1
Chem 301 Spring 2018 Homework Set 2 We’ll start off with a long one- 1. Derive a table of the allowed microstates for a d3 ion. Include mÒ, ms, ML and MS
and the Russell-Saunders derived term symbols. What is the term symbol for the ground state? How many microstates are there?
2. Assign point groups to the following molecules (using models sometimes
helps…definitely use the flowchart!): a.
b.
c.
d.
e.
N H
H H
2
3. Assign the following molecules to their appropriate point group. a. Cyclopropane b. SO2 c. CO2 d. B2H6 e. P4 f. Cl2C=C=CCl2 g. BF3 h. PH3 i. O2SCl2 j. OSCl2 k. B(OH)3 (planar)
l. 4. Why does SF4 have C2v symmetry instead of C4v? 5. Gauche H2O2 has C2 symmetry. What are the symmetries of the eclipsed (cis)
and anti (trans) conformations? 6. Which of the following molecules will have a dipole?
7. Using the method developed in class (with water), derive the irreducible
representations for the normal vibrations of XeF4. Determine which are IR active, which are Raman active and which are neither.
8. Derive the normal modes of vibration and their activity (IR, Raman) IF XeF4
were tetrahedral. How does this compare with the previous analysis? 9. Given the following experimental data for XeF4, is it more consistent with the D4h
or the Td structural analysis? Give reasons! XeF4 IR 123 cm-1 291 cm-1 586 cm-1 Raman 502 cm-1 543 cm-1 235 cm-1 443 cm-1
P P I
I
I
I
Cl F B
F F
F
C SS O
F F
3
10. Infrared and Raman spectra for crystalline barium rhodizonate have been reported (Baile, R. T., J. Chem. Soc., Chem. Comm., 1970, 322). From an inspection of the data, the author concludes that the rhodizonate ion, C6O62- probably has D6h symmetry. Examine the data below (given in cm-1) and explain this conclusion. 152 (IR) 275 (IR) 380(IR) 450 (Raman) 548 (Raman) 1071 (IR) 1278 (IR) 1305 (IR) 1475 (IR) 1551 (Raman)
rhodizonate anion
11. For the following molecules, determine which linear combinations of atomic orbitals on the central atom are allowed to construct sigma molecular (bonding) orbitals. a. NH3 (trigonal pyramidal) b. BF3 c. SF6 d. PF5
12. Ammonia has C3v symmetry. By constructing a multiplication table, show that the property of closure is true for the C3v point group.
O
O
O
O
O
O
2 –
