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Honors Chemistry Chapter 8.1 notes

Honors Chemistry Chapter 8.1 notes. “The Shapes of Small Molecules”. Legos: Does this bring back any good memories???. I. Molecular Geometry. A. Structural Formula 1. Ex: Ammonia NH 3 2. Boring, 2 Dimensional… B. Ball and Stick Model

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Honors Chemistry Chapter 8.1 notes

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  1. Honors ChemistryChapter 8.1 notes “The Shapes of Small Molecules”

  2. Legos:Does this bring back any good memories???

  3. I. Molecular Geometry • A. Structural Formula • 1. Ex: Ammonia NH3 • 2. Boring, 2 Dimensional… • B. Ball and Stick Model 1. Def – Ball represents atom’s nucleus and inner electrons. Sticks represent bonds between atoms. 2. 3-Dimensional! 3. Shapes are symmetrical. a. Equal distance separating atoms

  4. b. Why? • *electrons repel other electrons to form symmetry • 4. VSEPR Theory • a. Valence-shell electron pair repulsion theory • b. Def – in a small molecule, the pairs of electrons are arranged as far apart from each other as possible. • *Note: this does not apply in all situations! •  Ex: transition metals

  5. II. Molecular GeometryContinued… • Linear • 1. Def – straight line angles (180°) • 2. Ex: O2, HCl, CO2

  6. Trigonal Planer • 1. Def – Triangular and flat (120°) • 2. Ex: BCl3, • 3. Usually 1 central atom

  7. C. Tetrahedral • 1. Def – means shape with 4 surfaces (109.5°) • 2. Ex: CH4 • 3. Angle is not 90°! (Fig 8-7)

  8. Pyramidal or Trigonal Pyramidal • 1. Def – 3 corners with 1 pair of unshared electrons • 2. Bond Angle = 107° • 3. why? Unpaired electrons take up more room. • 4. Ex: NH3

  9. Bent • 1. Def – Not linear ! • 2. Bond Angle = 105° • 3. Ex: H2O

  10. Others… • 1. T-shaped  ClF3 • 2. Square Planar  XeF4 • 3. TrigonalBipyramidal  PF5 • 4. Octahedral  SF6

  11. 8.1 assignment • Identify the following molecular shapes and bond angles: a. H2O b. CF4 c. NCl3 d. CO2 e. NF3 f. BF3 g. HCN h. NO3 Bent – 105 Tetrahedral – 109.5 Trigonal pyramidal – 107 Linear – 180 Trigonal pyramidal – 107 Trigonal Planer – 120 Linear – 180 Trigonal Planer – 120

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