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Molecular Geometry (p. 232 – 236)

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Ch. 8 – Molecular Structure. Molecular Geometry (p. 232 – 236). A. VSEPR Theory. V alence S hell E lectron P air R epulsion T heory Electron pairs orient themselves in order to minimize repulsive forces. Lone pairs repel more strongly than bonding pairs!!!. A. VSEPR Theory.

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a vsepr theory
A. VSEPR Theory
  • Valence Shell Electron Pair Repulsion Theory
  • Electron pairs orient themselves in order to minimize repulsive forces
a vsepr theory3

Lone pairs repel more strongly than bonding pairs!!!

A. VSEPR Theory
  • Types of e- Pairs
    • Bonding pairs – form bonds
    • Lone pairs – nonbonding e-
    • Total e- pairs– bonding + lone pairs
a vsepr theory4

Bond Angle

Bond Angle

A. VSEPR Theory
  • Lone pairs reduce the bond angle between atoms
b determining molecular shape

Know the 13 common shapes

& their bond angles!

B. Determining Molecular Shape
  • Draw the Lewis Diagram
  • Tally up e- pairs on central atom (bonds + lone pairs)
    • double/triple bonds = ONE pair
  • Shape is determined by the # of bonding pairs and lone pairs
c common molecular shapes

BeH2

C. Common Molecular Shapes

2 total

2 bond

0 lone

→ Electronic Geometry = linear

Hybridization = sp

LINEAR

180°

c common molecular shapes7

BF3

C. Common Molecular Shapes

→ Electronic Geometry = trigonal planar

Hybridization = sp2

3 total

3 bond

0 lone

TRIGONAL PLANAR

120°

c common molecular shapes8

NO21-

C. Common Molecular Shapes

→ Electronic Geometry = trigonal planar

Hybridization = sp2

3 total

2 bond

1 lone

BENT

<120°

c common molecular shapes9

CH4

C. Common Molecular Shapes

→ Electronic Geometry = tetrahedral

Hybridization = sp3

4 total

4 bond

0 lone

TETRAHEDRAL

109.5°

c common molecular shapes10

NCl3

C. Common Molecular Shapes

→ Electronic Geometry = tetrahedral

Hybridization = sp3

4 total

3 bond

1 lone

TRIGONAL PYRAMIDAL

107°

<109.5°

c common molecular shapes11

H2O

C. Common Molecular Shapes

→ Electronic Geometry = tetrahedral

Hybridization = sp3

4 total

2 bond

2 lone

BENT

104.5°

<109.5°

c common molecular shapes12

PI5

C. Common Molecular Shapes

→ Electronic Geometry = trigonal bipyramidal

Hybridization = dsp3

5 total

5 bond

0 lone

TRIGONAL BIPYRAMIDAL

120°/90°

c common molecular shapes13

KrF4

C. Common Molecular Shapes

→ Electronic Geometry = trigonal bipyramidal

Hybridization = dsp3

5 total

4 bond

1 lone

SEESAW

<120°/<90°

c common molecular shapes14

ClF3

C. Common Molecular Shapes

→ Electronic Geometry = trigonal bipyramidal

Hybridization = dsp3

5 total

3 bond

2 lone

T-SHAPE

<90°

c common molecular shapes15

I31-

C. Common Molecular Shapes

→ Electronic Geometry = trigonal bipyramidal

Hybridization = dsp3

5 total

3 bond

2 lone

LINEAR

180°

c common molecular shapes16

SH6

C. Common Molecular Shapes

→ Electronic Geometry = octahedral

Hybridization = d2sp3

6 total

6 bond

0 lone

OCTAHEDRAL

90°

c common molecular shapes17

IF5

C. Common Molecular Shapes

→ Electronic Geometry = octahedral

Hybridization = d2sp3

6 total

5 bond

1 lone

SQUARE PYRAMIDAL

<90°

c common molecular shapes18

SF4

C. Common Molecular Shapes

→ Electronic Geometry = octahedral

Hybridization = d2sp3

6 total

4 bond

2 lone

SQUARE PLANAR

90°

d examples

O

O Se O

D. Examples
  • SeO3

3 total

3 bond

0 lone

E.G. = TRIGONAL

PLANAR

M.G. = TRIGONAL

PLANAR

120°

d examples20

H As H

H

D. Examples
  • AsH3

4 total

3 bond

1 lone

E.G. = TETRAHEDRAL

M.G. = TRIGONAL PYRAMIDAL

107° (<109.5°)

e hybridization
E. Hybridization
  • Provides information about molecular bonding and molecular shape
  • Several atomic orbitals mix to form same total of equivalent hybrid orbitals
e hybridization22
E. Hybridization
  • Carbon is common example (orbital diagram)
  • One of 2s electrons is promoted to 2p
  • 4 identical orbitals form sp3 hybridization
e hybridization23

Remember the subscript is the orbital, not e- configuration!

E. Hybridization
  • Other types of hybridization
    • Be – 2 ve- forms sp
    • Al – 3 ve- forms sp2
    • Si – 4 ve- forms sp3
    • Kr – 8 ve- forms dsp3
    • S – 6 ve- forms d2sp3

exceptions

f hybridization example
F. Hybridization Example
  • Compare shapes and hybrid orbitals:

PF3 PF5

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