MO Theory
Problem 1: Mo diagram practice.
A) Draw the molecular orbital diagram for nitrogen. (We’ll do this one together)
i) Is it paramagnetic or diamagnetic?
ii) Draw the molecular orbital diagram for nitrogen.
iii) What would happen to the bond order if you added an electron? The bond length?
iv) What would happen to the bond order if you subtracted an electron? The bond length?
B) Draw the molecular orbital diagram for fluorine. (You’ll do this one with your neighbor)
i) Is it paramagnetic or diamagnetic?
ii) Draw the molecular orbital diagram for fluorine.
iii) What would happen to the bond order if you added an electron? The bond length?
iv) What would happen to the bond order if you subtracted an electron? The bond length?
MO Theory
n-
2
*2
4
2
C) The ground-state electron configuration of the ion C2 is 2s 2s 2p 2p .
i) What is the charge on the anion?
(hint: I told you how many electrons are in the valence shell by giving you the electron configuration,
you know how many would be there in the neutral diatomic carbon, whats the difference between
those two numbers).
ii) Draw the MO diagram of the ion.
iii) is it paramagnetic or diamagnetic?
iv) What is the bond order? Hint: ½(bonding electron-antibonding electrons)
v) Would adding an electron add or subtract from the bond order?
vi) Would subtracting an electron make the bond longer or shorter?
Problem 2: Heteronuclear diatomics. Remember, for anything other than the 2nd row homonuclear
diatomics I need to give you a hint about the ordering of the molecular orbitals. You are required to
know the second row diatomics yourself.
i) For CN the energy of the molecular orbitals follows the order of carbon (a.k.a. p2p<s2p)
ii) Draw the MO diagram.
iii) Give the valence shell electron configurations of CN and CN-.
iv) Are they paramagnetic or diamagnetic?
v) Tell the bond order of each.
vi) Which has the stronger bond?
Problem 3: Practice thinking about theoretical idea.
MO Theory
•
Consider the hypothetical species HeH. What charge, if any, should be present on this
combination of atoms to produce the most stable molecule or ion possible?
•
Draw the MO diagram for the neutral species first.
•
Decide what ion gives largest bond order
•
What is the bond order on the neutral species and what bond order, if changed, is on the ion
you chose?
•
If the charge on the neutral species were increased or decreased by one what would be the
affect on the bonding of the atom.
•
If the charge on the species you chose were increased or decreased by one what would be the
affect on the bonding of the atom.