Molecular Geometry

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After today, you should be able to…

• Explain Valence Shell Electron Pair

Repulsion Theory (VSEPRT)

• Use structural formulas to describe the

molecular geometry of molecules

• Identify the correct geometric name for

the shape of the molecule

• Identify approximate bond angles for

molecules

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Molecular Geometry

• Valence Shell Electron Pair

Repulsion Theory (VSEPR):The
electron pairs (both shared and
unshared) in the outermost energy
level try to get as far apart from
each other as possible.
–This determines the
shape of the molecule.

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Shape: Linear

2 atoms

– Example: H2

3 atoms

– Example: CO2

Central atom must have

NO unshared pairs

H

H

O

C

O

~180˚

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Shape: Bent

3 atoms

– Example: H2O

Central atom can have
one or two unshared

pairs of electrons

O

H

H

~104.5˚

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Shape: Trigonal Planar

4 atoms

– Example: CH2O

Central atom has
NO unshared pairs

C

O

H H

~120˚

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Shape: Pyramid

4 atoms

– Example: NH3

Central atom has
one unshared pair

N

H

~107.5˚

H

H

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Shape: Tetrahedral

5 atoms

– Example: CH4

Central atom has
NO unshared pairs

H

~109.5˚

H

C

H

H

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Shape: Trigonal Bipyramidal

• 6 atoms

– Example: PF5

Central atom has
NO unshared pairs

For elements in period 3 and

higher, when bonded to Cl or F,

will have an expanded octet.

P


F

F

F

F

~90˚

~120˚

F

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Summary of Shapes

Linear

Bent

Trigonal planar

Pyramid

Tetrahedral

Trigonal bipyramidal