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 dioxide2. boron trifluoride3. methane4. ammonia
Agenda
I. Homework QuizII. Collect Winter Break Homework
We’ll do a review of intermolecular forces after this current (short) unit
III. VSEPR Theory and Molecular GeometryHomework: p. 453 #1, 2, 7, 9, 12 (please
sketch neatly!): tomorrowI’ll collect the Intermolecular Forces
problem set tomorrow. See me after school with questions!
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. On your white paper, across the top of a long edge, draw the Lewis structures for:
1. carbon dioxide2. boron trifluoride3. methane4. ammonia
2. 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.
3. Measure and label the bond angles.
Linear2 bonding domains0 non-bonding domains
180o
Trigonal Planar3 bonding domains0 non-bonding domains120o
Non-linear (bent)2 bonding domains1 non-bonding domain117o
Tetrahedral4 bonding domains0 non-bonding domains109.5o
Trigonal pyramidal3 bonding domains1 non-bonding domain107o
Non-linear (bent)2 bonding domains2 non-bonding domains104o
On your paper
Label the shapes of the four molecules you already constructed
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
I. Homework QuizII. Homework AnswersIII. Shapes of molecules with five and
six electron domains: NotesIV. Polarity? Homework: p. 453 #7d, 8, 10, 12d,
e, g, 13, 14: Mon. read p. 420-423, ignore equations:
Mon.
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
I. Homework QuizII. Homework AnswersIII. Polarity Notes and Practice
ProblemsIV. Hand back assignmentsHomework: p. 454 #18, 20, 23finish polarity practice problemsread p. 428-436
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. SO2 9. BF3
2. CCl4 10. SF3+
3. CHCl3 11. XeF2
4. TeCl2 12. BrF5
5. CO32- 13. XeF4
6. NH3 14. SeF4
7. SO42- 15. ClF3
8. CO2 16. SeF6
Homework
p. 454 #18, 20, 23 finish polarity practice problems read p. 428-436
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
1. Homework Quiz2. Hybridization Notes and Practice
Problems3. Sigma and Pi Bond Notes and
Practice ProblemsHomework: p. 454 #31, 32, 34, 35,
37, 39, 40, 41, 42, 69, 71, 75, 82, 99 b0nus: 100: Thurs.
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?
Ex: p orbitals at 90o angles to each other. How can they make a bond angle of
109.5o in tetrahedral or 120o in trigonal planar?? ?
37
1s 2s 2p 1s Carbon Hydrogen
How can carbon make four bonds with four hydrogen atoms?? How can those bonds be at 109.5o (tetrahedral)?
En
erg
y
Answer: Hybrid orbitals: the sublevels in an atom’s outer shell recombine into new orbitals of equal energy with different shapes and angles.
1s sp3 hybrid orbital
En
erg
y
• Hybridization: the mixing of atomic orbitals in an atom (usually the central atom) to generate a set of hybrid orbitals.
Total energy the same, but redistributed
39
1s 2s 2p 1s Carbon Hydrogen
En
erg
y
1s sp3 hybrid orbital
En
erg
y
Animation
http://www.youtube.com/watch?v=g1fGXDRxS6k
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 timeHomework: p. 454 #31, 32, 34, 35, 37,
39, 40, 41, 42, 69, 71, 75, 82, 99 b0nus: 100: Tues.
Problem Set: TuesTest Weds.
sp2 hybridization
BF3
Shapes of hybrid orbitals
s, p
s, p, p
s, p, p, ptrigonal pyramidal
NH3 is also sp3 hybridization: three orbitals for the H, one orbital for the non-bonding pair.
Steps to Determine Hybridization
1. Draw the Lewis structure2. Predict the molecule shape using
the VSEPR theory3. Determine hybridization by
matching the arrangement of the molecule with known examples (table 10.4)
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.
1. BeH2
2. AlI3
3. PF3
4. SiF4
5. CO2
6. PH3
7. 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
Objective: You will be able to: review chemical bonding and
molecular geometry for a test. Homework Quiz: For the molecule on
the board:a. Describe/label bond moments and
dipole moment, if any.b. Describe the hybridization around each
C atomc. How many sigma bonds? Pi?
Agenda
I. Homework quizII. Questions on problem
set/homework?III. Collect problem setIV. Midterm ReviewHomework: Unit 6 test tomorrow
Unit 6 Test
12 multiple choice 1 four-part free response 1 period!!
Midterm Exam
I. 26 multiple choice, no calc.II. 2 predict products/write equationIII. 2 multi-part free response, with
calc. 110 minutes
Textbook Homework
Questions?
Problem Set
Questions?
Homework
Study for Unit Test Midterm Review starts Thursday