Molecular Shapes Computer Modeling Lab

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Molecular Shapes Computer Modeling Lab
Question:
What molecular shapes and bond angles occur for different covalent molecules?
Data:
Draw the Lewis Dot Diagram for the following molecules. You must show all work including
how you calculated the total number of valence electrons. (The molecules in bold were not
on the homework list.)
BeCl
CH
Cl
IF
2
3
3
H
O
SF
SiO
3 2-
2
6
NH
CN
Br
1-
3 1-
3
Cl
PO
ICl
3 3-
2
5
NH
PBr
CH
O
4 +
5
2
XeF
BH
NO
2 1-
4
3
Procedure:
For each of the Lewis Dot Diagrams above, use the PhET computer modeling program to “build” the
molecule and then record (in your lab notebook) both the shape of…and bond angle(s) present
in…each of the molecules.
1. Using the PhET program…click on the boxes labeled “Molecular Geometry” and “Show Bond
Angles” (do not include the electronic geometry at this time).
2. Using your LDD…”build” the molecule by clicking on the needed items in the upper right
box…the lone pair item designates a non-bonding pair of electrons.
3. Once you have the molecule “built”…record the shape name and bond angle generated by
the program. This should appear beneath each of your LDD for the list of covalent molecules
above! Be clear and legible with your work…missing or confusing dots yield an incorrect LDD.
4. The modeling program allows you to place either bonded electrons or nonbonding electrons
around a central atom. Build a molecule with four single bonds and examine the bond angle.
Now remove one of the bonded atoms and replace it with a nonbonding pair. Record the
given bond angle. Also, record your observations of the apparent sizes of the bonding pair of
electrons vs. the nonbonding pairs of electrons (the apparent volumes occupied by the
electron pairs).
5. Now (using the same example from #4 above) click on the “Electron Geometry” button and
record the molecular and electronic names listed for both of these molecules. Do this for a
number of molecules which have the same number of attachments but different bonding
pairs and nonbonding pairs of electrons and record.
6. Click on the “Real Molecules” tab. Activate all buttons and then designate H
O on the drop-
2
down menu. Toggle b/t real and model and record the bond angles. Do this for the following
molecules (which are paired with some of your earlier molecules and compare.
XeF
; BF
/BH
; ClF
/IF
; BrF
/ICl
4
3
3
3
3
5
5
Using the Table of Electronegativity Values you tape/glue into your lab book, calculate the
difference in electronegativity between all bonded atoms and indicate whether the bond is
nonpolar covalent, polar covalent, or ionic. Be sure to show all work.

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