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: carbon dioxide boron trifluoride methane ammonia

Agenda Homework Quiz Collect Winter Break Homework We’ll do a review of intermolecular forces after this current (short) unit 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!

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 On your white paper, across the top of a long edge, draw the Lewis structures for: carbon dioxide boron trifluoride methane 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

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 Homework Quiz Homework Answers Shapes of molecules with five and six electron domains: Notes 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… 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 Homework Answers Polarity Notes and Practice Problems Hand back assignments Homework: p. 454 #18, 20, 23 finish polarity practice problems read 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 Homework Quiz Hybridization Notes and Practice Problems 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.

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?? ?

Energy 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)?

Answer: Hybrid orbitals: the 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.

Total energy the same, but redistributed 1s 2s 2p 1s Carbon Hydrogen Energy 1s sp3 hybrid orbital Total energy the same, but redistributed 39

Animation http://www.youtube.com/watch?v=g1fGX 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 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)

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! H2CO O2 CO2 HCN (C is the central atom) CSN- (C is the central atom) 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: Describe/label bond moments and dipole moment, if any. Describe the hybridization around each C atom How many sigma bonds? Pi?

Agenda Homework quiz Questions on problem set/homework? Collect problem set Midterm Review Homework: Unit 6 test tomorrow

Unit 6 Test 12 multiple choice 1 four-part free response 1 period!!

Midterm Exam 26 multiple choice, no calc. 2 predict products/write equation 2 multi-part free response, with calc. 110 minutes

Textbook Homework Questions?

Problem Set Questions?

Homework Study for Unit Test Midterm Review starts Thursday