this is a teory of physics

1. VSEPR THEORY:VSEPR THEORY:
How do we determineHow do we determine
the shapes ofthe shapes of
molecules and ions?molecules and ions?

2. VSEPR THEORYVSEPR THEORY
What does VSEPR standWhat does VSEPR stand
for?for?
VValencealence SShellhell EElectronlectron
PPairair RRepulsionepulsion

3. VSEPR THEORYVSEPR THEORY
Why is this important toWhy is this important to
know?know?
It explains how moleculesIt explains how molecules
and ions behave.and ions behave.

4. VSEPR THEORYVSEPR THEORY
For example:For example:
It explains why waterIt explains why water
molecules are so good atmolecules are so good at
dissolving ionic substancesdissolving ionic substances
even though water doeseven though water does
not have an ionic bond.not have an ionic bond.

5. VSEPR THEORYVSEPR THEORY
Another example:Another example:
It explains whyIt explains why part of apart of a
soap molecule attractssoap molecule attracts
waterwater whilewhile the other partthe other part
attracts grease and oils.attracts grease and oils.

6. VSEPR THEORYVSEPR THEORY
Another example: Use it toAnother example: Use it to
clean up greasy handsclean up greasy hands
from working on your carfrom working on your car
or sprucing up your nailsor sprucing up your nails
between manicures!between manicures!

7. VSEPR THEORY:VSEPR THEORY:
Basic procedureBasic procedure
1)1) Determine the centralDetermine the central
atomatom (usually the atom(usually the atom
with the lowest subscriptwith the lowest subscript
and/or the atom capable ofand/or the atom capable of
forming the most bonds).forming the most bonds).

8. VSEPR THEORY:VSEPR THEORY:
Basic procedureBasic procedure
2)2) Draw the electron dotDraw the electron dot
structure and bar diagramstructure and bar diagram

9. VSEPR THEORY:VSEPR THEORY:
Basic procedureBasic procedure
3)3) Determine the molecularDetermine the molecular
geometry using ALLgeometry using ALL
electron pairs AND atomselectron pairs AND atoms
around the central atom.around the central atom.

10. VSEPR THEORY:VSEPR THEORY:
Basic procedureBasic procedure
4)4) Modify the geometry toModify the geometry to
determine the molecular shape ifdetermine the molecular shape if
non-bonding electron pairs existnon-bonding electron pairs exist
by ignoring them,by ignoring them, BUT LEAVEBUT LEAVE
THE ATOMS OF BONDED PAIRSTHE ATOMS OF BONDED PAIRS
WHERE THEY ARE.WHERE THEY ARE. This is doneThis is done
because even if the electrons have nobecause even if the electrons have no
atom attached, these unbonded electronatom attached, these unbonded electron
pairs still affect the shape of the structure.pairs still affect the shape of the structure.

11. VSEPR THEORY:VSEPR THEORY:
Example: BeHExample: BeH22
1) Central Atom?1) Central Atom?
BeBe (only 1 atom)(only 1 atom)

12. VSEPR THEORY:VSEPR THEORY:
Example: BeHExample: BeH22
2) Electron Dot?2) Electron Dot?
2) Bar Diagram?2) Bar Diagram?
H Be H
H—Be—H
Note that
Be violates
the octet
rule—this is
an
exception!

13. VSEPR THEORY:VSEPR THEORY:
Example: BeHExample: BeH22
3) Geometry? Hint: What is3) Geometry? Hint: What is
the furthest apart you canthe furthest apart you can
spread two atoms attachedspread two atoms attached
to a central atom?to a central atom?
H HBe

14. VSEPR THEORY:VSEPR THEORY:
Example: BeHExample: BeH22
4) Shape? Ignore any4) Shape? Ignore any
unbonded pairs of electronsunbonded pairs of electrons
—not necessary in this case.—not necessary in this case.
 LINEARLINEAR
H HBe

15. VSEPR THEORY:VSEPR THEORY:
Example: BFExample: BF33
1) Central Atom?1) Central Atom?
BB (only 1 atom)(only 1 atom)

16. VSEPR THEORY:VSEPR THEORY:
Example: BFExample: BF33
2) Electron Dot?2) Electron Dot?
2) Bar Diagram?2) Bar Diagram?
F—B—F
F
Note that B
violates the
octet rule—
this is an
exception!
F B F
F

17. VSEPR THEORY:VSEPR THEORY:
Example: BFExample: BF33
3) Geometry? Hint: What is3) Geometry? Hint: What is
the furthest apart you canthe furthest apart you can
spread three atoms attachedspread three atoms attached
to a central atom?to a central atom?
B
F
F
F

18. VSEPR THEORY:VSEPR THEORY:
Example: BFExample: BF33
4) Shape? Ignore any4) Shape? Ignore any
unbonded pairs of electronsunbonded pairs of electrons
—not necessary in this case.—not necessary in this case.
 trigonal planartrigonal planar
B
F
F
F

19. VSEPR THEORY:VSEPR THEORY:
Example: CHExample: CH44
1) Central Atom?1) Central Atom?
CC (only 1 atom)(only 1 atom)

20. VSEPR THEORY:VSEPR THEORY:
Example: CHExample: CH44
2) Electron Dot?2) Electron Dot?
2) Bar Diagram?2) Bar Diagram?
H C H
H
H
H—C—H
H
H

21. VSEPR THEORY:VSEPR THEORY:
Example: CHExample: CH44
 3) Geometry? Hint: What is the3) Geometry? Hint: What is the
furthest apart you can spread fourfurthest apart you can spread four
atoms attached to a central atom?atoms attached to a central atom?
Think in 3D!Think in 3D!
C
HH
H
H

22. VSEPR THEORY:VSEPR THEORY:
Example: CHExample: CH44
 4) Shape? Ignore any unbonded4) Shape? Ignore any unbonded
pairs of electrons —not necessarypairs of electrons —not necessary
in this case.in this case.
 tetrahedraltetrahedral
C
HH
H
H

23. VSEPR THEORY:VSEPR THEORY:
Example: NHExample: NH33
1) Central Atom?1) Central Atom?
NN (only 1 atom)(only 1 atom)

24. VSEPR THEORY:VSEPR THEORY:
Example: NHExample: NH33
2) Electron Dot?2) Electron Dot?
2) Bar Diagram?2) Bar Diagram?
H N H
H
H—N—H
H

25. VSEPR THEORY:VSEPR THEORY:
Example: NHExample: NH33
 3) Geometry? Hint: What is the3) Geometry? Hint: What is the
furthest apart you can spread threefurthest apart you can spread three
atoms plus one unbonded pair ofatoms plus one unbonded pair of
electrons attached to a central atom?electrons attached to a central atom?
Think in 3D!Think in 3D!
H
N
HH
~109.5o

26. VSEPR THEORY:VSEPR THEORY:
Example: NHExample: NH33
 4) Shape? Ignore any unbonded4) Shape? Ignore any unbonded
pairs of electrons —it ISpairs of electrons —it IS
necessary in this case.necessary in this case.
 trigonaltrigonal
pyramidalpyramidal
H
N
HH
~109.5o

27. VSEPR THEORY:VSEPR THEORY:
Example: HExample: H22OO
1) Central Atom?1) Central Atom?
OO (only 1 atom)(only 1 atom)

28. VSEPR THEORY:VSEPR THEORY:
Example: HExample: H22OO
2) Electron Dot?2) Electron Dot?
2) Bar Diagram?2) Bar Diagram?
O H
H
O—H
H

29. VSEPR THEORY:VSEPR THEORY:
Example: HExample: H22OO
 3) Geometry? Hint: What is the3) Geometry? Hint: What is the
furthest apart you can spread twofurthest apart you can spread two
atoms plus two unbonded pairs ofatoms plus two unbonded pairs of
electrons attached to a central atom?electrons attached to a central atom?
Think in 3D!Think in 3D!
H
O
H
~109.5o

30. VSEPR THEORY:VSEPR THEORY:
Example: HExample: H22OO
 4) Shape? Ignore any unbonded4) Shape? Ignore any unbonded
pairs of electrons —it ISpairs of electrons —it IS
necessary in this case.necessary in this case.
 bentbent
H
O
H
~109.5o

31. VSEPR THEORYVSEPR THEORY
In conclusion:In conclusion:
Since water (also called theSince water (also called the
universal solvent) is bent ituniversal solvent) is bent it
is able to dissolve ionicis able to dissolve ionic
substances:substances:

32. O side
tends to
be – (the
electron
pairs
hybridize
into one
group)
H sides
tend to
be +
H
O
H

33. H
O
H
This
negative
side
tends to
attract
positive
ions
These
positive
ends
tend to
attract
negative
ions