Ch 8 molecular structure
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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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Ch 8 molecular structure l.jpg

Ch. 8 – Molecular Structure

Molecular Geometry(p. 232 – 236)


A vsepr theory l.jpg
A. VSEPR Theory

  • Valence Shell Electron Pair Repulsion Theory

  • Electron pairs orient themselves in order to minimize repulsive forces


A vsepr theory3 l.jpg

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 l.jpg

Bond Angle

Bond Angle

A. VSEPR Theory

  • Lone pairs reduce the bond angle between atoms


B determining molecular shape l.jpg

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 l.jpg

BeH2

C. Common Molecular Shapes

2 total

2 bond

0 lone

→ Electronic Geometry = linear

Hybridization = sp

LINEAR

180°


C common molecular shapes7 l.jpg

BF3

C. Common Molecular Shapes

→ Electronic Geometry = trigonal planar

Hybridization = sp2

3 total

3 bond

0 lone

TRIGONAL PLANAR

120°


C common molecular shapes8 l.jpg

NO21-

C. Common Molecular Shapes

→ Electronic Geometry = trigonal planar

Hybridization = sp2

3 total

2 bond

1 lone

BENT

<120°


C common molecular shapes9 l.jpg

CH4

C. Common Molecular Shapes

→ Electronic Geometry = tetrahedral

Hybridization = sp3

4 total

4 bond

0 lone

TETRAHEDRAL

109.5°


C common molecular shapes10 l.jpg

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 l.jpg

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 l.jpg

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 l.jpg

KrF4

C. Common Molecular Shapes

→ Electronic Geometry = trigonal bipyramidal

Hybridization = dsp3

5 total

4 bond

1 lone

SEESAW

<120°/<90°


C common molecular shapes14 l.jpg

ClF3

C. Common Molecular Shapes

→ Electronic Geometry = trigonal bipyramidal

Hybridization = dsp3

5 total

3 bond

2 lone

T-SHAPE

<90°


C common molecular shapes15 l.jpg

I31-

C. Common Molecular Shapes

→ Electronic Geometry = trigonal bipyramidal

Hybridization = dsp3

5 total

3 bond

2 lone

LINEAR

180°


C common molecular shapes16 l.jpg

SH6

C. Common Molecular Shapes

→ Electronic Geometry = octahedral

Hybridization = d2sp3

6 total

6 bond

0 lone

OCTAHEDRAL

90°


C common molecular shapes17 l.jpg

IF5

C. Common Molecular Shapes

→ Electronic Geometry = octahedral

Hybridization = d2sp3

6 total

5 bond

1 lone

SQUARE PYRAMIDAL

<90°


C common molecular shapes18 l.jpg

SF4

C. Common Molecular Shapes

→ Electronic Geometry = octahedral

Hybridization = d2sp3

6 total

4 bond

2 lone

SQUARE PLANAR

90°


D examples l.jpg

O

O Se O

D. Examples

  • SeO3

3 total

3 bond

0 lone

E.G. = TRIGONAL

PLANAR

M.G. = TRIGONAL

PLANAR

120°


D examples20 l.jpg

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 l.jpg
E. Hybridization

  • Provides information about molecular bonding and molecular shape

  • Several atomic orbitals mix to form same total of equivalent hybrid orbitals


E hybridization22 l.jpg
E. Hybridization

  • Carbon is common example (orbital diagram)

  • One of 2s electrons is promoted to 2p

  • 4 identical orbitals form sp3 hybridization


E hybridization23 l.jpg

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 l.jpg
F. Hybridization Example

  • Compare shapes and hybrid orbitals:

    PF3 PF5