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Topic: Molecular Shape Do Now: Draw Lewis Dot Diagram for the following two compounds 1. CH 2 F 2 2. CaO [ Ca ] +2.

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Presentation on theme: "Topic: Molecular Shape Do Now: Draw Lewis Dot Diagram for the following two compounds 1. CH 2 F 2 2. CaO [ Ca ] +2."— Presentation transcript:

1 Topic: Molecular Shape Do Now: Draw Lewis Dot Diagram for the following two compounds 1. CH 2 F 2 2. CaO [ Ca ] +2

2 Use the Lewis Structure Lewis structure is 2-D, but can help figure out 3-D shape H O H

3 REMINDER:Bonding Capacity 00:Ne: Ne, Ar, Kr 22·O: O, S 33·N· N, P 44·C· C, Si 11·F: F, Cl, Br, I 11HH Bonding Capacity # Unpaired Electrons Lewis Structure Atom · ··

4 Molecular Shape Determined by overlap of orbitals Shape determined by two factors: 1. # e - groups (pairs) around the central atom – pay close attention to the “free electron pairs” 2. total # atoms bonded to central atom Free electron pairs Central Atom

5 VSEPR (A model used to predict the shape of individual molecules based on the extent of electron-pair electrostatic repulsion) VSEPR= Valence shell electron pair repulsion: –Basically free electrons will repel one another causing the molecule to bend

6 2 atoms (no central atom) Always linear –Examples H 2 O 2 N 2 HCl

7 3 atoms Can be linear or bent –Must look at central atom If free electrons, then will be bent Central atom No free electrons so linear Central atom Free electrons so bent

8 4 atoms that form triangles Look at central atom –No free electrons = trigonal planar - Free electrons = trigonal pyramidal

9 4-Atom Molecules: Planar = no real central atom, no free electrons either

10 5 atom molecules Always tetrahedral –Examples CCl 4 CH 4 CH 2 I 2

11 Summary of Molecular Shapes Start with Lewis Structure! Look at total number of atoms Look at # of atoms bonded to central atom Look at free pair(s) of electrons around central atom

12   SymmetricalMolecules  Nonpolar Nonpolar

13 Asymmetric Molecules  Polar  Bent & trigonal pyramidal are always polar

14 Let’s try a few… Name the SHAPE and POLARITY

15 BENT POLAR

16 Trigonal Planar POLAR

17 Tetrahedral POLAR

18 Trigonal Pyramidal POLAR

19 linear POLAR

20 linear POLAR

21 bent POLAR

22 tetrahedral NONPOLAR


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