### Unit 6 Molecular Geom and Bonding

```3 January 2012
Take Out Bonding Problem Set
 Objective: You will be able to:
 describe the VSEPR model and describe
molecular geometry for 2 to 4 electron
domains
Do now: On your white paper, across the top of a
long edge, draw the Lewis structures for:
1. carbon dioxide
2. boron trifluoride
3. methane
4. ammonia

Agenda
Homework Quiz
II. Collect Winter Break Homework
 We’ll do a review of intermolecular
forces after this current (short) unit
III. VSEPR Theory and Molecular Geometry
Homework: p. 453 #1, 2, 7, 9, 12 (please
sketch neatly!): tomorrow
I’ll collect the Intermolecular Forces problem
set tomorrow. See me after school with
questions!
I.
Keys?
The VSEPR Model
Valence-shell electron-pair
repulsion (VSEPR) model: a way to
use Lewis structures to determine the
geometries (shapes) of molecules.
 based on repulsive forces that exist
between electron pairs within molecules
 geometry: the arrangement of a
molecule’s atoms in three-dimensional
space

bond angle: an angle made by the lines
joining the nuclei of atoms in a molecule
 electron domain: a region around an
atom in which electrons will most likely be
found.
 produced by a non-bonding pair, a
single bond, a double bond or a triple
bond

Activity
1.
2.
3.
On your white paper, across the top of a long
edge, draw the Lewis structures for:
1. carbon dioxide
2. boron trifluoride
3. methane
4. ammonia
Then, with your knowledge of the VSEPR
theory, construct models for each molecule
that predict it’s 3D geometry. Sketch these
below each Lewis structure.
Measure and label the bond angles.
Linear
2 bonding domains
0 non-bonding domains
180o
Trigonal Planar
3 bonding domains
0 non-bonding domains
120o
Non-linear (bent)
2 bonding domains
1 non-bonding domain
117o
Tetrahedral
4 bonding domains
0 non-bonding domains
109.5o
Trigonal pyramidal
3 bonding domains
1 non-bonding domain
107o
Non-linear (bent)
2 bonding domains
2 non-bonding domains
104o
Label the shapes of the four molecules you
 Draw Lewis structures for
 NO2 H2O
 Determine their shape. Build the model.
 Draw a sketch, label the shape name and
the bond angle.

Next Up

What about molecules with 5 or 6 electron
domains?!
Homework

p. 453 #1, 2, 7, 9, 12: tomorrow
4 January 2012
Take Out: Problem sets, p. 453 Homework
 Objective: You will be able to:
 use VSEPR theory to determine the shapes
of molecules with five and six electron
domains around the central atom.
 Homework Quiz: Draw the Lewis
structure, determine the shape, sketch, label
the bond angle: HCF3
 Bonus: Describe the polarity of this
molecule.

Agenda
Homework Quiz
III. Shapes of molecules with five and six
electron domains: Notes
IV. Polarity?
 Homework: p. 453 #7d, 8, 10, 12d, e, g,
13, 14: Mon.
 read p. 420-423, ignore equations: Mon.
I.
Draw Lewis Structures for…
PCl5
 SF4
 ClF3
 XeF2

Electron-Domain Geometry

Trigonal bipyramidal: 5 electron domains
 trigonal bipyramidal (5 bonding, 0 non)
 seesaw (4, 1)
 T-shaped (3, 2)
 Linear (2, 3)
Draw Lewis Structures for…
SF6
 BrF5
 XeF4

Electron-Domain Geometry

Octahedral: 6 electron domains
 octahedral (6 bonding, 0 non)
 square pyramidal (5, 1)
 square planar (4, 2)
9 January 2012
Take Out Homework
 Objective: You will be able to:
 identify and describe the polarity of
bonds and molecules
 Homework Quiz: a. Draw a Lewis
Structure b. Identify the shape c.
Sketch
 a. IBr3
b. SI6

Agenda
Homework Quiz
III. Polarity Notes and Practice Problems
IV. Hand back assignments
Homework: p. 454 #18, 20, 23
finish polarity practice problems
I.
Practice Problems

Draw Lewis Structures, predict geometry
(electron domain and molecular), sketch,
label:
 PBr5
 SI6
 ClF4+
 SF5 BCl3
 IBr3
 XeCl2
Polarity

bond polarity: a measure of how equally
the electrons in a bond are shared between
two atoms.
 the greater the difference in
electronegativity of the bonded atoms, the
more polar the bond.

dipole moment: measure of the charge
separation in a molecule; how polar the
entire molecule is
 the vector sum of all the bond dipoles
Examples
HCl
 BF3
 CCl4
 NH3
 CH3Cl

Examples

C2H2Cl2
Practice Problems
1.
 2.
 3.
 4.
 5.
 6.
 7.
 8.

SO2
CCl4
CHCl3
TeCl2
CO32NH3
SO42CO2
9. BF3
10. SF3+
11. XeF2
12. BrF5
13. XeF4
14. SeF4
15. ClF3
16. SeF6
Homework



p. 454 #18, 20, 23
finish polarity practice problems
10 January 2012



Take Out Homework
Objective: You will be able to:
 describe and identify hybridization of
orbitals in molecules and describe and
count sigma and pi bonds.
Homework Quiz: SF3+ a. Draw the shape
and label with the shape name. b. Indicate
bond moments. c. Indicate dipole moment,
if any. d. Polar or non polar?
Agenda
Homework Quiz
2. Hybridization Notes and Practice
Problems
3. Sigma and Pi Bond Notes and Practice
Problems
Homework: p. 454 #31, 32, 34, 35, 37, 39,
40, 41, 42, 69, 71, 75, 82, 99 b0nus: 100:
Thurs.
1.
Hybridization
VSEPR Theory Review
Valence electrons only are involved in
bonding.
 Non-bonding and bonding electron pairs
around the central atom repel each other.
 This repulsion causes specific shapes and
bond angles for each molecule.

Question
How can atoms, that have s, p and d orbitals,
bond in ways that make the molecule shapes?
o
 Ex: p orbitals at 90 angles to each other.
 How can they make a bond angle of 109.5o
in tetrahedral or 120o in trigonal planar??

?
Energy
1s
2s
2p
Carbon
1s
Hydrogen
How can carbon make four bonds with
four hydrogen atoms?? How can those
bonds be at 109.5o (tetrahedral)?

sublevels in an atom’s outer shell
recombine into new orbitals of
equal energy with different shapes
and angles.
Energy
1s
sp3 hybrid orbital
• Hybridization: the mixing of atomic orbitals in an
atom (usually the central atom) to generate a set
of hybrid orbitals.
Energy
Energy
1s
2s
2p
Carbon
1s
sp3 hybrid orbital

1s
Hydrogen
Total energy the same, but
redistributed
Animation
DRxS6k
 http://www.mhhe.com/physsci/chemistry
/essentialchemistry/flash/hybrv18.swf

sp3 Example

CH4
sp hybridization

BeCl2
12 January 2012

Objective: You will be able to:
 describe and identify hybridization of
orbitals in molecules and describe and
count sigma and pi bonds.
 review bonding and molecular geometry.
Agenda
Hybridization notes
 Practice problems
 Sigma and pi bond notes and examples
 Problem Set work time
Homework: p. 454 #31, 32, 34, 35, 37, 39,
40, 41, 42, 69, 71, 75, 82, 99 b0nus: 100:
Tues.
Problem Set: Tues
Test Weds.

sp2 hybridization

BF3
Shapes of hybrid orbitals
s, p
s, p, p
trigonal
pyramidal
s, p, p, p

NH3 is also sp3 hybridization:
three orbitals for the H, one orbital
for the non-bonding pair.
Steps to Determine Hybridization
1.
2.
3.
Draw the Lewis structure
Predict the molecule shape using the
VSEPR theory
Determine hybridization by matching the
arrangement of the molecule with known
examples (table 10.4)



1.
2.
3.
4.
5.
6.
7.
For each compound’s central atom, draw the
orbital notation.
Then, draw the orbital notation after
hybridization.
Name the type of hybridization and the shape of
each molecule.
BeH2
AlI3
PF3
SiF4
CO2
PH3
H2O
Multiple Bonds

When a double bond forms, the
two bonds are not exactly the
same.
First: “end on” s-orbital
interaction: σ (sigma) bonds
Second: “side on” p-orbital
interaction: π (pi) bonds
Single bonds: always σ bonds.
 Double bonds: one σ + one π bond.
 Triple bonds: one σ bond +two π
bonds


Count sigma and pi bonds
 CHCl3
 SCO
 SeO2
 ClO3-
Practice Problems
Count the total number of sigma and pi
bonds in each molecule
 Draw a Lewis structure first!
1. H2CO
2. O2
3. CO2
4. HCN (C is the central atom)
5. CSN- (C is the central atom)
6. N3
Homework

p. 454 #31, 32, 34, 35, 37, 39, 40, 41, 42, 69,
71, 74, 75, 82, 99 b0nus: 100: Thurs.
17 January 2012


a.
b.
c.
Objective: You will be able to:
 review chemical bonding and molecular
geometry for a test.
Homework Quiz: For the molecule on the
board:
Describe/label bond moments and dipole
moment, if any.
Describe the hybridization around each C
atom
How many sigma bonds? Pi?
Agenda
Homework quiz
II. Questions on problem set/homework?
III. Collect problem set
IV. Midterm Review
Homework: Unit 6 test tomorrow
I.
Unit 6 Test
12 multiple choice
 1 four-part free response
 1 period!!

Midterm Exam
26 multiple choice, no calc.
II. 2 predict products/write equation
III. 2 multi-part free response, with calc.
 110 minutes
I.
Textbook Homework

Questions?
Problem Set

Questions?
Homework
Study for Unit Test
 Midterm Review starts Thursday

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