Valence Shell Electron Pair Repulsion and Molecular Polarity Simulation Activities

Instructions: Perform the two simulations below and answer all questions. You can either type in your answers in the provided spaces or handwrite your answers and then scan the file to submit in assignments

1.Phet Molecular Shapes VSEPR Simulation Activity

Introduction

Atoms bond to satisfy their need for more electrons. Most atoms will share electrons to satisfy the Octet Rule every atom wants 8 electrons to fill the s and p orbitals in the outer energy level. But, as you will see, sometimes atoms can deviate from and not follow the Octet Rule.

Because electrons have a negative charge and atoms occupy space, bonds and electrons will spread out as much as possible. Since we write in a two-dimensional plane on paper, it is difficult to visualize the true geometry of these molecules. This activity and the program you are about to use allows us to visualize on a more 3-dimensional scale.

Procedure

Log on to https://phet.colorado.edu/en/simulation/molecule-shapes either by Googling phet simulations molecule shape. Click on .

Part 1 Model Generic Molecules

Click on .

Fill in the chart below by creating the generic molecules below. On your screen in the right side click on remove all to be left with just the purple central atom. On your screen in the lower left corner, click on molecule geometry, and on electron geometry. Add atoms and electron pairs as needed to produce the generic formula. Once the molecule is assembled, click and drag the screen to spin the atom around. Click on the Show bond angles. Use the following key:

A central purple atom cannot be removed

B single bonded white atom

C double bonded white atom

D triple bonded white atom

E Electron pairs not bonded

In each box below:

1. Draw the molecule you create to the best of your ability

2. Write the Electron Geometry (EG) and the Molecule Geometry (MG) name in the box

3. Label the bond angle

4. Look at the central atom, is its octet satisfied?

Before moving on to the next molecule for each of the molecules you create: with your mouse left click/hold and move your mouse around to move the molecule and get the feel for the 3D shape.

Molecule

Molecule

AC

EG ___Linear__________________________

MG _____Linear___________Bond angle: 180 degrees_____________

Octet? ___Yes, for the central atom A, if it is a typical element that follows the octet rule, the triple bond provides it with six electrons, and it's presumed that the central atom also has another bond (possibly a hidden lone pair or implied second atom not mentioned in AC) to satisfy its octet.__

ABE3

EG ________Tetrahedral_____________________

MG ________Trigonal Pyramidal Bond Angle: Approximately 107 degrees_____________________ Octet? ____Yes, the central atom's octet is satisfied with one bond to atom B and three lone pairs._

AB3E

EG _______tetrahedral ____bond angle: 107______

MG _____trigonal pyramidal________________ Octet? ____Yes_

AB

EG ___________linear__bond angle: 180___________

MG _______linear_____________ Octet? __Yes___

ACE2

EG ______trigonal planar______bond angle: 104.5_

MG _______________bent______________ Octet? _____yes

AB2E2

EG ______ Tetrahedral_____bond angle: 104.5_______

MG _______bent______________________ Octet? _____yes

AB2C

EG __________tetrahedral, bond angle: 109.5___________________

MG ________trigonal planar_____________________ Octet? __yes___

AB3

EG _____Trigonal Planar________bond angle 120________________

MG ____Trigonal Planar_________________________ Octet? _____yes

AB4

EG ___ Tetrahedral____bond angle: 109.5___________

MG _____ Tetrahedral________________________ Octet? _____yes

ADE

EG ______linear, bond angle 180__________

MG ___linear__________________________ Octet? _____depends

Part 2 Real Molecules

Click on the Real Molecules tab at the bottom of the page. Using the pull down menu, select the molecules below and fill in the chart. Match the molecule to the generic structure above in terms of Electron Geometry EG and Molecular Geometry MG. Fill in the generic bond angles as expected according to the generic model shapes from Part 1. Fill in the True bond angles as given by the simulation.

Molecule

Generic Structure

Generic (expected) bond angles (from Part 1)

True Bond Angles

H2O

EG____Tetrahedral___________

MG_________Bent_____

104.5

104.5

CO2

EG____Linear___________

MG______Linear________

180

180

CH4

EG_____Tetrahedral__________

MG________ Tetrahedral ___

104.5

109.5

NH3

EG____ Tetrahedral...

5. Change the electronegativity of Atom B so that it is all the way to the left under less. Keep the slider for Atom A all the way under more. What happened to the bond dipole and the partial charges? It lengthened.

6. Change the electronegativities of Atom A and Atom B so that they are the same. What happens to the bond dipole and the partial charges? They disappeared.

Part 2

7. At the bottom of the screen, choose Three Atoms.

8. Under View, click the boxes so that Bond Dipoles, Molecular Dipole, and Partial Charges are all showing.

9. Without changing anything else, answer the following questions:

a. What is the molecular shape of the molecule shown? Trigonal planar

b. Which atom(s) is more electronegative? B

c. Which atom(s) has the partial negative charge(s)? B

d. Which atom(s) has the partial positive charge(s)? A, C

e. In the space below, sketch the diagram thats on the screen, including the bond dipoles, molecular dipole, and partial charges.

f. How is the molecular dipole related to the bond dipoles? It points away from them

10. Change the electronegativities of Atom A and Atom C all so that they are both all the way to the right under more. What happened to the bond dipoles, molecular dipole, and partial charges? They all reversed.

11. Click on Atom C and drag it until you make a linear molecule. What happens to the bond dipoles, molecular dipole, and partial charges? Molecular dipole disappears, bond dipoles stay the same, charges stay the same.

12. Change the electronegativity of Atom C all so that it is all the way to the left under less. What happened to the bond dipoles, molecular dipole, and partial charges? Bond dipole between B and C reverses, the molecular dipole appears from…