Molecular Shapes Computer Modeling Lab (Page 2 of 2) in pdf

Data Analysis:

Using the data above, generate a sequential chart from the simplest molecule shape to the most

complex that indicates a relationship between bonded atoms to the central atom and lone pairs on

the central atom. Do not include redundant molecular shapes!

Use the following table as a guide:

Table I – Molecular Analysis

Number of

Total Number

Shape Name

Bond Angle(s)

Example

Atoms Bonded

Lone Pairs

of Attachments

Molecule

to Central

(Nonbonding

(electron

Atom

pairs) of

domains) on

electrons on

the Central

Central Atom

Atom

Bent

120°

Conclusions:

1. State in your own words the basic idea of VSEPR theory?

2. How does VSEPR relate to the different molecular shapes?

3. Examine the NH

molecule. If you analyze this molecule in two dimensions (as you have it drawn

4 +

on your paper) what bond angle and shape seems to be present? How does the actual molecule

shape and bond angle appear (based on the computer model…which is 3-D)? Explain.

4. The modeling program allows you to place either bonded electrons or nonbonding electrons

around a central atom. You “built” a molecule with four single bonds and examined the bond angle

in the procedure #4 above and then removed one of the bonded atoms and replace it with a

nonbonding pair and recorded the angle.

(a) You examined the size of the electron orbital for a bonded pair of electrons with the size of the

orbital of a nonbonding pair…what did you notice? Explain this answer.

(b) The computer modeling program is actually incorrect on the bond angle for the molecule with

three bonded pairs and one nonbonding pair (the “Real Molecules” tab is correct). Would you

expect the bond angle between bonding pairs to increase or decrease when the nonbonding pair is

placed for a bonding pair? Explain. Examine your data from procedure #6 for the “corrected bond

angles” for some of the molecules.

5. CH

Cl is a 5 atom molecule and is a perfect tetrahedron, but AsCl

, also a 5 atom molecule, is

4 -

given a different shape name. Explain.

6. BeCl

and TeCl

are both covalent molecules, yet BeCl

is linear while TeCl

is nonlinear (bent).

Explain.

7. “In molecules or polyatomic ions that contain nonbonding pairs of valence electrons on the

central atom, the electronic geometry and the molecular geometry cannot be the same. Explain

this statement using your observations from procedure step #5.

8. Distinguish between polar and nonpolar covalent bonds. Define polar vs nonpolar molecules.

Examine the Lewis Dot diagrams for Cl

and HCl…both are linear, two atom molecules.

(a) Designate the more electronegative atom in HCl. Indicate the direction the shared pair of

electrons will be more tightly held and appropriately place a (+) and (-) charge on the end of this

molecule. What about doing the same for Cl

? Explain.

(b) Now, compare BH

and NH

for polar molecule status. Explain.

Molecular Shapes Computer Modeling Lab Page 2

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