test2packet-3302

# Alert if there are more than four atoms attached to

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Alert: If there are more than four atoms attached to the central atom, such as SF 6 , attach all six F atoms to the S. There will be 12 electrons around S and it will violate the octet rule by having 12 around the central atom. This happens occasionally. Step 3 Put eight dots around ALL atoms except H, which only needs 2. Again using water as an example, put two dots above the O and two dots below the O. With the two (-), that makes 8 electrons around the O and two around both H's. If Possible, your goal is to keep 8 electrons around each atom. 9

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Step 4 Count the number of electrons used in the drawing and compare it to the number of available valence electrons. A. The dots in the drawing equal the number of of valence electrons. If this happens, the drawing is correct. Using H 2 O as an example, the drawing has 8 dots and the valence electrons equal 8 so the drawing is correct. B. There are fewer dots in the drawing than the number of valence electrons. Add pairs of dots to the central atom (attach them to the chemical symbol which is in the middle of your drawing) until the dots on the drawing equal the number of valence electrons. C. The drawing has more dots than the number of valence electrons. Erase four dots( two dots from the central atom and two from one of the other atoms). Now put a second line between the central atom and the atom from which you erased two dots. The two lines between these atoms represent a double bond (four dots) and are shared by both atoms. If you still need to reduce the number of dots, repeat this procedure. 10
Draw Lewis Dot Drawing Name the molecular geometry ( example: Tetrahedral) _______________________________________________________________________ CH 4 ____valence electrons _______________________________________________________________________ _ ClF 3 ____valence electrons _______________________________________________________________________ _ CO 2 _____valence electrons _______________________________________________________________________ _ NH 3 _____valence electrons _______________________________________________________________________ _ PCl 5 _____valence electrons _______________________________________________________________________ _ H 2 O_____valence electrons

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_______________________________________________________________________ _ SF 4 _____valence electrons 11 _______________________________________________________________________ _ SiO 2 _____valence electrons _______________________________________________________________________ _ XeF 4 _____valence electrons _______________________________________________________________________ _ BrF 5 _____valence electrons _______________________________________________________________________ _ N 2 _____valence electrons _______________________________________________________________________ _ NO 3 - ( when determining valence electrons, add on extra for the (-) charge) ______valence electrons _______________________________________________________________________ _
SO 4 2- ( add two extra valence electrons for the 2- ) _____valence electrons _______________________________________________________________________ _ SF 6 _____valence electrons 12

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Answers CH 4 Tetrahedral ClF 3 T-shaped CO 2 Linear NH 3 Pyramidal PCl 5 Trigonal Bipyramidal H 2 O Bent SF 4 See-Saw SiO 2 Linear XeF 4 Square Planar BrF 5 Square Pyramidal N 2 Linear NO 3 - Trigonal Planar SO 4 2- Tetrahedral SF 6 Octahedral

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VSEPR Geometries “A” is the central atom, “X” is a bonded atom, and “E” is a nonbonded pair of electrons NOTE: “E” can be a nonbonded pair of electrons on the central atom or an extra pair of electrons which was added to the central atom. 13
Practice Test One Chapter 7: Lewis Dot and Molecular Geometry Molecule Lewis Dot Molecular Geometry ___________________________________________________________ 1. SiH 4 ____________________________________________________________ 2. NH 3 _____________________________________________________________ 3. KrF 4 ______________________________________________________________ 4. BiBr 5 _______________________________________________________________ 5. NO 3 - ________________________________________________________________ 6. ICl 3 _________________________________________________________________ 7. SiO 2 __________________________________________________________________ 8. SF 4 ___________________________________________________________________ 14

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Answers: ( Test one starting with SiH 4 ) 1.
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