Presentation on theme: "Review Double and Triple Bonds"— Presentation transcript:
1 Review Double and Triple Bonds Make your regular Lewis Structure with all single bonds and full octetsCount up the number of electrons you used- compare it to the number of electrons you have to work withSame Number = Correct StructureNeed 2 more? Add 1 double bond and change your dotsNeed 4 more? Add 2 double bonds or 1 triple bond and change your dots
2 Intro to Molecular Structures We spent last week drawing lewis structures of covalent molecules. These are 2D representations of the molecules. Today we’re going to start talking about the actual 3D structure of the molecules.
3 Molecular Structure is determined by VSEPR VSEPR – Valence Shell Electron Pair Repulsion TheoryIt means that: Electron pairs (bonds or lone pairs) will get as far apart from each other as they can in 3D space.This happens because: Electrons are negatively charged and repel each other so they want to stay as far away as possible.
4 Molecular ShapesThe shape of the molecule depends on the number of and type of electron clouds around the central atom.Central Atom
5 Molecular Shape Electron Cloud: A group of electrons Single Bond Double Bond (1 double or triple bond =Triple Bond electron cloud)Lone pairsLone Pairs: The non-bonded electrons that finish the octet. “dots”
6 There are 5 major shapes Tetrahedral Trigonal Pyramidal Bent or V-ShapedTrigonal PlanarLinear
7 To Find the Molecular shape: Draw the Lewis StructureCount the number of bonds (remember double/triple bond = only 1 bond) on the central atomCount the number of lone pairs on the central atomMatch to the correct shape
8 You need to be able to:Match the name of the shape to the lewis structure by being able to identify the electron cloudsMatch the name of the shape to the 3D modelKnow the bond angle of each shape
9 Tetrahedral Four electron clouds All electron clouds are bonds, no lone pairsBond angle of 109.5°
10 Trigonal Pyramidal Four electron clouds 3 electron clouds are bonds 1 electron cloud is a lone pairBond angle of 107°- because lone pairs take up more room
11 Bent or V-Shaped (Option 1) Four electron clouds2 electron clouds are bonds2 electron clouds are lone pairsBond angle of 105°
12 Trigonal Planar Three electron clouds All 3 electron clouds are bonds No lone pairsBond angle of 120°
13 Bent or V-Shaped (Option 2) Three electron clouds2 electron clouds are bonds1 electron cloud is a lone pairBond angle a little less than 120°
14 Linear Two electron clouds both are bonds OR 1-4 electron clouds- only 1 bondedBond angle is 180°
15 AssignmentFind Covalent Bonds WS 1. For each molecule answer the following questions:How many electron clouds are there? How many are bonds? How many are lone pairs?Label each lewis structure with the name of the correct molecular shapeWhat is the bond angle?Covalent Bonds WS 1 is due tomorrow!When you are done keep working on Covalent Bonds WS 2 & 3 – this is due tomorrow too!
16 Giant Molecules – Look at each shape within molecule