Molecular Structures

Molecular StructuresCH4Gumdrop Molecule Activity Draw the Lewis dot structure for the moleculeUse gumdrops, marshmallows, and toothpicks to build a 3D representation of the moleculeGumdrop=atomToothpick=bondSmall marshmallow=shared electron pairLarge marshmallow=lone electron pairDraw a sketch on sheet of your molecule (remember a key!)Lets look at Methane (CH4)What do you notice about methane?

How many shared electron pairs are surrounding the central carbon?Enter number into Quizdom Remote

Lets look at Methane (CH4)What do you notice about methane?

Can it bond with anything else?YesNo

Lets look at Methane (CH4)3D Model: Jmol perspectiveBond Angle: 109.5Molecular Shape Name: Tetrahedral4 pairs. All Shared.

NH3Gumdrop Molecule Activity Draw the Lewis dot structure for the moleculeUse gumdrops, marshmallows, and toothpicks to build a 3D representation of the moleculeGumdrop=atomToothpick=bondSmall marshmallow=shared electron pairLarge marshmallow=lone electron pairDraw a sketch on sheet of your molecule (remember a key!)Now, how about Ammonia (NH3)?How many shared pairs of electrons are there?

Now, how about Ammonia (NH3)?How many shared pairs of electrons are there?

Predict what you think will happen to the bond angles between the hydrogens in ammonia compared to the hydrogens in methane:A) The angle will increaseB) The angle will decreaseC) The angle will remain the same

Lets look at Ammonia (NH3)3D Model: Jmol perspectiveWith lone pairsBond Angle: 107.6Molecular Shape Name: Trigonal pyramidal4 pairs: 3 shared. 1 lone pair

What would happen if there was no Lone pair on Ammonia?

BH3For bH3 How many unshared pairs of electrons exist around the central atom?

What does BH3 look like? 3D Model: Jmol perspectiveBond Angle: 120Molecular Shape Name: Trigonal planar3 pairs: 3 shared. 0 lone pair

H2ONow Lets take another Electron pair offWhat will H2O look like? Which is NOT true about the relationship between water and ammonia? A) The bond angle is greater for water than it is for ammoniaB) The bond angle is smaller for water than it is for ammoniaC) There are more lone pairs in waterD) There are fewer shared pairs in waterH2Oits everywhere3D Model: Jmol perspectiveWith Lone PairsBond Angle: 104.5Molecular Shape Name: Bent4 pairs: 2 shared. 2 lone pair

CO2What is different for CO2?How many lone pairs are there?

What is different for CO2?How many lone pairs are there?

How many covalent bonds are formed around the carbon?

Lets look at CO23D Model: Jmol perspectiveBond Angle: 180Molecular Shape Name: Linear4 pairs: 4 shared. 0 lone pair

Easy EnoughLets see if we can use our chart to predict for other MoleculesWhat do you think about BeCl2?How many shared pairs are there?

What do you think about BeCl2?How many shared pairs are there?

How many lone pairs are there around the central atom?

Now Lets look at H2SHow many lone pairs are there?

Now Lets look at H2SHow many lone pairs are there?

What would the bond angle be?For PH3How many lone pairs are there?

For PH3How many lone pairs are there?

The bond angle for PH3 is ______ compared to CH4.A) LargerB) SmallerC) The sameHow about CCl4?How many shared pairs around central atom?

How about CCl4?How many shared pairs around central atom?

How many lone pairs?

How about CCl4?How many shared pairs around central atom?

How many lone pairs?

What would you predict the bond angle would be?PCl5Expanded Octet: PCl5Trigonal BipyramidalJmol representationBond Angles: 90 and 1205 Total Pairs: 5 Shared pairs 0 Lone Pairs

Expaned Octet Cont.Octahedral : SF6Jmol RepresentationBond Angles: 906 Total Pairs: 6 shared, 0 Lone Pairs

Octahedral : SF6What do you think would happen if you removed an Fluorine from the central Sulfur atom?

What if you removed another?

How do you think this would affect the molecular model?

Valence Shell Electron Pair Repulsion TheoryThe molecular structure is based on electrons (Shared or unshared) arranging themselves so that they have the greatest distance between one another around the central atom.

The goal is to minimize the repulsion between the negatively-charged electrons.