1. Chemistry Do Now
Directions: In a 3-5 sentence paragraph, use carbon tetrafluoride (CF4) to explain how a molecule can have polar bonds but not be polar (no dipole moment).

2. Chemistry Do Now 11-9-17 Sample response
Even though carbon tetrafluoride’s bonds are polar covalent (ΔEN = 1.5), the molecule is symmetrical, meaning if you bisect the molecule, its left side is a mirror-image of its right side. The central carbon atom is forming four covalent bonds with the fluorine atoms. All four fluorine atoms are attracted to the bond pair electrons equally. As a result, the pull on the pairs of bond pair electrons cancel each other out resulting in a nonpolar molecule without a dipole moment.

3. Turn in your do now sheet from Tuesday-Thursday (Last 1st Qtr. Grade)

4. Reminders
1st Quarter ends TODAY, Thursday, November 9, 2017 (0 school days left)
I closed my grades YESTERDAY; however, if you have an assignment or two that was never submitted, you need to do so TODAY.

5. Homework – Copy!
Complete VSEPR worksheet, if unfinished.

6. Objective
Students will know the attraction and repulsion between electrons (lone pair and bond pairs) determines the geometric shape of the molecule according to the Valence Shell Electron Repulsion Theory by reading informational text on the VSEPR Theory, taking notes and by creating balloon models for each geometric shape.
Mastery Level: Each student will be able to explain the VSEPR Theory, create balloon models and predict the shape of molecules on the VSEPR with at least 60% accuracy.

7. VSEPR Vocabulary Words

8. Engage What does the term repulsion mean?
What does the term attraction mean?
What do you think determines the shape of a molecule?

9. Explore
VSEPR YouTube video
VSEPR Theory Website as visual

10. Explain – vsepr theory

11. Valence Shell Electron Pair Repulsion Theory
Chemistry
Unit III: Combining Atoms
November 9, 2017
Planar triangular
Valence Shell Electron Pair Repulsion Theory
Tetrahedral
Trigonal pyramidal
Bent

12. Molecular Shape
VSEPR theory assumes that the shape of a molecule is determined by the repulsion of electron pairs.

13. VSEPR Theory Based on Electron Dot (Lewis structures)
06/10/99
Based on Electron Dot (Lewis structures)
Theory predicts shapes of compounds
abbreviated VSEPR
VSEPR (pronounced “vesper”) stands for Valence Shell Electron Pair Repulsion
VSEPR predicts shapes based on electron pairs repelling (in bonds or by themselves)
Electrons around central nucleus repel each other. So, structures have atoms maximally spread out

14. Molecular Shapes
We’ve learned to draw Lewis structures and account for all the valence electrons in a molecule.
But: Lewis structures are two dimensional and molecules are 3 dimensional objects.
The 3D structure is absolutely critical for understanding molecules.

15. Molecular Shapes geometry & shape of molecule critical
we can easily predict the 3D structure of a molecule just by adding up:
bound atoms + lone pairs

16. What Determines the Shape of a Molecule?
atoms and lone pairs take up space and prefer to be as far from each other as possible
shape can be predicted from simple geometry
lone pair
bonds

17. “Things”
The central atom has four “things” around it. A “thing” is an atom or a lone pair of electrons.
# things = atoms plus lone pairs

18. Valence Shell Electron Pair Repulsion Theory (VSEPR)
“The best arrangement of a given number of things is the one that minimizes the repulsions among them.”

19. Geometries
number of
things arrangement geometry bond angles
These are the geometries for two through six things around a central atom.
You must learn these!

20. Geometries
All one must do is count the number of “things” in the Lewis structure.
The geometry will be that which corresponds to that number of “things.”

21. Molecular Geometries
The geometry is often not the shape of the molecule, however.
The “shape” is defined by the positions of only the atoms in the molecules, not the lone pairs.

22. Geometries vs. shape
Within each geometry, there might be more than one shape.

23. Linear geometry two things
things geometry atoms lone pairs shape example
In this geometry, there is only one molecular geometry: linear.
NOTE: If there are only two atoms in the molecule, the molecule will be linear no matter what the geometry is.

24. Trigonal Planar geometry 3 things
things geometry atoms lone pairs shape example
There are two molecular geometries:
Trigonal planar, if there are no lone pairs
Bent, if there is a lone pair.

25. Lone pairs and Bond Angle
Lone pairs are physically larger than atoms.
Therefore, their repulsions are greater; this tends to decrease bond angles in a molecule.

26. Multiple Bonds and Bond Angles
Double and triple bonds place greater electron density on one side of the central atom than do single bonds.
Therefore, they also affect bond angles.

27. Tetrahedral geometry 4 things
Things geometry atoms lone pairs shape example
There are three molecular geometries:
Tetrahedral, if no lone pairs
Trigonal pyramidal if one is a lone pair
Bent if there are two lone pairs

28. Trigonal Bipyramidal geometry 5 things
There are two distinct positions in this geometry:
Axial
Equatorial

29. Trigonal Bipyramidal geometry
Lower-energy conformations result from having lone pairs in equatorial, rather than axial, positions in this geometry.

30. Trigonal Bipyramidal geometry
Things geometry atoms lone pairs shape example
There are four distinct molecular geometries in this domain:
Trigonal bipyramidal
Seesaw
T-shaped
Linear

31. Octahedral geometry 6 things
Things geometry atoms lone shape example
pairs
All positions are equivalent in the octahedral domain.
There are three molecular geometries:

32. Balloon Models
Extend Part I.

33. VSEPR Theory Worksheet
Extend Part II.

34. Evaluation
Exit ticket: Explain the VSEPR Theory and how it is used to predict the shape of molecules. Then, use the molecule, H2S to show how to draw its Lewis dot diagram, determine the number of lone pair and bond pair electrons and how to use the VSEPR Theory to predict the final shape.