1 / 14

Molecular Geometry

Molecular Geometry. Background Information. We’ve done Lewis Dot representations of molecules: 2D We’ve got to go to 3D! But first, some terms. Molecular Geometry. Some Terms:. Electron Domains: The spaces electrons occupy around the nucleus of an atom. Bonding domains: shared pairs

breck
Download Presentation

Molecular Geometry

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Molecular Geometry Background Information • We’ve done Lewis Dot representations of molecules: 2D • We’ve got to go to 3D! • But first, some terms....

  2. Molecular Geometry Some Terms: • Electron Domains: The spaces electrons occupy around the nucleus of an atom • Bonding domains: shared pairs • Any bond type = 1 bonding domain • Non-bonding domains: lone pairs

  3. Molecular Geometry Some Terms - Electron Domains O H O C H C H H

  4. Molecular Geometry • VSEPR Theory Valence Shell Electron Pair Repulsion Theory - Electron domains repel each other • They push as far from each other as possible • VSEPR theory + electron domains = 3D structures

  5. Molecular Geometry One Last Thing to Keep in Mind • Not all electron domains are the same size: -Bonded electron domains are long and skinny -Due to the pull of the two nuclei -Non-bonding electron domains are short and fat -Due to the pull of one nuclei - + + - +

  6. Molecular Geometry Central Atoms with 4 Electron Domains • When four objects surround a central point, what angles are created if these objects are as far apart as possible? 109.5º angles Tetrahedral

  7. Molecular Geometry 4 Electron Domains: Tetrahedral domain geometry Molecule LDMS Bonding Angle Shape Name Non-Bonding H H C H 4 0 109.5º CH4 Tetrahedral H Trigonal Pyramid N H H <109.5º 1 3 NH3 H <109.5º H O H Bent 2 2 H2O HF Straight F H 1 3 Undefined Let’s see it! http://phet.colorado.edu/en/simulation/build-a-molecule

  8. Molecular Geometry Central Atoms with 4 Electron Domains • All of these molecules have tetrahedral domain geometries -They all have 4 electron domains • Their molecular geometries depend on the number of bonding and non-bonding domains

  9. Molecular Geometry Central Atoms with 3 Electron Domains • When three objects surround a central point, what angles are created if these objects are as far apart as possible? 120.0º angles Trigonal Planar

  10. Molecular Geometry 3 Electron Domains: Trigonal Planar domain geometry Molecule LDMS Bonding Non-Bonding Angle Shape Name H C C H 3 0 120.0º Trigonal Planar C2H4 H H 2 1 O N O NO2-1 Bent < 120.0º • Both of these molecules have trigonal planar domain geometries -They both have 3 electron domains Let’s see it! http://phet.colorado.edu/en/simulation/build-a-molecule

  11. Molecular Geometry Central Atoms with 3 Electron Domains • Their molecular geometries depend on the number of bonding and non-bonding domains • Notice that we left off the example of 1 bonding pair - Anytime there is only one bonding pair, the angle is undefined and the name is straight, regardless of the number of electron domains

  12. Molecular Geometry Central Atoms with 2 Electron Domains ●When two objects surround a central point, what angles are created if these objects are as far apart as possible? 180.0º angles Linear

  13. Molecular Geometry 2 Electron Domains: Linear domain geometry Molecule LDMS Bonding Non-Bonding Angle Shape Name 2 0 180.0º CO2 O O C Linear • Any molecule with 2 electron domains will have a linear domain geometry • Notice, again, that we didn’t include an example with 1 bonding domain Let’s see it! http://phet.colorado.edu/en/simulation/build-a-molecule

  14. Molecular Geometry Let’s Practice • Draw the LDMS for the following molecules. Then… • Identify the domain and molecular geometries • Determine the bond angle of the central atom PBr3 O2 Trigonal pyramid Straight Undefined DG = MG = Angle = O O Br Br P HCN Br H C N Tetrahedral Trigonal pyramid 107.0º DG = MG = Angle = Linear Linear 180.0º DG = MG = Angle =

More Related