Chem 120, Experiment 3 Table In-lab worksheet
Page 1 of 4
Name:
Quiz Section No.:
PROCEDURE
In-lab worksheet
Table 1. Using Lewis structures and VSEPR to predict molecular shape:
Molecule:
Molecule’s
total
valance
electron
count:
Complete Lewis
Structure with
correct shape
according to the
VSEPR theory.
Number
of Groups
on
“central”
atom:
VSEPR
predicted
geometry of
electron
groups:
VSEPR
predicted
geometry of
molecule:
1) CO2
2) H2O
3) NH3
+
4) NH4
5) CH3Cl
6) CCl4
*Remember, the geometry of the electron groups around a central atom and the geometry of the
atoms about a central atom will be the same, when there are no lone electron pairs (so when all
electrons about the central atom are shared. A pair of electrons represents a bond).
Chem 120, Experiment 3 Table In-lab worksheet
Name:
Page 2 of 4
Quiz Section No.:
Table #2: Molecules with 4 Electron Groups about the Central Atom.
Groups
Present:
Central
Atom #1
Total
number
of groups
Draw the
correct Lewis
structure with
the 3-D shape
CH4
Electron–
pair
geometry*
Molecular
geometry**
4 single
bonds
NH3
Central
Atom #2
3 single
bonds
1 electron
pair
H2O
Central
Atom #3
2 single
bonds
2 electron
pair
In the table, "electron–pair geometry” refers to the shape you’d expect to see if all
electron pairs distributed about the central atom were visible. “molecular
geometry” refers to the shape of the molecule after distributing all electrons
(including lone pairs) then looking ONLY at the position of the atoms. For the
examples below, not all obey the octet rule, but electron totals are all as
expected. The central atoms are in bold.
Chem 120, Experiment 3 Table In-lab worksheet
Page 3 of 4
Name:
Quiz Section No.:
Table 3: Molecules with 3 Electron Groups about the Central Atom.
Groups
Present:
Central
Atom #1
Total
Number
of
Groups
Draw the correct
Lewis structure
with the 3-D
shape
BH3
3 single
bonds
SO3
Central
Atom #2
3 double
bonds
H2CO
Central
Atom #3
2 single
bonds
1 double
bond
SnCl2
Central
Atom #4
2 single
bonds
1 electron
pair
Electronpair
geometry:
Molecular
geometry:
Chem 120, Experiment 3 Table In-lab worksheet
Name:
Page 4 of 4
Quiz Section No.:
Table 4: Molecules with 2 Electron Groups about the Central Atom.
Groups
Present:
Central
Atom #1
Total
Number
of
Groups
Draw the correct
Lewis structure
with the 3-D
shape
BeH2
Electron-pair
geometry:
Molecular
geometry:
2 single
bonds
CO2
Central
Atom #2
2 double
bonds
HCN
Central
Atom #3
1 single
bond
1 triple
bond
Table 5. Drawing Lewis structures and using models to construct 3D
structures:
Chemical Formula:
Three Dimensional Representation:
Polar or
(Draw the correct Lewis structure with the 3- Nonpolar
D shape).
molecule?
CH3-CH3
H2C=CH2
Write your name on each one of the above four sheets. Staple these sheets
to the duplicate copies of the pages of your lab manual on which you wrote
down the experiment title and objective and then submit them to your TA
before leaving the lab.