Molecular Shapes

1. Molecular Shapes

2. What is VSEPR?

3. VSEPR • Valence Shell Electron Pair Repulsion • The main idea is that electrons don’t like to hang around near each other because they repel each other. As a result, the atoms in a molecule tend to separate as far as they can because their bonds repel each other.

4. Shapes Linear Lone pairs : 0 A Lone Pair is a pair of electrons that are not involved with bonding

5. Shapes Bent Lone pairs : 2

6. Shapes Trigonal Planar Lone pairs : 0 This shape is typically formed with Boron. Boron is an exception to the octet rule and can be happy with only 6 valence electrons.

7. Shapes Trigonal Pyrimidal Lone pairs : 1

8. Shapes Tetrahedral Lone pairs : 0

9. Recap • Linear = 0 lone pairs • Bent = 2 lone pairs • Trigonal Planar = 0 lone pairs • Trigonal Pyramidal = 1 lone pair • Tetrahedral = 0 lone pairs

10. Polar covalent molecules: A type of bond that forms when electrons are not shared equally (nonsymmetrical) • Non polar molecules: A type of bond that forms when electrons are shared equally (symmetrical)

11. Polarity • Go back to page 6 and for each shape, include the following examples of when the shape is polar and non polar.

12. Shapes Linear can be Non-Polar OR Polar depending on if the outside atoms are similar or different. Linear Nonsymmetrical Polar Symmetrical Non-Polar

13. Shapes Bent This molecule is NOT symmetrical horizontally. Always Nonsymmetrical Polar

14. Shapes Trigonal Planar can be Non-Polar OR Polar depending on if the outside atoms are similar or different. Trigonal Planar Nonsymmetrical Polar Symmetrical Non-Polar

15. Shapes This molecule is NOT symmetrical horizontally. Trigonal Pyrimidal Lone pairs : 1 Always Nonsymmetrical Polar

16. Shapes Tetrahedral can be Non-Polar OR Polar depending on if the outside atoms are similar or different. Tetrahedral Nonsymmetrical Polar Symmetrical Non-Polar

17. Molecular Model Lab

18. Molecular Model Lab • On the next page in the Unit 6 Packet. • You will draw electron dot diagrams, and then build the molecules using the plastic models. • All of the holes need to be filled. • Use the longer “bendy” ones to make double bonds. • Each kit should have the exact number of atoms in order to make all of the molecules without having to take any apart. • Next Slide has the Color Key

19. Color Codes • White = hydrogen • Red = oxygen • Black = carbon • Blue = nitrogen • Green = chlorine

20. When you finish… In the space below the chart, draw these and determine the shape and polarity of these molecules without building them. • BF3 • CF4 • N2 • H2S • CS2 • C2H2