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Lecture 11 - VSEPR Theory, Molecular Shape 5 Base e - pair geometries will predict 13 Molecular geometries STEPS FOR SUCCESS: 1.draw Lewis 2. bonding pairs.

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Presentation on theme: "Lecture 11 - VSEPR Theory, Molecular Shape 5 Base e - pair geometries will predict 13 Molecular geometries STEPS FOR SUCCESS: 1.draw Lewis 2. bonding pairs."— Presentation transcript:

1 Lecture 11 - VSEPR Theory, Molecular Shape 5 Base e - pair geometries will predict 13 Molecular geometries STEPS FOR SUCCESS: 1.draw Lewis 2. bonding pairs 3.lone pairs 4.multiple bonds count as one bonded pair

2 Resonance Structures e.g. O 3 (ozone) OOO.. : :

3 e.g. SO 3 OOOSOSOSOOOOOOOSOSOSOOOO

4 e.g. carbonate ion, CO 3 -2 OOOCOCOCOOOOOOOCOCOCOOOO -2

5 Molecules that don’t obey rules Case 2. Incomplete octets FBFFFBFF     H - Cl  

6 Molecules that don’t obey rules Case 3. Expanded Octets e.g. Phosphorus[Ne] 3s 2 3p 3 e.g. Sulfur[Ne] 3s 2 3p 4 e.gXenon[Ne] 3s 2 3p 6 3d sublevel is close in energy to 3p!

7 Molecules that don’t obey rules Case 3. Expanded Octets ClF ClFF ClPS ClFF ClF 10 electrons! 12 electrons!

8 Molecules that don’t obey rules Case 3. Expanded Octets Xe F F F F : : 12 electrons!

9 Predicting Molecular Shapes VSEPR Theory (Valence Shell Electron Pair Repulsion) - Electron clouds repel one another - Terminal atoms move as far apart as possible - Distinctive geometry results

10 VSEPR Step 1. - count the number of total electron pairs around the central atom - count # Bonding Pairs -count # Nonbonding or Lone Pairs Step 2. Predict the shape!

11 VSEPR ElectronBonds Lone NotationShape Pairs AX 2 linear AX 3 trigonal planar AX 2 Ebent

12 AX 2 e.g. CO 2 (Linear) O = C = O bond angle = 180 o

13 AX 3 e.g. BF 3 (trigonal planar) bond angle = 120 o B F F F

14 AX 2 E e.g. SO 2 (bent) bond angle = 105 o S O O :

15 VSEPR ElectronBonds Lone NotationShape Pairs AX 4 tetrahedral AX 3 E trigonal pyramidal AX 2 E 2 bent

16 AX 4 e.g. methane C     All angles o (tetrahedral)

17     AX 3 E e.g. ammonia o (trigonal pyramidal)

18 AX 2 E 2 e.g. water    o (bent)

19 VSEPR ElectronBonds Lone NotationShape Pairs AX 5 trigonal bipyramidal AX 4 E see-saw AX 3 E 2 T-shaped AX 2 E 3 Linear

20 AX 5 Cl ClP Cl ideal angles: 90 o, 120 o (trigonal bipyramidal)

21 AX 4 E FFSFFFFSFF : ideal angles: 90 o, 120 o (seesaw)

22 AX 3 E 2 Cl Cl I Cl : : ideal angles: 90 o (t-shaped)

23 AX 2 E 3 F Xe: F : : angle: 180 o (linear)

24 VSEPR ElectronBonds Lone NotationShape Pairss Pairs AX 6 octahedral AX 5 E square pyramidal AX 4 E 2 square planar

25 AX 6 FFFSFFFFFFSFFFFF all angles 90 o (octahedral)

26 AX 5 E FFFIFF:FFFIFF:FF all angles 90 o (square pyramidal)

27 AX 4 E 2 :F XeF : all angles 90 o (square planar)


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