CHEM231 - Problem Set #4
(Level 1 problems)
1. For the nitrate ion, NO3 _ :
a) Draw its structure as predicted by VSEPR theory.
Align the molecule in the usual way.
Hint: it will be easier if one oxygen atom is put on the negative x-axis.
b) Which valence atomic orbitals should be used as a basis set for making a MO diagram for this ion?
c) What are the symmetries of teh valence atomic orbitals of nitrogen in nitrate?
(d) Using the equations for
the calculated molecular orbitals below (i.e., Y#1-#4) draw pictures
of these four molecular orbitals in NO3 _. Bold-type
numbers are coefficients on atomic orbitals.
(Note that these four, Y#1-#4, represent only a few of the many MO’s
in this ion).
#1 = - 0.76 . 2pz (N) + 0.37 . 2pz(Oa) + 0.37 . 2pz(Ob) + 0.37 . 2pz (Oc)
#2 = 0.47 . 2pz (N) + 0.51 . 2pz (Oa) + 0.51 . 2pz (Ob) + 0.51 . 2pz (Oc)
#3 = 0.40 . 2pz (Oa) + 0.40 . 2pz (Ob) - 0.83 . 2pz (Oc)
#4 = 0.71 . 2pz (Oa) - 0.71 . 2pz (Ob)
e) Why are there four orbitals of this type?
f) What MO labels are appropriate for the four orbitals, #1-#4
Click here for all answers to this problem
2. Label the molecular orbital diagram for ammonia. Include labels for parent atomic orbitals and labels for the types of MO's.
Click here for answers to this problem
1. Using the valence atomic orbitals as a basis set, develop the MO diagram for the nitrite ion, NO2-. Include in your answer (a) linear combination of atomic orbitals for each MO (coefficients do not need to be specified) and (b) sketches of the MO’s (as best as you can manage) , (c) Attempt an assignment of bonding character (anti-, non-, etc) to the MO’s, (d) arrange the MO's in an energy diagram.
Click here for the A1 molecular orbitals
Click here for the MO diagram (color coded to MO picture borders)
