Ionic vs. Covalent Charge Distributions
Methodology
MNDO/AM1/PM3 (Semiempirical MO)
Techniques Used
Building, Optimization, Analysis of
Bonding Parameters, Output Analysis
Abstract. You will optimize the structures of some
di-, tri-, and tetra-atomic molecules, and examine their Mulliken charge
distributions, and compare to expectations for ionic vs. covalent behavior
in the periodic table of elements.
Procedure. Using
a semiempirical method, build and optimize LiH, LiF, LiI, NaH, NaF, NaI,
BeH2, OH2, OF2, NH3, NF3,
SO2, FH, CO2. Record the Mulliken charge distributions
in the results section. Do the results correlate with your expectations
based upon the periodic table of elements? The dipole moments for diatomics
can be computed compared to experimental results, if desired.
Benchmarks.
Comparisons can be made with an periodic table listing electronegativities.
Results. Record your findings in the Table below.
| MOLECULE |
CHARGE 1 |
CHARGE 2 |
CHARGE 3 |
CHARGE 4 |
CHARGE 5 |
DIPOLE |
| Li(-)H(+) |
|
|
|
|
|
- 5.882 |
| LiF |
|
|
|
|
|
- 6.6 |
| LiI |
|
|
|
|
|
|
| NaH |
|
|
|
|
|
|
| NaF |
|
|
|
|
|
|
| NaI |
|
|
|
|
|
|
| BeH2 |
|
|
|
|
|
0.0 |
| OH2 |
|
|
|
|
|
1.8 |
| H3N |
|
|
|
|
|
1.47 |
| F3N |
|
|
|
|
|
|
| FH |
|
|
|
|
|
1.8195 |
| CO2 |
|
|
|
|
|
0.0 |
| SO2 |
|
|
|
|
|
1.63 |
Copyright 1995 by Paul M. Lahti. All Rights Reserved.