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Molecular geometry

Lab 6. Molecular geometry. Objectives. Correlate Lewis dot structures with electron domain geometries View the effect of lone pairs of electrons on molecular shape. Materials. 5 molecular models representing the 5 basic electron domain geometries

colin-dickson
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Molecular geometry

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  1. Lab 6 Molecular geometry

  2. Objectives • Correlate Lewis dot structures with electron domain geometries • View the effect of lone pairs of electrons on molecular shape

  3. Materials • 5 molecular models representing the 5 basic electron domain geometries • 13 balloon models representing the 13 different molecular geometries

  4. How to determine the 3D structure of a molecule • Step 1: Draw the Lewis structure • Step 2: Determine electron-domain geometry around the central atom. • Step 3: Determine the molecular geometry

  5. Step 2: Determine electron domain geometry • VSEPR theory – a model used to predict the 3D structure of individual molecules. This theory is based on the idea that electrons repel each other. • Electron domain geometry describes the geometric arrangement of electrons around an atom (bonds and/or lone pair(s) of electrons).

  6. Step 2: Determine electron domain geometry • There are 5 basic electron domain geometries • Linear • Trigonal planar • Tetrahedral • Trigonal bipyramidal • Octahedral

  7. Step 3: Determine the molecular geometry • Linear • Trigonal Planar (Bent) • Tetrahedral (trigonal pyramid; bent) • Trigonal bipyramidal (Seesaw; T shaped) • Octahedral (Square pyramid; square planar) • (Show some examples and diagrams)

  8. Lab 6: Procedure/Data Collection • Station 1 – Lewis Structures and Molecular Models - 1 set of eight substances (Table 2 pg 64) are assigned (workshop handout). - In the lab, match the Lewis structure to one of the 5 molecular models on the lab bench. -(Table 3 pg 65) Identify the correct model number (and molecular formula), name the electron-domain geometry, draw the 3D structure, and label all ideal bond angles.

  9. Lab 6: Procedure/Data Collection • Station 2 – VSEPR and Balloon Models: effect of lone pairs on molecular shape. - Again, you are to match the Lewis structure (from workshop) to one of the balloon models representing VSEPR structures. -Balloons represent the space occupied by either bonding pairs or lone pairs.

  10. Station 4 – cont. • (Table 4 pg 67 & 68) • Identify the VSEPR model number • Name the molecular geometry (shape) (e.g. Bent, Seesaw, T shaped etc.) • Draw the 3D structure • Label all bond angles in your structure, indicating distortions using “<“ or “>” signs.

  11. At the end of the lab… • Turn in today’s lab write-up and all of the workshop handouts. • Lab 9 write-up, naming compounds H.W. and lab 6 (handout from last week) are due in the beginning of the lab.

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