Molecular Geometry

bond length, angle determined experimentallyLewis structures bonding

geometryVSEPR

Valence Shell Electron Pair Repulsion

octahedron 90o bond angles

trigonal bipyramid equatorial 120o

axial 180o

big groupssmall groups

tetrahedron 109.5o

trigonal planar 120o

linear 180o

geometry apply to Chemistry

linear 180o

BeCl2

valence e- = 2 + (2 x 7) = 16e-

Cl....

..BeCl....

..

fewer than 8e-

valence pairs on Be bonding e-

linear molecule

two

linear 180o

CO2

valence e- = 4 + (2 x 6) = 16e-

CO....

.. O....

.. CO..

O..

.. ..

valence pairs on C ignore double bondstwo

single and double bonds same

linearmolecular shapemolecular geometry linear

trigonal planar 120o

SO2

valence e- = 6+ (2 x 6) = 18e-

valence pairs on Sthree

one lone pairmolecular geometry

molecular shape bent

trigonal

S O....

..O....

:

SO....

.. O....

..:

SO...... O

..

..

:

two bonding pairs

< 120o

tetrahedral 109.5o

CH4

valence e- = 4+(4 x 1) = 8e-

valence pairs on Cfour C HH

H

H109.5o

molecular geometry

molecular shape tetrahedral

tetrahedral

tetrahedral 109.5o

NH3

valence e- = 5+ (3 x 1) = 8e-

valence pairs on Nfour N HH

H

:

< 109.5o

molecular geometry

molecular shape trigonal pyramid

tetrahedral

one lone pairthree bonding pairs

tetrahedral 109.5o

H2O

valence e- = 6+ (2 x 1) = 8e-

valence pairs on OfourO HH

::

< 109.5o

molecular geometry

molecular shape bent

tetrahedral

two lone pairtwo bonding pairs

bipyramidal 120o and 1800

PCl5

valence e- = 5+ (5 x 7) = 40e-

valence pairs on Pfive

molecular geometry

molecular shape bipyramidal

bipyramidal

P

Cl....

..

Cl....

..

Cl....

..Cl....

..

Cl

......

90o

120o

180o

bipyramidal 120o and 1800

SF4

valence e- = 6+ (4 x 7) = 34e-

valence pairs on Sfive

molecular geometry

molecular shape seesaw

bipyramidal

one lone pair

four bonding pairs S..F..

..

..F..

..

..F..

....F..

..

:

< 180o

bipyramidal 120o and 1800

ClF3

valence e- = 7+ (3 x 7) = 28e-

valence pairs on Clfive

molecular geometry

molecular shape T

bipyramidal

two lone pair

three bonding pairsCl

..F..

..

..F..

..

..F..

..

::

180o90o

bipyramidal 120o and 1800

ICl2-

valence e- = 7+ (2 x 7) + e-

valence pairs on Ifive

molecular geometry

molecular shape linear

bipyramidal

three lone pair on I

two bonding pairs

= 22e-

I..Cl..

..

::

..Cl..

..

:

octahedral 90o

BrF5

valence e- = 7+ (5 x 7)

valence pairs on Brsix

molecular geometry

molecular shape square pyramidal

octahedral

= 42e-

one lone pair

five bonding pairs

BrF....

..F....

..

F....

..

F....

..

F.... ..:

octahedral 90o

XeF4

valence e- = 8+ (4 x 7)

valence pairs on Xesix

molecular geometry

molecular shape square planar

octahedral

= 36e-

two lone pair

four bonding pairsXe

F....

..F....

..

F....

..

F....

..

:

:

Cl....

..BeCl....

..

SO....

.. O....

.. S O

....

..O.... SO

...... O

..

..

S

O O

:

CO....

.. O....

.. CO..

O..

.. ..

B

: :

F

:

: : F

:

::

F: ::

C HH

H

H

N HH

H

:

O HH

::

P

Cl....

..

Cl....

..

Cl....

..

Cl....

..

Cl

......

S..F..

..

..F..

..

..F..

..

..F..

..

:

Cl..F..

....F..

....F..

..

::

I..Cl..

..

::

..Cl..

..

:

F..

.. ..S

F....

..

F....

..

F....

..F....

..

F.... ..

BrF....

..

F....

..

F....

..F....

..

F.... ..:

XeF....

..

F....

..

F....

..

F....

..

:

: