. ..
water, H2O
109.5° (109.5°)
109.5° (107°)
109.5° (104.5°)

9. .. ..

10. Bent or V
2 unshared pairs of e’s at top of O repel bonds and force them to bend

11. Number of electron pairs
SHAPE
Molecule
Lewis Structure
Number of electron pairs
CH4
NH3 4
Tetrahedral
Trigonal Pyramidal 4
(3 shared
1 lone pair)

12. Number of electron pairs
Molecule
Lewis Structure
Number of electron pairs
H2O
SHAPE
Bent or V 4
(2 shared
2 lone pairs)
Linear
CO2 2

13. Number of electron pairs
SHAPE
Molecule
Lewis Structure
Number of electron pairs
BeCl2
BF3
Linear 2
Trigonal Planar 3

14. HYBRIDIZATION

15. Hybridization – mixing of two or more atomic orbitals to form a new set of hybrid orbitals.
Mix at least 2 nonequivalent atomic orbitals (e.g. s and p). Hybrid orbitals have very different shape from original atomic orbitals.
Number of hybrid orbitals is equal to number of pure atomic orbitals used in the hybridization process.
Covalent bonds are formed by:
Overlap of hybrid orbitals with atomic orbitals
Overlap of hybrid orbitals with other hybrid orbitals
10.4

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sp3 Hybridization
Combination of one s and three p orbitals.
Tetrahedral – or 4 equal “attachments”
Remember: 1 bond has 2 electrons…..and 1 lone pair has 2 electrons. Therefore, they are equal.
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17. The Formation of sp3 Hybrid Orbitals
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18. Tetrahedral Set of Four sp3 Orbitals
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sp2 Hybridization
Combination of one s and two p orbitals.
Trigonal Planer – 3 equal attachments.
One p orbital is not used.
Oriented perpendicular to the plane of the sp2 orbitals.
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Sigma () Bond
Electron pair is shared in an area centered on a line running between the atoms.
SINGLE BOND
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Pi () Bond
Forms double and triple bonds by sharing electron pair(s) in the space above and below the σ bond.
Uses the unhybridized p orbitals.
DOUBLE OR TRIPLE BOND
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sp Hybridization
Combination of one s and one p orbital.
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When One s Orbital and One p Orbital are Hybridized, a Set of Two sp Orbitals Oriented at 180 Degrees Results
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The Orbitals for CO2
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sp3d Hybridization
Combination of one d, one s, and three p orbitals.
Gives a trigonal bipyramidal arrangement of five equivalent hybrid orbitals.
Recently disproven
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26. The Orbitals Used to Form the Bonds in PCl5
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sp3d2 Hybridization
Combination of two d, one s, and three p orbitals.
Gives an octahedral arrangement of six equivalent hybrid orbitals.
Recently disproven
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28. How is the Xenon Atom in XeF4 Hybridized?
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Concept Check
Draw the Lewis structure for HCN.
Which hybrid orbitals are used?
Draw HCN:
Showing all bonds between atoms.
Labeling each bond as  or .
sp hybrid orbitals are used in the bonding of HCN. Two sigma bonds and two pi bonds are present.
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