CH301H - Principles of Chemistry I: Honors
Fall 2013, Unique 52195

Homework, Week 10


Homework, week 10
Answer key

1.  Construct the MO diagram for all period 2 homonuclear diatomcs (you should have already done this on your own).  For each molecule, determine the bond order, and determine whether the MO diagram gives a molecular electron configuration that is similar to or different from the prediction of the Lewis dot structure.

2.  Sketch the shapes of the sigma and pi molecular orbitals for the H2+ molecule.  Figure 6.5 in your book is a good reference, but don't just copy the figures - make sure you understand their shape.

3.  Define the sigma and pi ground state molecular orbitals.

4.  Predict which molecule has a greater bond length, H2 or He2+.  Justify your answer.

5.  Construct the MO diagram of CN.  Do your molecular orbitals give you an electron configuration that is similar to or different from the prediction of the Lewis dot structure?

6.  The bond length of the transient heteronuclear diatomic CF is 1.291 Å.  When this is ionized, the molecular ion CF+ has a bond length of 1.173 Å.  Using an argument based on the MO diagram, explain why the CF bond shortens with the loss of an electron.

7.  Fluorine gas can be ionized in the gas phase to produce F2+.  For both F2 and F2+, determine the following (you can use your MO diagram from problem 1, or redraw it for each of these species):

   a) Molecular electron configurations;
   b) Bond order;
   c) Predict which molecule has the greater bond dissociation energy.  Justify your answer.