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What did you discover from the shape lab?

What did you discover from the shape lab?. What factors influence the shape of a molecule? Be ready to give an example of a molecule that backs up your statement. Shapes of Molecules/Compounds. Determined by presence of electrons… Electrons will repel each other Ionic substances

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What did you discover from the shape lab?

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  1. What did you discover from the shape lab? • What factors influence the shape of a molecule? Be ready to give an example of a molecule that backs up your statement.

  2. Shapes of Molecules/Compounds • Determined by presence of electrons… • Electrons will repel each other • Ionic substances don’t form molecules Ions stack together, anions alternating with cations

  3. The structure of Ionic solids

  4. The shape of the molecule is determined by the repulsion between the electrons that the atoms share Example: BH3 There will be three bonds of 120 degrees so that the bonding electrons can be as far apart as possible.

  5. A Lewis dot drawing cannot accurately show 3-dimensional shapes

  6. VSEPR Theory Valence Shell Electron Pair Repulsion The shape of a molecule is determined by the repulsion between the electrons of the bonded atoms The number of bonding pairs influences this shape (NOTE DOUBLE AND TRIPLE BONDS ARE COSIDERED IN THE SAME BONDING PAIR) The shape is also influenced by lone pairs(They are more repulsive than bonded electrons because they flare (take up more space)

  7. Different shapes • Molecules with only two atoms will always be linear • Molecules with three atoms can have two different shapes Example: BeCl2 H2O Draw the structural formula for each Why does H2O have a different shape?

  8. This molecule is linear. The H2O molecule is “bent” or “angular”

  9. Effect of the lone pairs on shape or H2O

  10. Molecules with four atoms Can have two shapes Ex: NH3 BF3 Draw each! Why do they have different shapes?

  11. This one istrigonal pyramidal because of the lone pair of electrons • This one is trigonal planar due to the absence of lone pairs on the central atom

  12. Molecules with 5 atoms If there are no lone pairs on the central atom: Ex: CH4 This is called tetrahedral

  13. Molecules with 6 atoms (and no lone pairs on the middle atom) Ex.: PCl5 This is called trigonal bipyramidal

  14. Molecules with 7 atoms and no lone pairs on the central atom Ex.: SF6 This is called octahedral

  15. Predict the shapes of these molecules • AlBr3 • PH3 • SO2

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