Shapes of 3D Molecules - Science

Shapes of 3D Molecules - Science

3D Molecular Geometry Shades and Behaviours of 3D Molecules In order to understand the shapes the molecules form we must adhere to rules that are based on the repulsion of valence shell electrons! VSEPR = Valence Shell Electron Pair Repulsion

Reasons for Geometry boils down to 5 things 1. Electrons all have the same negative charge 2. Like charges repel therefore Electrons repel 3. Bonded pairs surrounding the nucleus repel other bonded pairs and other electrons 4. Lone pairs surrounding the nucleus repel other bonded pairs and other electrons 5. Valence electrons are oriented in such a way as to be as far apart from one

another as possible For each of the following models, A WILL REPRESENT THE CENTRAL ELEMENT, X THE OUTER ELEMENT and E THE ELECTRON LONG PAIRS Shapes of 3D Molecules Molecule BeCl2

(AX2) Shape Molecular Geometry Linear

Reason for Shape The 2 pairs of bonding electrons maximize their distance from each

other 180o apart Shapes of 3D Molecules Molecule BF3 (AX3) (AX3E2)

Shape Molecular Geometry Trigonal Planar

Reason for Shape The bonding pairs must be equally far from each other The 3 bonding pairs maximize distance

from each other 120o Shapes of 3D Molecules Molecule Shape

Molecular Geometry Reason for Shape The bonding pairs must be equally far

from each other CH4 (AX4) Tetrahedral Maximize distance from each other

Shapes of 3D Molecules Molecule Shape Molecular Geometry

NH3 (AX3E) Bent Reason for Shape

Because the lone pairs are closer to the nucleus they have great repulsion, push the Hs down Shapes of 3D Molecules

Molecule H2O (AX2E2) Shape Molecular

Geometry Reason for Shape Bent The two sets of lone

pairs further push the Hs down and together Shapes of 3D Molecules Molecule Shape

Molecular Geometry Reason for Shape To maximize

distance 3 equatorial Cls are 120o PCl5 (AX5) Trigonal Bipyramidal

Top and bottom Cls are 90o apart Shapes of 3D Molecules Molecule Shape

Molecular Geometry Reason for Shape As more bonding pairs fill up locations

around the nucleus the space between the pairs becomes smaller and smaller SF6 (AX6) Octahedradron

The molecule becomes less stable due to increased repulsion Shapes of 3D Molecules Molecule

Shape Molecular Geometry Reason for Shape

Similar to Octahedradron except two lone pairs occupy the axial positions. XeF4

(AX4E2) Square Planar Whiteboarding! Grab a whiteboard and pens Form a group of 3 to 4 with people you have never worked with!

Steps to Make VSEPR Diagrams Combining two Concepts Electronegativity + Shape of the Molecule We will now combine two concepts to introduce a new one Polarity Remember Electronegativity Values

Polarity Molecules are said to be polar is the electron density is NOT evenly spread around the molecule This causes part of the molecule to be partially positive and part of the molecule to be partially negative Two Factors

1) Electronegativity 2) Symmetry of the Molecule (based on shape) Determining the Dipole + Dipole In the bonding unit we determined if a bond was polar based on the electronegativity difference of the two elements

To determine if the entire molecule is polar we must also check the symmetry (or lack there of) of the molecule Symmetry vs. Asymmetry Case 1: Non-Polar

Case 2: Polar and Asymmetric Case 3: Polar and Symmetric Polar or not polar?

Case 3: Polar and Symmetric Not Polar Case 4: Polar and Asymmetric

Polar or not polar? Case 4: Polar and Asymmetric Polar

Same Shape, Different Polarity Question to ask yourself Polar or not Polar? Does the molecule contain polar bonds, and if so, do the bond dipoles cancel each other or not? Whiteboarding!

Please collect a whiteboard and pens! Work in groups of 3 Polarity The extent of polarity depends on the size of the dipole The size of the dipole depends on the difference in electronegativities and the symmetry (or lack there of) of the molecule

Polarity When two substances have opposite polarities, they do not mix. Like mixes with Like In-Class Work Collect the Worksheet Shapes of Molecules from

the front of the class Work your way through the questions, the answers will be posted online

Recently Viewed Presentations

  • dowell.colorado.edu

    dowell.colorado.edu

    Itinerary: View your "generated" FASTQ Files. Determine the quality of our sequences. Remove poor quality or unaffiliated reads. Confirm that the libraries are of high enough quality for mapping
  • Classroom Briefing 100 200 level

    Classroom Briefing 100 200 level

    Think the V22 photos from the n:\ We help you give our warfighters the decisive edge. For 100- & 200-Level Courses. The purpose of this briefing is to provide DAU faculty with a tailorable presentation designed to provide information to...
  • ny24000063.schoolwires.net

    ny24000063.schoolwires.net

    synonyms:*modest*respectful*unassuming . humble:adjective. antonyms: *arrogant *overly proud *rude. It is important to remain humble when we get compliments. The child was not humble when he won the race. Being humble is appreciating others.
  • Financial Accounting and Accounting Standards

    Financial Accounting and Accounting Standards

    Summary of Gain and Loss Recognition on Exchanges of Non-Monetary Assets Illustration 10-20 Illustration: Santana Company exchanged equipment used in its manufacturing operations plus $2,000 in cash for similar equipment used in the operations of Delaware Company. The following information...
  • Nouns, Pronouns, Antecedents, and Agreement

    Nouns, Pronouns, Antecedents, and Agreement

    Noun Review: Common and Proper. Common nouns: a person, place, thing, or idea that is not specific or is named generally. Proper nouns: a specifically named person, place, thing, or idea. Proper nouns are capitalized . That painting is in...
  • Space News Update - August 27, 2019 In

    Space News Update - August 27, 2019 In

    The Near-Earth Asteroid Ryugu - A Fragile Cosmic 'Rubble Pile'. In this computer graphic, NASA's Voyager 1 probe, moving toward upper left, nears the edge of the sun's influence, flying through a region of space dominated by a "magnetic highway"...
  • Chapter 8

    Chapter 8

    Chapter 8 European Civilization in the Early Middle Ages, 750 - 1000
  • DBI335: Advanced Business Intelligence Solutions Using ...

    DBI335: Advanced Business Intelligence Solutions Using ...

    Setting the Sceneā€¦ Starting with Excel 2007 we invested heavily in Business Intelligence in Excel. New and redesigned BI features in Excel. Extend reach of spreadsheet beyond desktop with Excel Services